Dejerine-Sottas disease
Dejerine-Sottas disease is a slowly progressive, autosomal-recessive disorder that begins in early childhood, manifested by delay in developmental milestones, such as the acquisition of motor skills.
In contrast to HMSN I and HMSN II, in which muscular atrophy is limited to the leg, both trunk and limb muscles are involved in Dejerine-Sottas disease.
On physical examination, enlarged peripheral nerves can be detected by inspection and palpation. The deep tendon reflexes are depressed or absent, and nerve conduction velocity is slowed.
HMSN III is genetically heterogeneous, and arises from distinct mutations in the same myelin-associated genes that are mutated in HMSN I. These include genes encoding peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ), periaxin (PRX), and early growth response 2 (EGR2).
Morphologically, the size of individual peripheral nerve fascicles is increased, often dramatically, with abundant onion bulb formation as well as segmental demyelination. There is usually evidence of axonal loss, and the axons that remain are often of diminished caliber. These findings are most severe in the distal portions of the peripheral nervous system; however, autopsy studies have shown that similar findings may be present in spinal roots.