Congenital Dyserythropoietic Anemia Type I Due to Biallelic CDAN1 mutations: Report from the Congenital Dyserythropoietic Anemia Registry (CDAR)

Congenital dyserythropoietic anemias (CDA) are rare hereditary diseases of abnormal erythropoiesis. The CDA Registry of North America (CDAR) (NCT02964494) was opened in 2016 to investigate the natural history and molecular biology of CDA. CDA type I (CDA-I) is a recessive form of CDA characterized by macrocytic anemia, hemolysis with inadequate reticulocytosis, and iron overload. The bone marrow shows binucleated erythroblasts with chromatin bridges by light microscopy and spongy heterochromatin in erythroblasts by electron microscopy. The phenotypic heterogeneity in presentation and course of CDA-I is remarkable. Most CDA-I cases are caused by biallelic mutations in CDAN1or C15orf41, and 10-20% do not have an identifiable mutation. Non-hematological features, especially skeletal features, were historically reported in 10-20% of patients (Wickramasinghe, 1998). Due to the rarity of CDA-I and its clinical overlap with several disorders, the diagnosis is often missed or delayed by up to 17 yrs (median) (Roy, 2019). We describe in this study the characteristics and clinical course of CDA-I patients due to CDAN1 mutations enrolled in CDAR.

Patients with a phenotypic diagnosis of CDA and their family members were enrolled in CDAR. Clinical and demographic data were gathered from participants at study entry and updated periodically thereafter. Participants elect to give blood, bone marrow, and DNA samples to the biorepository associated with CDAR. Participants with a phenotypic diagnosis of CDA-I and confirmed mutations in CDAN1 were included in this study.

Six participants had a diagnosis of CDA-I due to biallelic CDAN1 mutations, comprising 18% (6/33) of affected CDAR participants. CDAN1 mutations were found in 75% of cases diagnosed phenotypically as CDA-I. All six participants presented early in life with a variable degree of non-immune hemolysis, and the diagnosis was confirmed within a median of 2 years from presentation. The characteristics of participants are summarized in table 1. Two had family history of stillbirth or fetal demise in older siblings due to hydrops fetalis. One participant presented prenatally with fetal anemia and started intrauterine transfusions at 24 weeks of gestation; 2 presented with severe anemia and signs of hydrops, pulmonary hypertension, transaminitis, severe hyperbilirubinemia, and thrombocytopenia at birth; and 3 presented with neonatal jaundice and moderate anemia.

All participants required blood transfusions in the neonatal period. Three had spontaneous improvement and did not require transfusions after the first year of life. One remained transfusion-dependent at last follow up at the age of 4 yrs. One became transfusion-independent after starting interferon-alpha at 1 yr of age and did not need further transfusions even after discontinuation at 3 yrs of age. One had splenectomy at 11 y.o because he was misdiagnosed to have a membrane disorder but presented in adulthood with hemolytic anemia and pulmonary hypertension and was diagnosed at that time with CDA-I by genetic sequencing.

All participants had one or more non-hematological manifestations, including hypertrophic skin folds, onychocryptosis, curved toenails, syndactyly, café-au-lait spots, macrocephaly, spinal fusion, scoliosis, and short stature. One participant suffered a thalamic stroke in the postnatal period, 2 had transient neonatal pulmonary hypertension in the setting of severe anemia, and one had pulmonary hypertension post-splenectomy in adulthood. Ferritin was high in all participants at last follow up, and 4 received chelation therapy.

In summary, mutations in CDAN1 are the most common identified mutations in CDAR. CDA-I causes early-onset macrocytic anemia, which may present prenatally, with variable severity of hemolysis ranging from hydrops to mild neonatal jaundice and anemia. Non-hematological manifestations, mainly skeletal, nail and skin abnormalities are more common in CDA-I than previously reported, and their presence in infants with unexplained anemia should raise suspicion for the diagnosis. The availability of molecular testing has significantly accelerated the diagnosis. Management of patients with CDA-I requires multidisciplinary approach from an early age to improve outcome. Collaboration between clinicians, scientists, patients, and families is needed to advance the understanding and treatment of this rare disease.

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