17p duplicated Charcot-Marie-Tooth 1A: characteristics of a new population.
The most frequent type of Charcot-Marie-Tooth (CMT) neuropathy is that associated with the 17p11.2-p12 chromosome duplication, whose characteristics have been well described in European and North American populations. In this study, we analyzed a Brazilian population exhibiting the mutation, found in 57 patients from 42 families (79%) of a cohort of 53 families with demyelinating CMT. Almost 20% of the duplicated cases were sporadic. In 77% of the duplicated families the mutation event occurred in the hot spot area of the CMT1A-Rep region. Forty-five percent of patients were females, 84% were Caucasians and 13% of African descent. Distal limb weakness was the most frequent abnormality, appearing in 84% of patients, although uncommon manifestations such as severe proximal weakness, floppy baby syndrome, diaphragmatic weakness and severe scoliosis were also observed. One patient was wheelchair-bound, and three suffered severe hand weakness. Sensory abnormalities were detected in 84% of the cases, but 80% were unaware of this impairment. Twelve patients complained of positive sensory manifestations such as pain and paresthesias. Progression was reported by 40%. Motor conduction velocities in the upper limbs were always less than 35 m/s, and less than 30.4 m/s in the peroneal nerve. The findings of this study expand the clinical spectrum of the disease.