Hereditary neuropathy with liability to pressure palsies (HNPP)
Incidence
AR inheritance. A DNA Deletion in Hereditary Neuropathy with Liability to Pressure Palsies seems to be the cause of the condition.
Clinical Characteristics
Hereditary neuropathy with liability to pressure palsies (HNPP), also termed "familial recurrent polyneuropathy" or "tomaculous neuropathy," has been considered a distinct entity from CMT on the basis of different clinical presentation and of a different histopathological and electrophysiological pattern. The clinical features of HNPP, usually appearing during adolescence, are recurrent attacks of numbness, muscular weakness, and atrophy. In some cases, these are associated with palsies triggered by compression or trauma. Segmental demyelination and thickenings of the myelin sheath (tomaculous or "sausage-like" structures) are typical pathological findings in HNPP. Patients with HNPP frequently have carpal tunnel syndrome and other entrapment neuropathies. Electrophysiology is usually normal; therefore it is not helpful in HNPP, but it may reveal a reduction of nerve-conduction velocity or a conduction block in a few cases. A DNA Deletion in Hereditary Neuropathy with Liability to Pressure Palsies seems to be the cause of the condition. The deletion measured approximately 1.5 Mb and included all the markers that were found to be duplicated in CMT1A in chromosome 17. FISH is probably the best method to detect the HNPP deletion.
Precipitants
The condition present recurrent attacks of numbness, muscular weakness, and atrophy. In some cases, these are associated with palsies triggered by compression or trauma.
Provocation Tests
no
Diagnostic Procedures
Electrophysiology is usually normal; therefore it is not helpful in HNPP, but it may reveal a reduction of nerve-conduction velocity or a conduction block in a few cases. FISH is probably the best method to detect the HNPP deletion.