EARLY DIAGNOSIS OF SEVERE COMBINED IMMUNODEFICIENCY SYNDROME

Infants with severe combined immunodeficiency syndrome (SCIDS) have a greatly improved prognosis if diagnosed and treated before they develo p overwhelming infection. Clinical and laboratory data on 45 patients with SCIDS were retrospectively reviewed to assess the value of absolu te lymphocyte counts in making an early diagnosis. Ninety infants matc hed for age, sex, and presenting symptoms were used as controls. Thirt een (29%) infants with SCIDS were diagnosed at birth as previous sibli ngs had been affected; 32 (71%) were diagnosed after the development o f symptoms. Eighteen (56%) of these remained undiagnosed until after 6 months of age. The first symptoms occurred at a median of 5 weeks (ra nge 1 day to 8 months) and the first admission to hospital was at 4 mo nths (range 1 week to 16 months). Symptoms included respiratory infect ion (91%), vomiting and diarrhoea (81%), failure to thrive (88%), cand idiasis (50%), and skin lesions (28%). The mean lymphocyte count was 1 .71 x 10(9)/1 compared with 7.2 x 10(9)/1 in controls. Excluding one c hild with Omenn's syndrome (lymphocyte count 23.3 x 10(9)/1), all symp tomatic infants with SCIDS had lymphocyte counts less than 2.8 x 10(9) /1 at presentation. The median delay between the first abnormal lympho cyte count and diagnosis was seven weeks (range one day to 13 months). Twenty eight (88%) of 32 infants would have been diagnosed before 6 m onths of age if investigated after the first low lymphocyte count. The se data indicate that low lymphocyte counts are predictive of SCIDS. P aediatricians are urged to pay attention to the absolute lymphocyte co unts in all infants in whom a full blood count is performed. Those wit h lymphocyte counts persistently less than 2.8 x 10(9)/1 should be inv estigated for SCIDS.