Table 2.

Distribution of the five most common CMT disease subtypes based on age of onset and physiology observed at the CMT Clinic of Wayne State University

Ulnar MNCV, m/s	Disease onset and walk-age onset	CMT subtypes	%
Very slow: ≤15	1. Childhood onset	CMT1A	68
	Walk-age onset ≥15 months	CMT1B	32
	2. Childhood onset	CMT1A	100
	Walk-age onset <15 months
	3. Adult onseta	CMT1A	100
Slow: 15< and ≤25	1. Childhood onset	CMT1A	88
	Walk-age onset ≥15 months	CMT1B	6
		CMT1X males	6
	2. Childhood onset	CMT1A	98
	Walk-age onset <15 months	CMT1X males	2
	3. Adult onseta	CMT1A	94
		CMT1B	3
		CMT1X males	3
Slow: 25< and ≤35	1. Childhood onset	CMT1A	67
	Walk-age onset ≥15 months	CMT1X males	33
	2. Childhood onset	CMT1A	55
	Walk-age onset <15 months	CMT1B	3
		CMT1X males	42
	3. Adult onseta	CMT1A	88
		CMT1B	6
		CMT1X males	6
Intermediate: 35< and ≤45	1. Childhood onset	CMT1X males	100
	Walk-age onset ≥15 months
	2. Childhood onset	CMT1B	17
	Walk-age onset <15 months	CMT1X males	41
		CMT1X females	17
		HNPP	25
	3. Adult onseta	CMT1B	55
		CMT1X males	18
		CMT1X females	18
		HNPP	9
Normal: >45	1. Childhood onset	CMT1X females	33
	Walk-age onset ≥15 months	CMT2A	33
		HNPP	33
	2. Childhood onset	CMT1B	3
	Walk-age onset <15 months	CMT1X males	9
		CMT1X females	15
		CMT2A	15
		HNPP	58
	3. Adult onseta	CMT1B	28
		CMT1X males	7
		CMT1X females	26
		CMT2A	2b
		HNPP	37

CMT Charcot-Marie-Tooth; HNPP hereditary neuropathy with liability to pressure palsies; MNCV motor nerve conduction velocity

^aAdult onset: If symptoms onset was ≥ third decade of life

^bAll patients with CMT2A have more severe phenotypes compared with the other patients with childhood onset who began walking before 15 months of age

Patients with unobtainable compound muscle action potential amplitudes in the upper extremities were not included in this table