Three siblings presented in early childhood with central-nervous-system (CNS) dysfunction, candida dermatitis, keratoconjunctivitis, and alopecia. Two were studied immunologically and had absent delayed-hypersensitivity skin-test responses and absent in-vitro lymphocyte responses to candida antigen. One of them had selective IgA deficiency and no antibody response to pneumococcal polysaccharide immunisation, and the other had a subnormal percentage of T lymphocytes in peripheral blood. The first two siblings died with progressive CNS deterioration and overwhelming infection. The third child, who presented with a periorificial candida dermatitis, alopecia, keratoconjunctivitis, and intermittent ataxia at eighteen months of age, had intermittent lactic acidosis and raised excretion of β-hydroxypropionate, methylcitrate, β-methylcrotonylglycine, and β-hydroxyisovalerate in urine. After four days of oral biotin, 10 mg/per day, the metabolites in her urine were significantly reduced, suggesting a biotin-responsive multiple carboxylase deficiency. These findings, taken with previous reports of immune defects in patients with disorders of branched-chain aminoacid catabolism, suggest a new biochemical basis for primary immunodeficiency disease.
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