HNPP

Hereditary neuropathy with liability to pressure palsies (HNPP) is  a genetic disease consistent with autosomal inheritance. PMP 22 gene mutation is the fundamental mechanism; consistent with frameshift mutation.  PMP 22 gene’s product is a peripheral myelin protein responsible of peripheral nerves’ endurance and resistance.  Charchot Marie Tooth Disease Type 1A (CMT1A ) and CMT1E also  share same gene deletion mechanism  located in  17p 11.2  choromosome.  

HNPP is characterized by  acute onset  of repeated  painless focal sensory and motor entrapment neuropathies such as carpal tunnel syndrome and peroneal palsy with foot drop. Some patients presents with transient sensory phenomena without weakness. The first  attack usually occurs in the second or third decade, although the age range extends from two to 70 years. %80 of cases are inherited while %20 are de-novo. Certain diagnosis is avaliable with genetic test. This autosomal dominant disease could be considered in progressive and repeating neuropathies in young patients without systematic disease; even without frank family history

The exact prevalance of HNPP is unknown due to under diagnosis but estimated to be 2-5/100,000. Five phenotype is described in literature as; Recurrent positional short-term sensory symptoms, Progressive mononeuropathy , CMT-like polyneuropathy,  Chronic sensory polyneuropathy and CIDP like disease. Avoiding long term pressure on joints are the fundamental management.  Corticosteroids has no benefical effects despite one case record in literature. Sudden  weight loss or weight gain such as pregnancy can sum up wiht exabarations in general condition. One HNPP case was described as a predisposing factor for CIDP after influenza AH1N1 vaccination. 

Share this