[Genetic study of congenital afibrinogenemia. Review of 12 cases].

Twelve cases of congenital afibrinogenemia in 11 families are reported. A family study was performed in six cases. The parents were genetically related in 8 of the 11 families. In half the cases another sibling had the disease. In every case the direct ascendants were unaffected. On the basis of results of plasma fibrinogen assays, "unprotected" heterozygotes with no more than 2.5 g/l fibrinogen and "protected" heterozygotes with normal fibrinogen levels were differentiated. Identification of "unprotected" heterozygotes is essential for genetic counselling. The reason for this variable phenotypic expression of congenital afibrinogenemia is unclear.