β‐Mannosidase deficiency: Heterogeneous manifestation in the first female patient and her brother

Summary β‐Mannosidase deficiency was demonstrated in fibroblasts of a girl who showed severe psychomotor retardation, bone deformities and gargoylism and recurrent skin and respiratory infections and who died at 20 years of age from bronchopneumonia. This first demonstration of a female patient confirms the autosomal recessive inheritance of β‐mannosidosis. Further investigation of this gipsy family revealed β‐mannosidosis in an older brother with a milder manifestation of gargoyl facial dysmorphology, mental retardation, hearing impairment and recurrent infections. β‐Mannosidase activity was completely deficient in his cultured skin fibroblasts, leukocytes and plasma. In urine a characteristic disaccharide was present. Heterozygote levels of β‐mannosidase were found in fibroblasts and/or plasma of the parents and one sister.