A 7-year-old girl presented with complaints of hair loss and a known partial biotinidase deficiency since birth. Biotin supplementation was discontinued after the first year of life because clinical manifestations were absent, and laboratory findings were normal. At age 2 years, hair loss and eczema occurred. Owing to low biotinidase activity, biotin supplementation, 20 mg/wk, was restarted, but it was again discontinued at age 3 years because normal biotin levels had been achieved once more.