Infectious mononucleosis and agranulocytosis.

Infectious mononucleosis is often complicated by haematological abnormalities but agranulocytosis is so rare that a causal relationship has been questioned. We here describe 2 sisters, 3 and 5 years old, who both developed agranulocytosis or profound granulocytopenia 4-5 weeks after the acute onset of mononucleosis. No contributory cause could be found and we conclude that a constitutional disposition may be responsible for this complication.