The underlying genetic cause for Dominant Intermediate CMT-A has not yet been identified by scientists, but they have narrowed it down to chromosome 10q24.1 – q25.1. Despite not knowing the exact genetic cause, evidence strongly suggests that this type of CMT is inherited in an autosomal dominant pattern.
CMTDIA appears to be affecting only one Italian family. Published literature includes a case study of this family in 1985, 1998, and again in 2001. This family included 15 CMTers in the most recent case study.
The CMTers ranged in age from 7 to 72 years, they each had onset of symptoms by the time they were 20 years old, and their CMT was slowly progressive. Each experienced lower limb weakness, lower limb muscle cramps, and difficulty walking and running. Later in life, they each developed severe weakness and atrophy of lower leg muscles and intrinsic hand muscles. They each developed steppage gait, pes cavus, areflexia, and mild sensory loss. However, nobody in the family became wheelchair dependent despite disease severity in their legs.