Unremarkable neonatal period followed by
hypotonia and slowing of motor development, starting at age 4 to 6 months.
Although some patients can walk, by age 10 to 13 years they are
wheelchair-bound or bed-bound. Areflexia, paraparesis, psychosis, and
seizures are observed. Other features include diffuse hypotonia, absence of
deep tendon reflexes, flexion contractures in the metacarpophalangeal
joints, low-set thumbs, pes equinovarus, hammertoe deformity, syndactyly of
the toes, and sensory neuropathy in a glove and stocking distribution.
Progressive scoliosis becomes apparent with older age and may lead to
severely restrictive lung function. Moderate mental retardation with an IQ
ranging from 45 to 60 in the majority of cases.