Pancreatic lipomatosis in Diamond–Blackfan anemia: The importance of genetic testing in bone marrow failure disorders
Authors: John M. Gansner, Elissa Furutani, Dean R. Campagna, Mark D. Fleming, Akiko Shimamura
Journal: American Journal of Hematology (2018)

The diagnostic challenges posed by cryptic and atypical presentations of inherited bone marrow failure syndromes (IBMFS) are becoming increasingly apparent.1, 2 Here, we describe a 28-year-old gentleman who presented for a second opinion on management of his IBMFS, which had been diagnosed clinically as Shwachman–Diamond syndrome (SDS). At birth, the patient required a red cell transfusion for severe anemia (hematocrit 16.5%) attributed to a fetal–maternal bleed. Concomitant mild neutropenia and thrombocytopenia quickly resolved. At two months of age, severe anemia recurred and the patient became red cell transfusion dependent. He suffered from intermittent bouts of neutropenia, with multiple admissions for infections. By 11 months of age, the patient developed an aplastic marrow with pancytopenia and was dependent on both red cell and platelet transfusions. Testing for Fanconi anemia was negative. He was treated with high-dose steroids and had resolution of his neutropenia and thrombocytopenia but remained red cell transfusion dependent despite trials of steroids, testosterone, and splenectomy. He developed iron overload requiring chelation. Additional medical problems included chronic diarrhea with an elevated fecal fat level and intermittent adherence to pancreatic enzyme replacement, poor growth despite adequate nutrition, congenital absence of the left kidney, vesicoureteral reflux, undescended testes, ichthyosis, and developmental delay. There was no family history of bone marrow failure or cancer. On examination at age 28, he was 5 feet 4 inches tall. Laboratory values included: white cells 10.1 × 103/µL, hematocrit 25% (in the setting of transfusion), platelets 524 × 103/µL, erythropoietin 2081 mIU/ML (2.6-18.5), and ferritin 1310 ng/mL. The serum pancreatic isoamylase was 8 U/L (11-54), consistent with exocrine pancreatic insufficiency. A serum trypsin was also low at 74 ng/mL (180.5-885.3). Abdominal imaging confirmed the absence of the left kidney (Figure 1A) and showed pancreatic lipomatosis (Figure 1B). A, Congenital absence of the left kidney (the single right kidney is indicated by an arrow; the spleen is surgically absent); B, Pancreatic lipomatosis (arrowheads) Genetic testing, performed in adulthood, did not detect any mutations in the SBDS gene, which is mutated in the majority of patients with SDS.3 Instead, a heterozygous variant in RPS19, c.334dupA, p.Met112Asnfs*42 (NM_001022.3) was the sole mutation identified during sequencing of a panel of 86 genes associated with IBMFS. RPS19 is the gene most frequently mutated in Diamond–Blackfan anemia (DBA), accounting for ∼25% of cases.4 Mutations in RPS19 are known to cause disease in an autosomal dominant fashion. The c.334dupA variant results in a frameshift that creates a stop codon 41 residues downstream. This replaces the terminal 34 amino acids of the wild-type protein, including a nucleolar localization signal.5 Mitochondrial deletion and sequence analysis were normal. In this patient, the history of bone marrow failure associated with steatorrhea and pancreatic lipomatosis (Figure 1B) were consistent with a clinical diagnosis of SDS6; however, genetic testing revealed a mutation consistent with DBA. Pancreatic lipomatosis is typical of SDS but has not, to our knowledge, been reported in DBA. The patient's anemia as the primary cytopenia and congenital absence of one kidney (Figure 1A) are consistent with the diagnosis of DBA. Elucidation of the genetic basis of IBMFS carries important implications for patient care. For instance, the risk of developing leukemia is considerably higher in SDS than in DBA.7, 8 Appropriate counseling and tailored surveillance can occur when the correct diagnosis is rendered.9 This case demonstrates a relatively common problem in the evaluation of patients with IBMFS: patients who are diagnosed clinically may not undergo genetic testing. Diagnostic genetic testing can be beneficial even when the clinical phenotype is felt to be pathognomonic and also in the special situation where adults were diagnosed prior to the availability of genetic testing. This case illustrates the utility of integrating genetic testing with clinical, laboratory, and imaging assessments for IBMFS to help guide counseling and management. It also broadens the differential diagnosis for pancreatic lipomatosis to include atypical presentations of DBA. J.M.G. was supported by a career development program award from the National Institutes of Health, National Heart, Lung, and Blood Institute (K12 HL087164-10). A.S. and M.D.F. were supported by R24 DK099808-03 from the National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. E.F. was supported by T32 HL007574-36 from the National Institutes of Health, National Heart, Lung, and Blood Institute. None. J.M.G. saw the patient, prepared the figure, and wrote the first draft of the manuscript. E.F. and A.S. contributed ideas and edited the manuscript. M.D.F. contributed ideas, edited the manuscript, and arranged for mitochondrial gene sequencing. D.R.C. performed the mitochondrial gene sequencing. All authors reviewed and approved the final manuscript.