CMT2L is caused by autosomal dominant mutations in the HSPB8 gene. To date, only one family has been identified to have CMT2L.
In 2005, scientists identified a very large Chinese family who was extensively affected by a unique type of CMT. Each CMTer in the family has experienced symptom onset between their mid-teens and early their 30’s. Symptoms start with weakness developing first in the muscles of the lower legs then in the hands. Progression is slow over time. This family’s CMT was found to be caused by the mutation mentioned, and this family’s CMT is labeled CMT2L.