Differentials for our patient's presentation include HSP (the official abbreviation is SPG), MTHR deficiency, multiple sclerosis, spinocerebellar ataxia, cervical/lumbar spondylosis, arginase deficiency, vitamin B-12/vitamin E/copper deficiency, lathyrism, HTLV-1, Friedrich's ataxia, Krabbe's disease, ALS, PLS, metachromatic leukodystrophy, or adrenoleukodystrophy (see Table 1). The gene discussed is SPRR2A; the disease is adrenoleukodystrophy.