The clinical and electrodiagnostic features of 10 adults in a family with axonal, autosomal dominant, hereditary motor and sensory neuropathy (HMSN IIB), with linkage to chromosome 3q, are reported from Washington University School of Medicine, St Louis, MO. Symptomatic age at onset is in the second or early third decade; 7 of 10 subjects noted foot drop or weakness while in high school. Some complained of diminished sensation in the feet and toe/foot ulcerations. Intrinsic hand muscles were mildly affected in younger, and wrist and finger extensors in older patients. All had pes cavus or hammer toes. Ankle reflexes were reduced. Electrodiagnostic studies showed a distal sensorimotor axonopathy with normal motor conduction velocities. The disorder was thought to be a distinct subtype of HMSN II. 
COMMENT. Autosomal dominant hereditary motor and sensory neuropathies (HMSNs) are either predominantly demyelinating in type (HMSN I), with slowed conduction velocities and hypertrophic nerves, or axonal (HMSN II), with normal conduction velocities, small compound muscle action potentials, and axonal degeneration. The above report of HMSN IIB appears to be a homogeneous entity, exhibiting linkage to chromosome 3q, younger age at onset, and characteristic clinical and electrodiagnostic features.
A novel point mutation in the peripheral myelin protein 22 (PMP22) gene is reported in association with HMSN I (Charcot-Marie-Tooth type 1A) from the University of Cagliari, Italy . PMP22 protein maintains normal function of peripheral nerve myelin, and the location of the mutation determines the phenotype of HMSN I disease.