Neutropenia among patients with adenosine deaminase deficiency
Authors: Vy Hong-Diep Kim, Anne Pham-Huy, Eyal Grunebaum
Journal: Journal of Allergy and Clinical Immunology (2018)

Adenosine deaminase (ADA) is a ubiquitous enzyme important for the degradation and salvage of adenosine (Ado) and deoxyAdo (dAdo). Autosomal-recessive defects that severely disrupt the function of ADA lead to accumulation of purine metabolites, which are toxic for rapidly proliferating cells, such as lymphocytes.1Grunebaum E. Cohen A. Roifman C.M. Recent advances in understanding and managing adenosine deaminase and purine nucleoside phosphorylase deficiencies.Curr Opin Allergy Clin Immunol. 2013; 13: 630-638Crossref PubMed Scopus (62) Google Scholar Most ADA-deficient patients present in the first year of life with profound T- and B-cell defects, leading to severe combined immunodeficiency (SCID). In addition, ADA-deficient patients frequently suffer from liver, lungs, bone, and other tissues abnormalities.1Grunebaum E. Cohen A. Roifman C.M. Recent advances in understanding and managing adenosine deaminase and purine nucleoside phosphorylase deficiencies.Curr Opin Allergy Clin Immunol. 2013; 13: 630-638Crossref PubMed Scopus (62) Google Scholar Management of ADA deficiency includes supportive care with antimicrobials such as trimethoprim/sulfamethoxazole (TMP-SMZ) and immunoglobulins. Enzyme replacement therapy (ERT) with polyethylene-glycol–conjugated ADA can improve purine homeostasis and may serve as a “bridge” until patients undergo allogeneic hematopoietic stem cell transplantation (HSCT) or gene therapy (GT). HSCT using healthy HLA-matched or mismatched family-related or unrelated donors can correct the immune and some of the systemic abnormalities.2Hassan A. Booth C. Brightwell A. Allwood Z. Veys P. Rao K. et al.Inborn Errors Working Party of the European Group for Blood and Marrow Transplantation and European Society for Immunodeficiency. Outcome of hematopoietic stem cell transplantation for adenosine deaminase-deficient severe combined immunodeficiency.Blood. 2012; 120: 3615-3624Crossref PubMed Scopus (111) Google Scholar Myelodysplasia has previously been reported among ADA-deficient patients; however, because most patients were after unsuccessful HSCT or GT, the role of the metabolic abnormality was not clear.3Sokolic R. Maric I. Kesserwan C. Garabedian E. Hanson I.C. Dodds M. et al.Myeloid dysplasia and bone marrow hypocellularity in adenosine deaminase-deficient severe combined immune deficiency.Blood. 2011; 118: 2688-2694Crossref PubMed Scopus (32) Google Scholar Here, we tested the hypothesis that ADA deficiency could be directly associated with myeloid abnormalities and neutropenia. We analyzed data from all 20 patients diagnosed at our center between January 1, 1985, and December 31, 2015, with severe ADA deficiency (enzyme activity of <2% of normal) who had a complete blood cell count with differential in the first year of life. When available, patient's DNA was sequenced for mutations in the ADA gene. Ado and dAdo (normal values <3.0 and 0.4 μmol/L, respectively) were measured before 0.5 months of life.4Al-Dirbashi O.Y. Ogrel S. McIntosh N. Higgins L. McRoberts C. Fisher L. et al.Tandem mass spectrometric determination of purine metabolites and adenosine deaminase activity for newborn screening of ADA–SCID.LymphoSign J. 2015; 2: 135-145Crossref Google Scholar HSCT was performed as previously described.5Scott O. Kim V.H. Reid B. Pham-Huy A. Atkinson A.R. Aiuti A. et al.Long-term outcome of adenosine deaminase-deficient patients—a single-center experience.J Clin Immunol. 2017; 37: 582-591Crossref PubMed Scopus (13) Google Scholar ERT using Adagen (Sigma-Tau Pharmaceuticals, Gaithersburg, Md) was administered in accordance with the manufacturer's instructions. Patient 12 received GT in Italy under a phase I/II clinical trial conducted at San Raffaele Hospital, Milan, using a Moloney murine leukemia virus-derived vector encoding ADA. Patients 18, 19, and 20, identified at birth through Ontario Newborn screening for SCID, received SIN lentivirus encoding ADA GT at the University of California, Los Angeles. When patients received multiple therapies (ie, ERT followed by GT), treatment initiation was considered as the date the first treatment was started. Neutropenia was defined as the absolute neutrophil count (ANC) of less than 6.0 × 109/L for ages 6 days or less, less than 0.5 × 109/L for ages 7 to 13 days, less than 1.0 × 109/L for ages 14 to 89 days, and less than 1.5 × 109/L for ages 90 days or more. Neutropenia was not included if it occurred only transiently after chemotherapy. Results are expressed as mean ± SD. The differences between groups and their means were assessed using the Fisher exact test and Student t test, with P less than .05 considered statistically significant. The Hospital's research ethics board approved the study (research ethics board no. 1000028108). Table I describes the characteristics of all patients included in the study. Neutropenia was identified in 13 (65.0%) of them. Apart from 5 patients (10, 17, 18, 19, 20) diagnosed with ADA deficiency immediately after birth, neutropenia was detected at a similar frequency whether patients were diagnosed before or after age 5 months (5 of 8 and 4 of 7 patients, respectively). Three patients exhibited neutropenia before 3 weeks of life, whereas in others the neutropenia was detected only at an older age, following initial normal counts (Table II). The neutropenia was often mild, yet 4 patients had an ANC of less than 0.5 × 109/L, which is considered severe. Only 3 patients had neutropenia during an ongoing infection and no patient had evidence of autoimmunity or malignancy. Neutrophil-specific antibodies were not measured. TMP-SMZ was previously implicated in causing bone marrow aplasia and neutropenia; however, in the current study, neutropenia developed in 8 ADA-deficient patients who were not receiving TMP-SMZ, whereas 7 patients treated with TMP-SMZ never developed neutropenia. In 3 patients, discontinuation of TMP-SMZ led to resolution of the neutropenia, yet 2 were also receiving ERT, and the third underwent HSCT. In 2 additional patients, the neutropenia resolved while continuing TMP-SMZ. The neutropenia resolved spontaneously in only 4 patients within 45 days, while in other patients it was corrected only after ERT or HSCT. A notable exception is patient 17, who developed neutropenia at age 3 days that did not resolve even after unconditioned HSCT from an HLA-matched sibling donor. The patient was treated with filgrastim for 2.5 years with brisk, yet only temporary increase in neutrophil counts. After discontinuing filgrastim, mild neutropenia persisted. Myeloid chimerism was not assessed in the patient, negating the ability to determine the potential benefits of myeloablative conditioning before HSCT, as is currently being used in ADA-deficient patients receiving GT.1Grunebaum E. Cohen A. Roifman C.M. Recent advances in understanding and managing adenosine deaminase and purine nucleoside phosphorylase deficiencies.Curr Opin Allergy Clin Immunol. 2013; 13: 630-638Crossref PubMed Scopus (62) Google Scholar For other ADA-deficient patients, filgrastim was not required. Evaluation of bone marrow in patients 17, 3, and 10 demonstrated adequate cellularity and normal representation of all stages of granulopoiesis without hemophagocytosis or cytogenic abnormalities. In contrast, patient 2's bone marrow assessment revealed some dyserythropoietic changes and increased megakaryocytes but normal granulopoiesis. None of the patients have developed myeloid malignancy.Table ICharacteristics of all patients diagnosed with ADA deficiency between 1984 and 2013 who had a complete blood cell count and differential documented within the first year of lifePatientSexAge ADA deficiency diagnosed (mo)ADA genotypeAdo/dAdo (μmol/L)Neutropenia in first year of life1Female2c.955_959delGAAGA and c.478+1G>A (splice site), hetero K80RNDNo2Female6NDNDYes3Female5NDNDYes4Female4Homo for c.7C>T (Q3X), homo K80RNDNo5Male12NDNDYes6Female8Homo for c.7C>T (Q3X), homo K80RNDNo7Male6NDNDNo8Male4Homo for c.7C>T (Q3X), homo K80RNDNo9Male7Homo c.424C>T (R142X)NDNo10Male<0.5Homo for c.7C>T (Q3X), homo K80RNDYes11Female6NDNDYes12Male3c.608delG and c.948C>G (S290W)NDYes13Male2c.955_959delGAAGA and c.646G>A (G216A), hetero K80RNDYes14Male3c.955_959delGAAGA and c.424C>T (R142X)21.9/40.5Yes15Female2c.424C>T (R142X) and c.955_959delGAAGA, hetero K80RNDYes16Female3c.424C>T (R142X) and c.955_959delGAAGA, hetero K80R33.4/55.2Yes17Male<0.5c.955_959delGAAGA and c.424C>T (R142X)33.0/47.3Yes18Male<0.5c.986C>T (A329V) and c.458G>T (C153F)51.3/33.7Yes19Male<0.5Homo c.955_959delGAAGA26.7/20.3Yes20Female<0.5ND4.9/25Nohomo, Homozygous; hetero, heterozygous; ND, not done. Open table in a new tab Table IIDescription and outcome of neutropenia in patients with adenosine deaminase deficiencyCharacteristicPatient23510111213141516171819Age of first CBC (d)8116297919272244370111815Age of neutropenia (d)17616299672147286807013104203Lowest ANC (× 109/L)1.080.841.200.940.660.450.250.660.500.440.110.511.1Clinical status at time of neutropeniaInterstitial p, thrushResolved pResolved pseudomonas p, UTIResolved pResolved pDisseminated CMV infectionWellResolved Klebsiella and Streptococcus pneumoniae pPJPSepsis 7 d, Escherichia coli UTI 18 d, p 24 dWellWellWellTMP-SMZ when neutropenicNoNoYesNoNoNoYesNoYesNoNoYesYesInterventionNoneNoneNoneNoneNoneNoneStop TMP-SMZNoneStop TMP-SMZNoneFilgrastimStop TMP-SMZNoneNeutropenia duration (d)1145166128∗Expired at 213 d of life while still neutropenic.28247456165†Ongoing (last assessment at age 1,460 d).18030Therapy for ADA deficiencyMRD HSCTMMRD HSCTMMRD HSCTMMRD HSCTMUD HSCTNoneERT + GTMRD HSCTMRD HSCTERTMRD HSCTERT + GTERT + GTAge at first therapy (d)205183628167316NA1091978090113640CBC, Complete blood cell count; CMV, cytomegalovirus; MMRD, HLA-mismatched related donor; MRD, HLA-matched related donor; MUD, HLA-matched unrelated donor; NA, not applicable; p, penumonia; PJP, Pneumocystis jiroveci pneumonia; UTI, urinary tract infection.∗ Expired at 213 d of life while still neutropenic.† Ongoing (last assessment at age 1,460 d). Open table in a new tab homo, Homozygous; hetero, heterozygous; ND, not done. CBC, Complete blood cell count; CMV, cytomegalovirus; MMRD, HLA-mismatched related donor; MRD, HLA-matched related donor; MUD, HLA-matched unrelated donor; NA, not applicable; p, penumonia; PJP, Pneumocystis jiroveci pneumonia; UTI, urinary tract infection. This study of a relatively large cohort of ADA-deficient patients managed at a single center demonstrates frequent neutropenia that often emerged before the effects of potential confounding factors including infections or treatments such as HSCT or GT. Thus, our study confirms that the lack of ADA directly predisposes to myeloid abnormalities. This association is further reinforced by the reports of low neutrophil counts among patients treated with cladribine (2-chloro-2′-deoxyadenosine) or pentostatin (2′-deoxycoformycin), which are potent ADA inhibitors used for T-cell suppression and hairy cell leukemia.6Andritsos L.A. Dunavin N. Lozanski G. Jones J.A. Blachly J.S. Lucas D.M. et al.Reduced dose pentostatin for initial management of hairy cell leukemia patients who have active infection or risk of hemorrhage is safe and effective.Haematologica. 2015; 100: e18-e20Crossref PubMed Scopus (5) Google Scholar Our study has several important clinical implications. ADA deficiency should be considered in infants presenting with SCID and neutropenia. Also, there are no specific predisposing factors that predict the development of neutropenia; hence, complete blood cell count should be monitored closely among all ADA-deficient patients. There is no direct correlation between the development of neutropenia and the use of TMP-SMZ, as 8 of the 13 patients were not receiving TMP-SMZ when neutropenia was detected. Moreover, when TMP-SMZ could have been the culprit, the neutropenia appeared to be transient and mild, questioning the practice of discontinuation of this important treatment. Whether the presence of neutropenia in the patients reported here could be a harbinger of impending myelodysplasia remains unanswered because it was rapidly resolved or corrected following ERT and GT or HSCT. Indeed, neutropenia and myeloid dysplasia were found in an untreated 3-year-old patient with delayed-onset ADA deficiency.7Nomura K. Hoshino A. Miyawaki T. Hama A. Kojima S. Kanegane H. Neutropenia and myeloid dysplasia in a patient with delayed-onset adenosine deaminase deficiency.Pediatr Blood Cancer. 2013; 60: 885-886Crossref PubMed Scopus (6) Google Scholar The neutropenia in ADA deficiency could be caused by a direct toxic effect of purine metabolites to bone marrow or myeloid cells, as demonstrated previously for other cells.1Grunebaum E. Cohen A. Roifman C.M. Recent advances in understanding and managing adenosine deaminase and purine nucleoside phosphorylase deficiencies.Curr Opin Allergy Clin Immunol. 2013; 13: 630-638Crossref PubMed Scopus (62) Google Scholar This hypothesis is also supported by an inverse correlation between total Ado/dAdo nucleotide levels and ANC.3Sokolic R. Maric I. Kesserwan C. Garabedian E. Hanson I.C. Dodds M. et al.Myeloid dysplasia and bone marrow hypocellularity in adenosine deaminase-deficient severe combined immune deficiency.Blood. 2011; 118: 2688-2694Crossref PubMed Scopus (32) Google Scholar High concentration of Ado might limit neutrophil migration by acting on the low-affinity A2b receptor.8Barletta K.E. Ley K. Mehrad B. Regulation of neutrophil function by adenosine.Arterioscler Thromb Vasc Biol. 2012; 32: 856-864Crossref PubMed Scopus (145) Google Scholar Hence, ADA-deficient neutrophils might not leave the bone marrow niche adequately, as also suggested by the brisk neutrophil increase in the blood observed in one of our patients following the administration of filgrastim and the poor mobilization of CD34+ cells in ADA-deficient patients.9Sekhsaria S. Fleisher T.A. Vowells S. Brown M. Miller J. Gordon I. et al.Granulocyte colony-stimulating factor recruitment of CD34+ progenitors to peripheral blood: impaired mobilization in chronic granulomatous disease and adenosine deaminase–deficient severe combined immunodeficiency disease patients.Blood. 1996; 88: 1104-1112PubMed Google Scholar Future studies will be required to further clarify the mechanism(s) leading to the myeloid abnormalities in ADA deficiency. In conclusion, we demonstrate here that neutropenia occurs frequently among adenosine deaminase-deficient patients and might be among the presenting manifestations of the disease.