Total peroxidase deficiency in eosinophils: a report on twin sisters, one with a refractory anaemia.

A total lack of EPO was fortuitously discovered in a 63-yr-old woman from the north of France who had primary refractory anaemia, but without dysgranulopoiesis; MPO activity was normal. Her twin sister, whose blood count was normal, also had EPO deficiency. This familial disorder was first described in the Israeli Jewish population and is very rare in Caucasians; it seems to have no pathological consequences. Microscopic studies showed no anomaly except a negativity of Sudan Black B staining which we consider to be a sign of peroxidase deficiency. Ultrastructural studies of the granules revealed normal cristalloid, but the matrix, which contains EPO in normal eosinophils, was very thin; the nature of the relation between functional and morphological anomalies has still to be elucidated.