[Erythroblastopenia in a child with immune deficiency and hyper IgM]

The authors report the case of a boy with a history of recurrent infections, who presented with erythroblastopenia at age 5 years. An immune deficiency with hyper IgM was found. Erythroblastopenia appeared to be related to a serum inhibitor of erythropoiesis. This inhibitor was present in the serum IgM fraction and acts by blocking the erythropoietic activity of a soluble substance in the serum, which is not erythropoietin but which could be a cofactor of this hormone. A series of 5 plasma exchanges, performed in 10 days, permitted to clear the inhibitor and induced remission, still persisting after a 12 month follow-up.