Gene dosage is the number of copies of a gene and the amount of product they make. Disease can result from too little dosage (haploinsufficiency) or too much (a duplication or overexpression). The clearest CMT example is CMT1A, caused by a duplication of PMP22 that adds a third copy and overexpresses the protein; the reciprocal deletion causes the milder HNPP.
A Name That Does Too Much Work
Jean-Martin Charcot's name appears throughout medicine, but nowhere does it create more confusion than in the foot. Learn why the CMT foot and Charcot neuroarthropathy, also known as Charcot foot, share a name yet differ in how they develop, appear, and are managed.
