Recessive Intermediate CMT-D is caused by autosomal recessive mutations in the COX6A1 gene. Symptoms usually occur very early in life and can be quite severe. CMTers who have CMTRID are usually wheelchair bound by their mid-teens, and there are reports of cerebral atrophy and developmental delays. Severe foot deformities are common with CMTRID.
Nerve conduction characteristics of CMTRID more closely resemble that which is seen in Type 2 CMT, and some have argued that this type should be reclassified as a Type 2 CMT.