Biotinidase deficiency characterized by skin and hair findings.

Biotinidase deficiency is a rare hereditary metabolic disease. Only a few cases have been reported in China, almost all of which have been in the pediatric population. We report a case of a girl with characteristic skin and hair findings with a negative family history, although her grandparents were consanguineous. The metabolites in the proband's blood and urine increased prominently, and the percentage of biotinase was 1.168%, much lower than normal. Genotyping identified two heterozygous mutations, which were C.1457T>A (p.L486Q) and C.1491dupT (p.L498Ffs*13) in the BTD gene. The diagnosis of biotinidase deficiency was established. No relevant reports about the missense mutation at the mutation site C.1457T>A (p.L486Q) of the BTD gene have been retrieved. Biotin replacement therapy was administered in the dose of 20 mg/d. The dermatitis subsided after 1 month, and the hair color was almost normal after 3 months. This reminds dermatologists to include biotinidase deficiency in their clinical differential when faced with children's intractable dermatitis, yellow hair, and alopecia.