Comparison of CMTX phenotype with intracellular localization of Cx32
| Mutation | NCV (m/sec)1-a | Symptomatic at-risk female heterozygotes | Phenotype1-b | Cellular localization of Cx32 |
|---|---|---|---|---|
| G12S | Moderate (F) to marked (M) reductions | 1 /10 | Severe | Cytoplasm |
| R15Q | 20 (M); 30 (F) | 0 /3 | Moderate | Plasma membrane |
| V63I | 41 (M) | 2 /7 | Mild | Plasma membrane and cytoplasm |
| V139M | 28–32 (M) | 9 /15 | Moderate | Plasma membrane and cytoplasm |
| R142W | 27–35 (M) | 2 /5 | Moderate to severe | Cytoplasm |
| 175fs | 26–39 (M); 37–64 (F) | 9 /29 | Severe | No detectable protein |
| E186K | 39–40 (M); 35–48 (F) | 1 /12 | Moderate | Cytoplasm |
| E208K | Not known | 1 /3 | Moderate to severe | Cytoplasm |
| R220Stop | 48–50 (M) | 2 /2 | Moderate | Plasma membrane and cytoplasm |
Moderate indicates significant weakness and atrophy of distal muscles in all limbs, high stepping gait, and early onset, but not a serious impediment to a normal lifestyle in men and high-arched feet and mild weakness and atrophy in distal legs in women.Severe indicates marked weakness and atrophy of distal muscles in all limbs, sensory loss, and significant impediments to mobility that necessitate canes and wheelchairs in men and high-arched feet and sensory disturbances in women.
↵F1-a NCV (nerve conduction velocity) is based on studies in one or more affected individuals [M (male); F (female)]; normal NCV is >50 m/sec (Nicholson and Nash, 1993).
↵F1-b Mild indicates weakness and atrophy of distal muscles in all limbs but no difficulty walking in men and thin ankles and high-arched feet in women.