Symptoms of Hereditary Neuropathy with Liability to Pressure Palsies (HNPP)
HNPP typically presents with recurrent, painless episodes of focal motor and sensory peripheral mononeuropathy, usually triggered by minor trauma or compression at entrapment sites. 1
Primary Clinical Manifestations
- Episodic symptoms: Recurrent episodes of transient focal weakness or sensory loss, typically related to activities causing nerve compression, stretching, or minor repetitive trauma 2
- Common sites: Predominantly affects nerves at entrapment points around the wrists, knees, elbows, and shoulders 3
- Sensory symptoms: Paresthesias (tingling, burning sensations), numbness in affected nerve distributions 1, 4
- Motor symptoms: Muscle weakness and possible atrophy in affected areas 1
- Common presentations: Peroneal palsies (foot drop), carpal tunnel syndrome, and other entrapment neuropathies 1, 5
Characteristic Features
- Pain profile: Episodes are typically painless, distinguishing HNPP from some other neuropathies 1, 3
- Age of onset: Generally develops during adolescence, though can present in childhood 1, 4
- Recovery pattern: Patients typically make full recovery after each episode, though recurrent episodes may cause residual deficits 4
- Trigger factors: Episodes often precipitated by:
Less Common Presentations
- Multiple simultaneous neuropathies: Some patients may present with multiple compression neuropathies simultaneously, such as bilateral hand numbness 5
- School performance issues: In children, fluctuating distal paresthesias may disrupt learning 4
- Activity-specific symptoms: Cramps related to specific activities (e.g., piano practice) 4
- Subtle manifestations: Some patients may have discrete muscle weakness with no functional complaints 4
Diagnostic Considerations
- Electrophysiological findings: Motor and sensory nerve conduction velocities are typically reduced in clinically affected patients and even in asymptomatic gene carriers 1
- Histopathological changes: Peripheral nerves show segmental demyelination and characteristic "sausage-like" formations (tomacula) 1
- Genetic basis: Most frequently associated with a 1.4-Mb deletion on chromosome 17p12 affecting the PMP22 gene 1, 3
- Differential diagnosis: May be misdiagnosed as Charcot-Marie-Tooth disease type 1 due to some overlapping features 1, 3
Clinical Course
- Asymptomatic periods: The condition may be completely asymptomatic until triggered by an event 3
- Underdiagnosis: Particularly in childhood, HNPP is likely underdiagnosed due to its wide spectrum of clinical presentations 4
- Family history: Often reveals other affected family members with undiagnosed HNPP 4
- Long-term prognosis: While individual episodes typically resolve completely, recurrent episodes may lead to permanent neurological dysfunction 2
Understanding these symptoms is crucial for early diagnosis and management to prevent recurrent episodes through patient education about avoiding prolonged nerve compression.