Abstract • 96

Congenital dyserythropoietic anemia type II (CDA II or CDAN2) is an autosomal recessive disease, which represents the most frequent form of CDA. Like other forms it is characterized by a mild to moderate life-long anemia, ineffective erythropoiesis, and morphologic abnormalities of mature red blood cells and their precursors. The erythrocytes from patients with CDA-II showed an increased agglutinability and lysis to anti-i and anti-I sera. Bone marrow examination demonstrates five to ten times more erythroblasts than normal (erythroid hyperplasia) and about 10-40% of more mature erythroblasts are bi- or multinucleated.

Reduction in the activities of some enzymes involved in glycan synthesis and/or the amount of the corresponding messenger RNAs were reported. However, the corresponding genes were excluded as the cause of CDA II. On the other hand, the responsible gene, or the CDAN2 gene, was mapped to 20q11.2 in a set of Italian and french families. Among Italian CDA II families, there was a strong association between the CDAN2 gene and the marker D20S863, suggesting a founder effect. The institution of an International Registry for CDA-II will clarify the origin of this mutation.

Severe forms CDA II do not map to 20q 11.2, but interaction with modifying genes (such as thalassaemic genes) could explain some of these cases.