Sir.—I was interested to see in the Journal (132:78-86, 1978) the recent review of infectious mononucleosis by Rapp and Hewetson. A few years ago in the Journal (128:239-243, 1974), we reported a fatal case of infectious mononucleosis in a child who was an exception to some of the remarks made by Rapp and Hewetson. Our patient was only 2 years old but had heterophil titers (unadsorbed) as high as 1:1,792. He subsequently developed Reye's syndrome, not to our knowledge previously described and not mentioned by Rapp and Hewetson as either a neurologic or hepatic complication. Remarkably, he recovered from the Reye's syndrome but then fell victim to granulocytopenia, a complication of infectious mononucleosis that Rapp and Hewetson did describe. However, he died in septic shock, in spite of vigorous intravenous antibiotic treatment. The hematologic complications of infectious mononucleosis may be transient and reversible, but they are not necessarily benign.