Congenital dyserythropoietic anemia type I (CDA I) is characterized by moderate-to-severe macrocytic anemia presenting occasionally in utero as severe anemia associated with hydrops fetalis but more commonly in neonates as hepatomegaly, early jaundice, and intrauterine growth restriction. Some individuals present in childhood or adulthood. After the neonatal period, most affected individuals have lifelong moderate anemia, usually accompanied by jaundice and splenomegaly. Secondary hemochromatosis develops with age as a result of increased iron absorption even in those who are not transfused. Distal limb anomalies occur in 4%-14% of affected individuals.

Congenital dyserythropoietic anemia type IIIb (CDAN3B) is an autosomal recessive disorder characterized macrocytic anemia, aberrant giant multinucleated erythroblasts in the bone marrow, and skull defects secondary to severe anemia with ineffective erythropoiesis (summary by Hernandez et al., 2023). For a general description and a discussion of genetic heterogeneity of CDA, see CDAN1 (224120).