Normalization of low biotinidase activity in a child with biotin deficiency after biotin supplementation.

We report findings in a Japanese boy with severe skin rash attributable to biotin deficiency. The patient had an intracranial malformation and developed biotin deficiency due to tube feeding with a single formula for over one year. Results of urinary organic acid analysis were consistent with multiple carboxylase deficiency, and low biotinidase activity was also observed. After biotin supplementation, the skin rash improved and biotinidase activity normalized. We speculate that biotin is one regulating factor in the biosynthesis of biotinidase.