Hereditary Motor and Sensory Neuropathy: PMP22 Duplication / Deletion Analysis

Diagnostic Use

The hereditary motor and sensory neuropathies (HMSN) are a heterogeneous group of peripheral neuropathies with a combined incidence of 30:100,000. Charcot-Marie-Tooth Type 1, CMT1 is the most common clinical form of HMSN with an incidence of 15:100,000. It is usually inherited as an autosomal dominant condition and is characterised by slowly progressive distal limb muscle weakness and atrophy affecting the peroneal muscles. Onset is typically in the first or second decade of life although considerable variation in clinical presentation is observed. Life expectancy is not changed.
The most common subtype of CMT1 is called CMT1A, caused by duplication of the PMP22 gene on chromosome 17p11.2. In approximately one third of cases, duplication occurs de novo. CMT1A comprises approximately 70% of CMT1.
The genetically related condition “Hereditary Neuropathy with liability to Pressure Palsies” (HNPP) is an inherited recurrent focal neuropathy, characterised by painless nerve palsies following mild pressure or trauma. Peripheral nerve biopsy reveals sausage-shaped thickenings on the myelin sheath termed tomaculae. Therefore this condition is also known as Tomaculous Neuropathy. HNPP varies in severity and age of onset, and often remains undiagnosed. In all reported cases, it occurs as a result of deletion of the PMP22 gene.


Genetics - Molecular Pathology

Delphic Registration Code


Constituent Tests


Charcot-Marie-Tooth Disease
Tomaculous Neuropathy

Turnaround Time

4 hours

Test Code