Biotinidase deficiency characterized by skin and hair findings

The document describes the case of an 11-year-old Chinese girl with biotinidase deficiency (BTD), a condition that impairs the body's ability to release biotin, leading to metabolic issues, skin and hair abnormalities. The girl exhibited symptoms such as hyperkeratosis and sparse, shedding blonde hair. Laboratory tests showed low biotinidase activity at 1.168% and genetic testing revealed two heterozygous mutations in the BTD gene. After starting on a biotin supplement of 20 mg/d, her skin and hair conditions improved significantly within 1 to 3 months. The case underscores the necessity of considering BTD in the differential diagnosis of persistent dermatitis, yellow hair, and alopecia in children, and highlights the effectiveness of early biotin replacement therapy. The study also calls for universal metabolic disease screening in China and lifelong biotin supplementation for those affected, with a recommended dose ranging from 5 to 40 mg/day.