Forgotten, but not gone

A boy born post-term weighing 3.6 kg with normal Apgar scores was noticed to have generalised skin petechiae at birth but no other obvious clinical abnormalities. On investigation, he had thrombocytopenia (platelet count 29×10⁹/l), but other haematological markers were normal. He was discharged after bacterial sepsis and alloimmune thrombocytopenia had been excluded. Unfortunately there was not sufficient blood available to investigate for congenital viral infections. Thrombocytopenia resolved spontaneously at age 16 days (platelet count 176×10⁹/l).

The infant was readmitted at 10 weeks of age for poor feeding, diarrhoea, and occasional vomiting. On examination he was found to be pale and thin; weight was at the 4th percentile. He had mild hepatosplenomegaly, a soft systolic murmur, mild anaemia (haemoglobin 98 g/l), and slightly abnormal results on liver function tests (aspartarte aminotransferase 75 U/l, alanine aminotransferase 97 U/l, and alkaline phosphatase of 602 U/l). There was no evidence of hepatitis B surface antigen, hepatitis A IgM, hepatitis C IgG, toxoplasma IgA, or IgG antibodies in serum. Cytomegalovirus and parvovirus B19 IgG were detected in serum, suggesting either passive transfer of maternal antibodies or past infection. Interestingly, rubella IgM antibody was strongly positive in serum and rubella IgG was also positive.

The infant’s mother recalled attending hospital at 11 weeks’ gestation with fever, swollen left knee, and a macular rash starting on the face and spreading to the trunk and abdomen, which was considered to be a drug reaction.