MRI findings, patterns of disease distribution, and muscle fat fraction calculation in five patients with Charcot-Marie-Tooth type 2 F disease

To describe the magnetic resonance imaging (MRI) pattern of muscle involvement and disease progression in five patients with late-onset Charcot-Marie-Tooth (CMT) disease type 2 F, due to a previously unknown mutation. Five patients (three males, two females) underwent MRI of the lower limbs to define the pattern of muscle involvement and evaluate the muscle fat fraction (MFF) of residual thigh muscle with gradient-echo (GRE) dual-echo dual-flip angle technique. Evaluation of fatty infiltration both by visual inspection and MFF calculation was performed. A proximal-to-distal gradient of muscle involvement was depicted in male patients with extensive muscle wasting of lower legs, less severe impairment of distal thigh muscles, and sparing of proximal thigh muscles. A peculiar phenotype finding was that no or only slight muscle abnormalities could be found in the two female patients. We described the pattern of muscle involvement and disease progression in a family with CMT disease type 2 F. GRE dual-echo dual-flip angle MRI technique is a valuable technique to obtain a rapid quantification of MFF.