ERYTHROCYTOSIS DUE TO A MUTATION IN THE ERYTHROPOIETIN RECEPTOR GENE

Familial erythrocytosis, associated with high haemoglobin levels and l ow serum erythropoietin (Epo), has been shown to co-segregate with a s equence repeat polymorphism at the 5' region of the erythropoietin rec eptor (EpoR) in a large Finnish family. We have investigated the cause of erythrocytosis in an English boy. Sequencing of the cytoplasmic re gion of the EpoR detected a de novo transition mutation of G to A at n ucleotide 6002. This mutation resulted in the formation of a stop codo n at amino acid 439 with the loss of 70 amino acids from the carboxy t erminus. The mutation (G6002A) has arisen independently in a Finnish f amily and de novo in this English boy. Patients with unexplained eryth rocytosis and low serum Epo levels should be investigated for EpoR mut ations.