We have evaluated a young woman with segmental spinal muscular atrophy, who has a deletion of a portion of the long arm of chromosome 18. She also has vitiligo and lichen sclerosis et atrophicus. She has neither the facial dysmorphism nor the mental deficit usually associated with the 18q- syndrome. Magnetic resonance imaging scan of her brain demonstrates high signal intensity consistent with abnormal myelination. Southern blot analysis of her DNA demonstrates that the deletion includes the gene for human myelin basic protein. Neither spinal muscular atrophy nor this patient's skin manifestations have been previously reported in association with 18q-.