Court Opinion

ID: 6346507
Source: CourtListenerOpinion
Date Created: 2022-06-03 14:02:37.908421+00
Date Added: 2024-06-11T15:49:21.394234
License: Public Domain

Case: 21-1866   Document: 38     Page: 1   Filed: 05/20/2022

   United States Court of Appeals
       for the Federal Circuit
                 ______________________

 T.S., BY AND THROUGH HIS PARENTS, GERMAIN
          SANCHEZ, JENNIFER SANCHEZ,
                Petitioners-Appellants

                            v.

       SECRETARY OF HEALTH AND HUMAN
                   SERVICES,
               Respondent-Appellee
              ______________________

                       2021-1866
                 ______________________

    Appeal from the United States Court of Federal Claims
 in No. 1:11-vv-00685-PEC, Judge Patricia E. Campbell-
 Smith.
                 ______________________

                 Decided: May 20, 2022
                 ______________________

     LISA A. ROQUEMORE, Law Office of Lisa A. Roquemore,
 Rancho Santa Margarita, CA, argued for petitioners-appel-
 lants.

     HEATHER LYNN PEARLMAN, Vaccine/Torts Branch, Civil
 Division, United States Department of Justice, Washing-
 ton, DC, argued for respondent-appellee. Also represented
 by BRIAN M. BOYNTON, C. SALVATORE D'ALESSIO, JENNIFER
 LEIGH REYNAUD.
                  ______________________
Case: 21-1866    Document: 38     Page: 2    Filed: 05/20/2022

 2                                                 T.S.   v. HHS

     Before MOORE, Chief Judge, BRYSON and DYK, Circuit
                          Judges.
      Opinion for the court filed by Chief Judge MOORE.
      Dissenting opinion filed by Circuit Judge BRYSON.
 MOORE, Chief Judge.
     Trystan Sanchez appeals a decision of the United
 States Court of Federal Claims that sustained a special
 master’s decision denying Trystan compensation under the
 Vaccine Act. Sanchez v. HHS, 152 Fed. Cl. 782, 784 (2021).
 For the following reasons, we reverse and remand.
                        BACKGROUND
                              I
     On February 5, 2009, Trystan Sanchez, then a six-
 month-old baby, had a well-child check with Dr. Philip
 Brown. Dr. Brown gave Trystan multiple vaccines, includ-
 ing the DTaP-HepB-IPV vaccine. Hours later, Trystan de-
 veloped a fever of 102.2°F and was crying a loud, high-
 pitched cry, as if he was in pain. Trystan was inconsolable
 and developed a hot lump on his left thigh. Trystan’s fever
 fluctuated over the next few days.
     On February 15, 2009, Trystan’s fever returned, and he
 became congested. The next night, his fever rose to
 103.2°F, and he cried loudly in a high pitch. When
 Trystan’s father was able to calm him, he would startle
 awake as if he could not breathe. Trystan kicked and
 jerked as if he did not want to be held. Trystan also exhib-
 ited arm contortions, holding his arms stiffly behind his
 back. When his father would try to straighten his arm, it
 would snap back.
     On February 17, 2009, Trystan’s mother took him to
 urgent care where he saw Jonathan Luna, a physician as-
 sistant. Mrs. Sanchez later testified that she told Mr. Luna
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 T.S.   v. HHS                                                 3

 about the arm contortions, but Mr. Luna’s notes do not
 mention them. Mr. Luna diagnosed Trystan with a “com-
 mon cold” and “viral syndrome.”
     According to his family’s testimony, Trystan’s arm con-
 tortions continued during the period immediately following
 February 16. Trystan’s father, mother, and paternal
 grandmother all testified that his arm contortions occurred
 often multiple times a day during this period. J.A. 630–33;
 J.A. 518; J.A. 530–31, 578; J.A. 466, 476. See also J.A. 596–
 97 (Trystan’s maternal grandmother testifying that she
 witnessed an arm contortion in late February 2009).
      At his one-year exam in August 2009, Micaela Marin-
 Tucker, a physician assistant, noted Trystan was develop-
 mentally behind and could not stand, crawl, grasp, hold his
 head up while sitting, or attempt to move his lower extrem-
 ities. His mother stated that she noticed a change in his
 development approximately two to three months earlier.
 At this appointment, Trystan received his next round of
 vaccinations. Mr. Sanchez testified that shortly thereafter,
 his arm contortions returned.
     Trystan proceeded to have muscle spasms, develop-
 mental delays, seizures, dystonia, 1 and other neurologic is-
 sues for the next few years. For years, the precise nature
 of Trystan’s illness eluded his doctors. Trystan was even-
 tually diagnosed with Leigh’s syndrome in late 2014.
 Leigh’s syndrome is a severe neurological disorder that of-
 ten presents in the first year of life, is characterized by pro-
 gressive loss of mental and movement abilities, and
 typically results in death within “a couple years.” J.A. 40.

        1Dystonia is characterized by involuntary muscle
 contractions that cause repetitive movements or abnormal
 postures and is caused by neurological abnormality or dam-
 age. J.A. 2816.
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 4                                                 T.S.   v. HHS

 Genetic testing showed that Trystan has two disease-caus-
 ing mutations associated with Leigh’s syndrome.
                              II
      In October 2011, Mr. and Mrs. Sanchez petitioned for
 compensation under the Vaccine Act, 42 U.S.C. § 300aa–1
 et seq. Despite all the contrary family testimony, and with-
 out discussing that testimony, a special master found that
 Trystan did not have arm contortions until months after
 his February 2009 vaccination. J.A. 686. However, in his
 later decision denying compensation, the special master re-
 versed course, crediting Mr. Sanchez’s testimony that
 Trystan had arm contortions on February 16. J.A. 2297
 (“[O]n February 1[6], 2009, . . . [h]is arms contorted and he
 was jerking around.”). But the special master also found
 that those contortions were a symptom of Trystan’s cold,
 not Leigh’s syndrome, and that the first sign of Trystan’s
 Leigh’s syndrome, the start of “a neurologic decline,” likely
 did not occur “until May 1, 2009, at the earliest.” J.A. 106.
 And because of this multi-month delay in the development
 of symptoms, the special master found it more likely than
 not that the vaccine was not a substantial factor in
 Trystan’s Leigh’s syndrome. The Claims Court affirmed.
      The Sanchezes appealed to this court, and we vacated
 and remanded, holding that the record did not support the
 special master’s finding that Trystan’s arm contortions
 were a symptom of a cold. Sanchez v. HHS, 809 F. App’x
 843, 852–53 (Fed. Cir. 2020) (non-precedential). In re-
 manding, we instructed the special master to (1) address if
 Trystan’s arm contortions on February 16, 2009 were evi-
 dence of a seizure or dystonia and thus a sign of a neuro-
 logic injury; (2) revisit causation and provide a complete
 analysis of all prongs of the causation analysis; and (3) ad-
 dress if Trystan’s genetic mutations were the sole substan-
 tial cause of his Leigh’s syndrome, including if the timing
 and severity of Trystan’s Leigh’s syndrome would have
 been the same absent the vaccine. Id. at 853–54.
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 T.S.   v. HHS                                               5

      On remand, the special master ordered supplemental
 status reports, directed the parties to provide updated
 medical records, and allowed the parties to supplement
 their expert reports. Based in part on that new evidence,
 the special master found that Trystan’s arm contortions on
 February 16 were not a neurologic abnormality caused by
 his vaccination or manifestations of a neurological disor-
 der. Again, the special master denied compensation, this
 time on two grounds: (1) Trystan did not experience neuro-
 logic deterioration until many weeks after his February
 2009 vaccination and (2) the Secretary established that
 Trystan’s two genetic mutations solely caused his Leigh’s
 syndrome. The Claims Court sustained the special mas-
 ter’s decision. Mr. and Mrs. Sanchez appeal. We have ju-
 risdiction under 28 U.S.C. § 1295(a)(3).
                         DISCUSSION
      In Vaccine Act cases, we review the Claims Court’s de-
 cisions de novo, “applying the same standard of review that
 court applied in reviewing the special master’s decision.”
 Milik v. HHS, 822 F.3d 1367, 1375–76 (Fed. Cir. 2016). Ac-
 cordingly, we review the special master’s legal conclusions
 de novo and his findings of fact under an arbitrary-and-ca-
 pricious standard. Althen v. HHS, 418 F.3d 1274, 1277–78
 (Fed. Cir. 2005); Porter v. HHS, 663 F.3d 1242, 1249 (Fed.
 Cir. 2011).
     To prove causation in fact, 2 a claimant must show: (1) a
 medical theory causally linking the vaccine and the injury;
 (2) a logical sequence of cause and effect showing the vac-
 cine was the reason for the injury; and (3) a proximate tem-
 poral relationship between vaccination and injury. Althen,
 418 F.3d at 1278. If the claimant meets this burden, he is

        2Trystan is required to show causation in fact be-
 cause his claim is “off table,” i.e., a claim not listed in 42
 U.S.C. § 300aa-14.
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 6                                                 T.S.   v. HHS

 entitled to compensation unless the government demon-
 strates that the injury was caused by factors unrelated to
 the vaccine. 42 U.S.C. § 300aa–13(a)(1)(B).
                              I
      The special master’s determination that Trystan failed
 to prove causation in fact turned entirely on his finding
 that Trystan’s February 16 arm contortions were a one-off
 event. Based on that finding, the special master concluded
 that the contortions were not a symptom of a neurologic
 injury, that “Trystan did not start a neurologic decline un-
 til May 1, 2009, at the earliest” (months after his February
 2009 vaccination), and, thus, that Trystan failed to satisfy
 Althen prongs two and three. That finding, however, was
 arbitrary and capricious. On the record before us, the only
 reasonable conclusion is that Trystan’s arm contortions
 continued after February 16 and were a symptom of a neu-
 rologic injury.    Accordingly, Trystan satisfied Althen
 prongs two and three and established causation in fact. 3
     There is no dispute that Trystan has Leigh’s syndrome
 and that neurodegeneration is a result of Leigh’s syn-
 drome. J.A. 40. There is likewise no dispute that dystonia
 (like Trystan’s arm contortions) or seizures can be a mani-
 festation of Leigh’s syndrome. J.A. 96. Trystan was vac-
 cinated February 5, 2009 and had a cold on February 16,
 2009. The special master found, based exclusively on
 Trystan’s family’s testimony, that Trystan had arm contor-
 tions (a seizure-like experience) on February 16, 2009,
 shortly after his vaccination. J.A. 2297. The special mas-
 ter also found, based entirely on family testimony, that
 Trystan was experiencing arm contortions in August 2009
 consistent with Leigh’s syndrome: “Some information
 about Trystan’s health before the second set of vaccinations
 comes from his family’s testimony about his behavior

     3   That Trystan satisfied prong one is not in dispute.
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 T.S.   v. HHS                                              7

 during the baby shower on August 9, 2009. This testimony
 credibly established that Trystan lacked muscle tone and
 was having arm contortions.” J.A. 108 (emphasis added).
 There is no dispute that by August of 2009 his significant
 developmental delays associated with his Leigh’s syn-
 drome were observed and documented. J.A. 687; Oral Arg.
 at 30:20–31, 34:28–35:05.
      Despite the February arm contortions, the special mas-
 ter found “that Trystan’s neurodegeneration began around
 May 1, 2009” rather than in February. J.A. 107. The spe-
 cial master’s entire conclusion hinged upon his finding
 that: “there appears to be no evidence that between Febru-
 ary 17, 2009, and at least May 1, 2009, that Trystan suf-
 fered a seizure or stroke-like episode. Trystan did have
 arm contortions of February 16, 2009. But, that episode
 was short-lived, singular, and did not signify a neurologic
 injury due to vaccination.” J.A. 102. The special master
 explained, “it seems unlikely that Trystan would experi-
 ence an episode of dystonia that is caused by an injury in
 his basal ganglia one time in February 2009 and not expe-
 rience any other motor problems for months.” J.A. 98. The
 government’s expert, Dr. Raymond, testified that “[i]f
 Trystan were having arm contortions in February 2009 due
 to Leigh[’s] syndrome and basal ganglia injury, they would
 have been persistent.” J.A. 98.
     This entire case turns on a single fact finding by the
 special master. The special master found the family’s tes-
 timony that Trystan had arm contortions on February 16,
 2009 credible. The special master also found that Trystan
 had arm contortions beginning August 9, 2009 (and contin-
 uing thereafter), again based entirely on the family’s testi-
 mony, which he expressly found to be credible. However,
 the special master rejected the testimony from the same
 family members that the arm contortions continued
 throughout the relevant period from February 16 to May 1.
 And he did so with no particular explanation as to how the
 former claims regarding arm contortions (February 16 and
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 8                                                 T.S.   v. HHS

 August 9) were credible and the identical testimony from
 the identical witness that there were additional arm con-
 tortions between February and May was somehow not
 credible. Such an inconsistent, unfounded, and entirely
 unexplained fact finding is arbitrary and capricious.
     The relevant record evidence shows that Trystan’s con-
 tortions persisted after February 16. Mr. Sanchez testified
 that Trystan continued to have arm contortions multiple
 times a day in the days, weeks, and months following Feb-
 ruary 16. J.A. 630–33. Mrs. Sanchez similarly testified
 that Trystan continued to have arm contortions in the
 months following the February 16 contortions—sometimes
 “five to ten times a day.” J.A. 518, accord J.A. 530–31, J.A.
 578.     Trystan’s paternal grandmother testified that
 Trystan had arm contortions “approximately three times a
 day” from February to August. J.A. 466; J.A. 476.
 Trystan’s maternal grandmother testified that approxi-
 mately two to three days after February 16, she witnessed
 Trystan contorting his arm when she was attempting to
 put him in his car seat and she was unable to place his arm
 behind the seat buckle. J.A. 596–97. And Trystan’s aunt
 testified that when she saw him at a family event in March
 2009, he was “so hard [and] so stiff.” J.A. 495. None of this
 testimony was rebutted. Moreover, medical records from
 November 12, 2009, and August 2, 2010, albeit non-con-
 temporaneous with the events in question, corroborate the
 family’s testimony. J.A. 308, 362. There was no contrary
 record evidence.
      The only reasons the special master articulated for dis-
 crediting the family’s testimony were that it conflicted with
 “[t]he absence of notation [of arm contortions] in any of the
 contemporaneous medical records” and the general asser-
 tion that “memories dim with the passage of time.” J.A.
 683. Given the record in this case, such a conclusion is ar-
 bitrary and capricious.
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 T.S.   v. HHS                                                9

      To be sure, the special master was not required to
 credit this testimony simply because there is no contrary
 evidence in the record. See, e.g., Anderson v. City of Besse-
 mer City, N.C., 470 U.S. 564, 575 (1985) (“[A witness’] story
 itself may be so internally inconsistent or implausible on
 its face that a reasonable factfinder would not credit it.”);
 cf. Trade Well Int’l v. United Cent. Bank, 825 F.3d 854, 861
 (7th Cir. 2016) (“A district court need not have contrary ev-
 idence to discredit a witness.”). However, the special mas-
 ter here provided no sound basis for discrediting the
 extensive family testimony regarding the relevant time pe-
 riod between February and May where he expressly cred-
 ited much of this same testimony at other times. 4 And
 contrary to the Secretary’s arguments, see Oral Arg. at
 19:20–20:20, 22:45–28:40, 32:25–34:00, no contemporane-
 ous medical record mentioned the February 16 contor-
 tions. 5 These fact findings cannot be reconciled.

        4 The notes from the visit with Ms. Marin-Tucker in
 August 2009 indicating that Ms. Sanchez only noticed de-
 velopmental changes approximately 2–3 months earlier do
 not contradict the substantial family testimony establish-
 ing that Trystan’s arm contortions occurred in an even ear-
 lier period.
      5   Our court explained in Kirby v. HHS, 997 F.3d
 1378 (Fed. Cir. 2021), “As the Claims Court has recognized,
 physicians may enter information incorrectly and ‘typically
 record only a fraction of all that occurs.’” Id. at 1383 (quot-
 ing Shapiro v. HHS, 101 Fed. Cl. 523, 538 (2011)). We
 agreed with the Claims Court that “the absence of a refer-
 ence to a condition or circumstance is much less significant
 than a reference which negates the existence of the condi-
 tion or circumstance.” Id. In this case, none of the early
 medical records mention the arm contortions, but the spe-
 cial master nonetheless found them to have begun on Feb-
 ruary 16, 2009.
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 10                                                T.S.   v. HHS

     This is an unusual case where a remand is unnecessary
 because here the special master’s finding of arm contor-
 tions on February 16, 2009 (and his associated credibility
 determination) is law of the case. The government did not
 challenge this fact finding in the prior appeal. The earlier
 findings stand and the special master’s findings that there
 were no arm contortions in the relevant period between
 February and May cannot be reconciled with his earlier de-
 terminations.
     Given the record and the prior findings, there is no ba-
 sis to reject the evidence that Trystan was experiencing
 arm contortions throughout the relevant period. It neces-
 sarily follows that Trystan’s contortions were a sign of a
 neurologic injury because the Secretary’s expert witness
 and the special master acknowledged as much. The Secre-
 tary’s expert witness, Dr. Raymond, gave unrebutted testi-
 mony that persistent arm contortions are symptomatic of a
 neurologic injury. J.A. 98 (“If Trystan were having arm
 contortions in February 2009 due to Leigh[’s] syndrome
 and basal ganglia injury, they would have been persistent
 and obvious.”). And the special master relied entirely upon
 the alleged lack of persistent contortions to find that the
 contortions were not a sign of neurologic injury. Id. (“[I]t
 seems unlikely that Trystan would experience an episode
 of dystonia that is caused by an injury in his basal ganglia
 one time in February 2009 and not experience any other
 motor problems for months.”). The record provides no al-
 ternative explanation for persistent contortions nor did the
 government argue for any.
     Because those contortions began within two weeks of
 his vaccinations, Trystan has shown a logical chain of
 cause and effect between his vaccination and his neuro-
 degeneration. See J.A. 75 (“[I]f . . . Trystan developed neu-
 rodegeneration within a short time (approximately two
 weeks) after the vaccination, then a ‘logical’ conclusion
 might    be    that    the     vaccination      caused    the
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 T.S.   v. HHS                                              11

 neurodegeneration.”). Therefore, Trystan has satisfied his
 burden of showing Althen prongs 2 and 3.
                               II
     As Trystan has met his burden, he is entitled to com-
 pensation unless the Secretary establishes the injury was
 due to factors unrelated to the vaccine. 42 U.S.C. § 300aa–
 13(a)(1)(B). In that regard, the special master found that
 Trystan’s genetic mutations were the sole substantial
 cause of his Leigh’s syndrome.
     There is no evidence, however, that Trystan’s muta-
 tions would have resulted in the same progression and se-
 verity of his Leigh’s syndrome absent the vaccine. The
 special master merely cited a reference describing a child
 with similar mutations who developed Leigh’s syndrome
 and concluded Trystan’s Leigh’s syndrome would manifest
 the same way. J.A. 129–34. At the outset, a single example
 does not establish the typical progression of a disease and
 is not “sufficient to disprove a medical theory that a vaccine
 can cause aggravation in some patients.” Sharpe v. HHS
 964 F.3d 1072, 1084 (Fed. Cir. 2020). Moreover, the cited
 reference provides no information on how the subject’s dis-
 ease progressed after manifestation, and the subject’s
 Leigh’s syndrome presented at nine months of age. J.A.
 126–27. So, at best, the reference merely shows Trystan
 would have developed Leigh’s syndrome at nine months of
 age absent the vaccine. That says nothing about what
 caused Trystan’s Leigh’s syndrome to manifest at six
 months of age or to progress the way it did. Thus, the gov-
 ernment did not meet its burden to establish Trystan’s
 Leigh’s syndrome was the result of factors unrelated to the
 vaccine.
                         CONCLUSION
     In sum, Trystan has proven causation in fact, and the
 government has failed to overcome that showing. Accord-
 ingly, Trystan is entitled to compensation under the
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 12                                               T.S.   v. HHS

 Vaccine Act. We reverse the decision denying compensa-
 tion and remand to the special master for the sole issue of
 damages.
                REVERSED AND REMANDED
                           COSTS
 Costs to Trystan.
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    United States Court of Appeals
        for the Federal Circuit
                   ______________________

  T.S., BY AND THROUGH HIS PARENTS, GERMAIN
           SANCHEZ, JENNIFER SANCHEZ,
                 Petitioners-Appellants

                              v.

       SECRETARY OF HEALTH AND HUMAN
                   SERVICES,
               Respondent-Appellee
              ______________________

                         2021-1866
                   ______________________

    Appeal from the United States Court of Federal Claims
 in No. 1:11-vv-00685-PEC, Judge Patricia E. Campbell-
 Smith.

 BRYSON, Circuit Judge, dissenting.
     The National Childhood Vaccine Injury Act empowers
 the special masters who adjudicate claims under the Act to
 exercise broad discretion in evaluating the merits of those
 claims. Congress’s intent to vest such discretion in the spe-
 cial masters is reflected in our standard of review, which
 empowers the Court of Federal Claims—and by extension,
 this court—to overturn a special master’s decision only
 when the decision is “arbitrary, capricious, an abuse of dis-
 cretion, or otherwise not in accordance with law.” 42
 U.S.C. §§ 300aa-12(e)(2)(B), 300aa-12(f); see also Munn v.
 Sec’y of Health & Hum. Servs., 970 F.2d 863, 870 (Fed. Cir.
 1992) (noting that the arbitrary-or-capricious standard is
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 2                                                   T.S.   v. HHS

 “well understood to be the most deferential possible”). The
 court today overturns the special master’s factual findings
 as unsupported. I believe that there is sufficient evidence
 in the record to support the special master’s findings, and
 that those findings are not arbitrary or capricious.
     In vaccine injury cases, “[w]e do not reweigh the factual
 evidence, assess whether the special master correctly eval-
 uated the evidence, or examine the probative value of the
 evidence or the credibility of the witnesses—these are all
 matters within the purview of the fact finder.” Porter v.
 Sec’y of Health & Hum. Servs., 663 F.3d 1242, 1249 (Fed.
 Cir. 2011). If the special master’s findings are “based on
 evidence in the record that was not wholly implausible, we
 are compelled to uphold that finding as not being arbitrary
 or capricious.” Lampe v. Sec’y of Health & Hum. Servs.,
 219 F.3d 1357, 1363 (Fed. Cir. 2000). Most importantly,
 we do not “second guess” the special master’s conclusions,
 especially where “the medical evidence of causation is in
 dispute.” Cedillo v. Sec’y of Health & Hum. Servs., 617 F.3d
 1328, 1338 (Fed. Cir. 2010). In light of those principles, the
 majority opinion does not give the special master’s decision
 the deference it is due.
                               I
      At the outset, it is important to note that Trystan
 Sanchez was born with two genetic mutations that caused
 him to develop Leigh’s syndrome, a mitochondrial disorder
 affecting the central nervous system. In infants with those
 mutations, Leigh’s syndrome typically manifests following
 a stressor, often a viral infection, within the first 12 months
 of life. J.A. 2309. Both parties’ experts agreed that the
 mutations predisposed Trystan to developing Leigh’s syn-
 drome, but the Sanchezes argued that the stressor that
 caused the onset of Leigh’s syndrome was the series of vac-
 cinations that Trystan received on February 5, 2009. J.A.
 47, 118. The question presented by this case is whether
 Trystan’s vaccinations triggered the onset of his Leigh’s
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 T.S.   v. HHS                                               3

 syndrome, or whether that condition, to which he was ge-
 netically predisposed, was triggered by another stressor,
 such as one of the periodic colds that he suffered between
 February and June of 2009.
      The focus of the majority’s analysis is on whether the
 evidence showed that Trystan manifested signs of a neuro-
 logical injury within days of his February 5, 2009, vaccina-
 tions. The evidence showed (and it is not disputed) that on
 February 16, 2009, Trystan was suffering from a cold.
 Trystan’s father testified that while he was trying to com-
 fort Trystan that evening, Trystan contorted his arms and
 arched his back in an unusual manner. The question that
 was the subject of much attention during the evidentiary
 proceedings was whether Trystan’s arm contortions on the
 evening of February 16, 2009, were indicative of neurolog-
 ical injury or were consistent with the cold from which he
 was suffering at the time.
                               A
     Dr. Gerald Raymond, one of the government’s experts,
 addressed the relationship between the arm contortions
 and Trystan’s cold. In his report, which was in evidence in
 this case, Dr. Raymond stated that “[t]he events in Febru-
 ary around the time of the six month evaluation are more
 consistent with a viral [upper respiratory infection] and not
 myoclonic jerks.” J.A. 1101. In a supplemental report, Dr.
 Raymond added that Trystan’s arm contortions were “con-
 sistent with an uncomfortably ill child who is tired and
 does not want to be held.” J.A. 2737. The special master
 found Dr. Raymond to be credible and his statements about
 Trystan’s actions on the night of February 16, 2009, to be
 persuasive evidence that Trystan’s behavior on that night
 was not indicative of a neurological injury.
     The special master’s finding that Trystan’s arm contor-
 tions were an isolated event and not evidence of the onset
 of Leigh’s syndrome is further supported by other evidence
 in the record. First, after seeing Trystan for a cold on April
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 4                                                 T.S.   v. HHS

 29, 2009, pediatrician Nabil A. Seleem noted that Trystan
 “exhibited no neurological symptoms.” J.A. 220. Second,
 at a visit on May 13, 2009, another pediatrician, Philip S.
 Brown, similarly did not report any neurological symp-
 toms. J.A. 686–87. Third, at an appointment with physi-
 cian’s assistant Micaela Marin-Tucker in August 2009,
 Trystan’s mother reported that “she noticed a change in
 [Trystan’s] development about 2–3 months ago,” i.e., in
 May or June of 2009. J.A. 222. Notably, that statement in
 Ms. Marin-Tucker’s report is inconsistent with Trystan’s
 mother’s testimony at the hearing before the special mas-
 ter, where she testified that Trystan’s arms contorted
 “around five to ten times a day” between February 17,
 2009, and April 29, 2009. J.A. 518.
     In addition to those medical reports, the special master
 considered Dr. Raymond’s expert opinion regarding the
 likelihood that the arm contortions were a manifestation of
 a neurological injury. Dr. Raymond noted that “[i]f Trystan
 were having arm contortions in February 2009 due to
 Leigh[’s] syndrome and basal ganglia injury, they would
 have been persistent and obvious and it is expected that
 his attentive parents would have brought it to the attention
 of his providers as they did for his other illnesses.” J.A.
 2737–38. Dr. Raymond further stated that arm contortions
 behind the infant’s back manifesting dystonia would not be
 possible “without appropriate myelination,” which, in his
 view, would have been unlikely at six months of age. J.A.
 97.
                              B
     To be sure, there is evidence in the record that could
 support a contrary conclusion, particularly the testimony
 from family members regarding Trystan’s behavior during
 the interval between February and May 2009. See, e.g.,
 J.A. 362, 476, 518, 597, 630–33, 717. In addition, the peti-
 tioners’ expert, Dr. Lawrence Steinman, testified that “arm
 contortions” can be “intermittent” and “are not a
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 T.S.   v. HHS                                               5

 manifestation of the common cold.” See J.A. 2813–14. But
 those conflicts in the evidence were for the special master
 to resolve, and the special master’s decision to credit the
 evidence that pointed away from the petitioners’ theory
 that Trystan’s neurological injury manifested itself shortly
 after his vaccinations was not arbitrary or capricious.
      Nor was it arbitrary or capricious for the special master
 to credit the testimony of Trystan’s father that Trystan was
 contorting his arm on the night of February 16, 2009, but
 not to accept the testimony of Mr. Sanchez and other family
 members that Trystan’s arm contortions continued during
 the months immediately following that incident. It is well
 established that a fact finder is entitled to “accept those
 portions of a witness’s testimony which it considers credi-
 ble and reject other portions which it finds to be improba-
 ble.” See Rixey v. W. Paces Ferry Hosp., Inc., 916 F.2d 608,
 616 (11th Cir. 1990); see also United States v. Boyce, 564
 F.3d 911, 916 (8th Cir. 2009); United States v. Ware, 577
 F.3d 442, 447 (2d Cir. 2009); United States v. Dozier, 162
 F.3d 120, 125 (D.C. Cir. 1998); United States v. De Leon
 Ruiz, 47 F.3d 452, 454 (1st Cir. 1995); United States v. Col-
 ston, 936 F.2d 312, 315 (7th Cir. 1991); United States v.
 Cueto, 628 F.2d 1273, 1275 (10th Cir. 1980); Conway v.
 Chem. Leaman Tank Lines, Inc., 610 F.2d 360, 367 (5th
 Cir. 1980); Carothers v. Rhay, 594 F.2d 225, 229 (9th Cir.
 1979); NLRB v. Boyer Bros., 448 F.2d 555, 561 (3d Cir.
 1971); People v. Mendoza-Balderama, 981 P.2d 150, 157–
 58 (Colo. 1999) (collecting cases). And as this court has
 previously noted, a special master’s “assessments of the
 credibility of the witnesses” are “virtually unchallengeable
 on appeal.” Lampe, 219 F.3d at 1362.
     In particular, it was within the province of the special
 master not to credit the lay testimony of the family mem-
 bers where it was in tension with contemporaneous medi-
 cal records, Dr. Raymond’s expert opinion, and other
 evidence in the case. As to the events of February 16, 2009,
 the special master credited Dr. Raymond’s assessment that
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 6                                                   T.S.   v. HHS

 Trystan’s behavior could be explained by the discomfort
 caused by his cold. The special master found the father’s
 testimony regarding the events of that night to be generally
 plausible and not indicative of the onset of a neurological
 injury. The special master also credited the family mem-
 bers’ testimony that Trystan experienced arm contortions
 in August 2009 and that those manifestations of dystonia
 were accompanied by significant developmental delays.
     As to the family members’ testimony that Trystan ex-
 perienced continuous arm-contortion incidents between
 February and May of 2009, however, the special master
 found that testimony to be in conflict with other evidence
 in the record. He did so in his initial decision denying com-
 pensation, J.A. 2297–98, and he adhered to those findings
 in his decision following the remand from this court, J.A.
 99–107. In light of the record evidence, the special master’s
 conclusions were reasonable. For instance, in their con-
 temporaneous reports, Drs. Seleem and Brown, who saw
 Trystan in late April and mid-May 2009, did not note the
 presence of arm contortions or any other neurological
 symptoms. Nor did their reports reflect that Trystan’s par-
 ents mentioned the arm contortions.
     It is true that, in general, “the absence of a reference to
 a condition or circumstance is much less significant than a
 reference which negates the existence of the condition or
 circumstance.” Kirby v. Sec’y of Health & Hum. Servs., 997
 F.3d 1378, 1383 (Fed. Cir. 2021). However, the fact that
 neither doctor’s contemporaneous report makes any refer-
 ence to arm contortions or any other neurological symp-
 toms and that those reports did not reflect that Trystan’s
 parents mentioned Trystan’s arm contortions is probative
 of whether the contortions continued after the evening of
 February 16, 2009. That is especially true in light of Dr.
 Raymond’s testimony that arm contortions due to Leigh’s
 syndrome and basal ganglia injury would have been persis-
 tent and obvious, and that if Trystan were experiencing
 arm contortions attributable to those conditions, his
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 T.S.   v. HHS                                              7

 parents likely would have raised that issue with the pedi-
 atricians during their visits in April and May 2009.
     Of the evidence relied upon by the special master, the
 report of Ms. Marin-Tucker regarding her interview with
 Ms. Sanchez during Trystan’s pediatric visit in August
 2009 is of particular significance. Ms. Marin-Tucker’s
 notes reflected that Trystan’s mother said she had first
 noted a change in Trystan’s development in about April or
 May of 2009. That observation, which was made closer in
 time to Trystan’s vaccinations than any of the family’s later
 testimony, suggests that Trystan’s condition did not mani-
 fest itself until well after his February 2009 vaccinations.
      On the surface, the reports of other physicians who as-
 sessed Trystan’s condition after August 2009 appear to cor-
 roborate the family’s testimony about Trystan’s behavior in
 the weeks following his February 2009 vaccinations. How-
 ever, those reports regarding the events of early 2009 were
 based on histories obtained from Trystan’s parents, not on
 the firsthand observations of the treating physicians. See
 J.A. 95, 362. For that reason, it was reasonable for the spe-
 cial master not to attach independent significance to those
 reports regarding the timing of the onset of Trystan’s con-
 dition.
                              II
     In summary, given the competing evidence regarding
 the etiology of Trystan’s condition, it was not unreasonable
 for the special master to conclude that Trystan’s Leigh’s
 syndrome did not manifest itself until significantly later
 than the date of his February 2009 vaccinations, and there-
 fore that no causal relationship was established between
 the vaccinations and the triggering of Trystan’s Leigh’s
 syndrome. J.A. 117. There is ample evidence in the record
 consistent with those findings. Even if we were applying a
 “substantial evidence” standard of review, we would be
 obliged to sustain the special master’s decision. A fortiori,
 the special master’s weighing of the evidence cannot fairly
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 8                                                 T.S.   v. HHS

 be considered arbitrary or capricious. Moreover, nothing
 in the special master’s analysis was contrary to law, and
 there is no suggestion that he selectively ignored particular
 evidence. The majority disagrees with the special master’s
 conclusion regarding causation in this case. But that is not
 enough to justify concluding that the special master’s deci-
 sion was arbitrary or capricious. Accordingly, I would up-
 hold the decision of the Court of Federal Claims affirming
 the special master’s decision.