A family with X-linked inheritance and Pelizaeus-Merzbacher-like disease (PMLD), PMD without the proteolipid protein (PLP) mutation, studied at the UMDNJ-Robert Wood Johnson Medicial School, New Brunswick, NJ, had a new locus on Xq chromosome, more than 10 cM away from PLP. A clinical diagnosis of PMD in the proband was made on the X-linked inheritance, congenital onset, nystagmus, slow progression with pyramidal signs, seizures, and psychomotor deterioration. The patient died at 25 years, and neuropathological study showed calcific vasculopathy in the basal ganglia and dentate nucleus and intact myelin. 
COMMENT. PMD patients having mutations in the PLP gene have an onset of symptoms in early infancy, nystagmus, spastic diplegia, ataxia, titubation, head bobbing, hypotonia, and mental retardation. Classical type I PMD has ‘tigroid’ or perivascular preserved myelin and a life span up to 25 years, whereas type II PMD has diffuse demyelination and death before 10 years of age. The above report identifies a kindred with PM-Like D, clinically resembling PMD, but with intact myelin and with mutations at a new locus on the X chromosome.