Yield of the PMP22 deletion analysis in patients with compression neuropathies.

Hereditary neuropathy with liability to pressure palsies (HNPP) is a rare neuromuscular disorder, mostly caused by PMP22 deletion. To determine a yield of the genetic analysis of PMP22 gene deletion in patients with compression neuropathies. We included 112 patients with clinical suspicion of HNPP diagnosis. Nerve conduction studies (NCS) were performed for motor and sensory nerves bilaterally. Number of the PMP22 gene copies was determined using a real-time polymerase chain reaction (RT-PCR). PMP22 deletion was found in 34 (30.3%) patients. Patients with genetically confirmed HNPP had 12 years earlier disease onset compared to other patients with compression neuropathies (p < 0.01), more nerves affected during lifespan (5.5 ± 3.5 vs. 3.0 ± 2.0, p < 0.01) and at the time of referral (2.7 ± 2.5 vs. 2.0 ± 1.9, p < 0.05). HNPP patients had positive family history more frequently (p < 0.01). Foot deformities (pes cavus and hammertoe), symmetric muscle atrophy in lower legs and absent muscle reflexes in lower limbs were more common in HNPP patients. NCS abnormalities were also more common in HNPP group. Multiple linear regression analysis identified positive family history (β =  + 0.35, p < 0.01) and decreased sensory conduction velocity in at least three sensory nerves (β =  + 0.40, p < 0.01) as independent predictors of the PMP22 deletion. Among patients with compression neuropathies, those with a positive family history, earlier symptom onset and NCS abnormalities had a higher chance to have PMP22 deletion.