Chapter 446 Congenital Dyserythropoietic Anemias
The congenital dyserythropoietic anemias (CDA) are a heterogeneous class of genetic disorders characterized by unique morphologic abnormalities in marrow erythroblasts: multinuclearity, abnormal nuclear fragments, and intrachromatin bridges between cells, associated with ineffective erythropoiesis. Three major types of CDA (types I, II, and III) are defined (see 
Table 446-1 on the Nelson Textbook of Pediatrics website at www.expertconsult.com), although additional subgroups and variants have also been identified. These rare disorders are characterized by variable degrees of anemia, increased marrow erythroid activity (ineffective erythropoiesis), and secondary hemochromatosis.
Type I Congenital Dyserythropoietic Anemia
Pathogenesis
Type I CDA is an autosomal recessive disorder. A causative gene (CDAN1) has been localized to chromosome 15q15, and several different mutations have been identified. This gene encodes codanin-1, a protein that has been identified as a cell cycle–dependent nuclear protein whose synthesis is promoted by the transcription factor E2F1. Its exact cellular role remains to be elucidated. Notably, not all CDA-1 cases are linked to chromosome 15q15, implying that at least one other locus must exist.
Clinical Manifestations
The onset of macrocytic anemia and/or jaundice may be noted at any age, although most cases are first recognized during childhood or adolescence. Rarely, type 1 CDA is diagnosed in utero. Symptoms can include splenomegaly, hepatomegaly, gallstones, and mild jaundice. Type I CDA has been associated with skeletal (primarily syndactyly) and other dysmorphologies. Symptoms of iron overload and, in more severe cases, evidence of extramedullary hematopoiesis in frontal or parietal bones of the skull, may be present.
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