ICD-9-CM 343 | ||
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GeneReviews Hereditary Neuropathy with Liability to Pressure Palsies | ||
Hereditary Neuropathy with Liability to Pressure Palsy (HNPP) is a peripheral neuropathy, a disorder of the nerves. HNPP is a nerve disorder that affects the peripheral nerves,—pressure on the nerves can cause tingling sensations, numbness, pain, weakness, muscle atrophy, and even paralyzation of affected area. In normal individuals these symptoms disappear quickly but in sufferers of HNPP even a short period of pressure can cause the symptoms to occur. Palsies can last from minutes, days to weeks, or even months.
Contents
The symptoms may vary—some individuals report minor problems, whilst others experience severe discomfort and disability. In many cases the symptoms are mild enough to go unnoticed. The time period between episodes is known to vary between individuals. HNPP has not been found to alter the lifespan, although in some cases a decline in quality of life is noticed. Some sufferers (10-15%) report various pains growing in severity with progression of the disease. The nerves most commonly affected are the peroneal nerve at the fibular head (leg and feet), the ulnar nerve at the elbow (arm), and the median nerve at the wrist (palm, thumbs and fingers), but any peripheral nerve can be affected. HNPP is part of the group of hereditary motor and sensory neuropathy (HMSN) disorders and is linked to Charcot–Marie–Tooth disease (CMT).
Symptoms/signs
Among the signs/symptoms of hereditary neuropathy with liability to pressure palsy are the following (different symptoms are caused by different nerves, such as the foot drop is caused by the peroneal nerve):
Causes
Hereditary neuropathy with liability to pressure palsy is an autosomal dominant genetic disease (which means one parent must be affected). A mutation in one copy of the gene PMP-22 (Peripheral myelin protein 22, 17p11.2) that makes the peripheral myelin protein causes haploinsufficiency, where the activity of the normal gene is insufficient to compensate for the loss of function of the other gene.
Molecular biology/genetics
Peripheral Myelin Protein 22 gene entails about 5% of the PNS myelin, it is located on chromosome locus 17p12
Overlap with Charcot-Marie-Tooth disease type 1A has been found in Gly94fsX222 (c.281_282insG), due to point mutations of PMP 22 that occur in a minority of cases of hereditary neuropathy with liability to pressure palsy. The point mutations -missense, nonsense and splice-site have each been alluded to in HNPP.
Diagnosis
In terms of diagnosis of HNPP measuring nerve conduction velocity may give an indication of the presence of the disease.Other methods via which to ascertain the diagnosis of hereditary neuropathy with liability to pressure palsy are:
Treatment
There is no current treatment, however management of hereditary neuropathy with liability to pressure palsy can be done via:
History
Inherited PNS disorders were first described by Charcot, Marie and Tooth (1886). De Jong (1947) first described HNPP in a Dutch family. Dyck and Lambert (1968) showed nerve conduction studies, and Chance et al. (1993) detected the chromosome deletion in most of the individuals with the HNPP condition.