Peter was born after an uneventful pregnancy and weighed 3.1 kg. At 3 months, he developed otitis media and an upper respiratory tract infection. At the ages of 5 months and 11 months, he was admitted to the hospital with Haemophilus influenzae pneumonia. The infections responded promptly to the appropriate antibiotics on each occasion. When 16 months old, he developed balanitis. He is the fourth child of unrelated parents; his three sisters show no predisposition to infection. Examination at the age of 18 months showed a pale, thin child whose height and weight were below the third centile. There were no other abnormal features. He had been fully immunized as an infant (at 2, 3, and months) with tetanus and diphtheria toxoids, whole-cell pertussis, Haemophilus conjugate vaccine, and oral polio. In addition, he had received measles, mumps, and rubella vaccine at 12 months. All immunizations were uneventful. Immunological investigations into the cause of his recurrent infections showed severe panhypogammaglobulinemia with absent antibody production. Although there was no family history of hypogammaglobulinemia, the absence of mature B lymphocytes in his peripheral blood strongly supported a diagnosis of 27222. His antibody deficiency was treated by 2-weekly intravenous infusions of human normal IgG in a dose of 400 mg/kg body weight per month. Over the following years, his health steadily improved. His weight and height are now on the 10th centile, and he has had only one episode of otitis media in the last 18 months. Table C3.1 Immunological investigations Quantitative serum immunoglobulins (gn)