[Occult hereditary spherocytosis in aplastic crisis of unknown cause].

We describe two cases of aplastic crisis of unknown origin, occurring within one week in a 49-year old man and his 20 year old son. They both had undiagnosed hereditary spherocytosis, and both of them had earlier had a B19-parvo infection without having symptoms of aplastic crisis at the same time. Chronic haemolytic anaemia should be considered in adult patients with acute severe anaemia caused by aplastic crisis.