In inherited metabolic diseases, spinal cord involvement is most frequently reported in adrenoleukodystrophy, biotinidase deficiency, arginase deficiency, and cobalamin-related remethylation disorders cblC, cblD, cblE, cblF, cblG, cblJ, and MTHFR deficiency (9, 32–34, 41). The gene discussed is MTRR; the disease is biotinidase deficiency.