Serum thymidine kinase in congenital dyserythropoietic anaemia type III.

Serum thymidine kinase (TK) was determined in a family with congenital dyserythropoietic anaemia type III (CDA, type III). 20 patients and 10 of their healthy siblings were investigated. Elevated TK was found in all 20 patients (median 56.2 U) but their healthy siblings had normal values (median 2.65 U). We suggest that determination of TK should be used for discrimination between healthy siblings and individuals affected by CDA type III when bone marrow examination is not suitable.