Congenital dyserythropoietic anaemia type 1 (CDA I) is an autosomal recessive disorder of erythropoiesis characterized by a clinical picture of anaemia secondary to ineffective erythropoiesis, haemolysis and striking morphology of erythroid precursors (inteternuclear chromatin bridges, spongy heterochromatin, invaginations of nuclear membrane) and erythrocytes (macrocytosis, anisocytosis, basophilic stippling) in the bone marrow and peripheral blood smears, respectively. The aim of this work was to 1) collect patients and characterize this rare disease, 2) understand the genetics of CDA I using linkage analysis, 3) identify the CDAN1 gene mutations and finally 4) to study the molecular perturbations which lead to dyserythropoiesis.