Charcot-Marie-Tooth (CMT) disease, an inherited peripheral neuropathy of sensory and motor nerves, is one of the most common neurological disorders, affecting about 1 in 2500 individuals. However, its subtype CMT4B3 has so far been reported in only two families worldwide. CMT4B3 symptoms start to appear during adolescence or early adulthood. Initial symptoms include distal lower extremity weakness and atrophy, syndactyly and pes planus of the feet with a progression towards upper limb weakness. Patients may become immobile by the third or fourth decade of life. The disease can also result in distal sensory impairment, areflexia and facial weakness. Nerve conduction velocities are markedly reduced and nerve biopsies may show depleted myelinated axons or focally folded myelin.    

CMT4B3 shows an autosomal recessive pattern of inheritance. It has been linked to mutations in the SBF1 gene, a predicted pseudophosphatase gene.