Assistant Professor University of Ottawa Ottawa, Ontario, Canada
Case Diagnosis: Hereditary Neuropathy with liability to Pressure Palsies (HNPP) with atypical presenting symptoms.
Case Description: An 18-year-old woman was referred to Electromyography Clinic with a two-year history of episodic erythematous skin discoloration and paresthesia affecting the feet, hands, and nose. Episodes were triggered with standing or walking for 5-10 minutes. Physical exam revealed pes cavus, impaired pinprick sensation in the feet to mid-shin, and generalized absent or hypoactive reflexes. There were no gait, balance, or hand dexterity impairments. Muscle bulk and strength were normal. Family history was notable for high-arched feet in her mother and brother, but no known polyneuropathy or mobility impairments. The patient was training to become a hair stylist. Nerve conduction studies demonstrated a mild sensorimotor polyneuropathy and focal ulnar mononeuropathies at the elbows. Given the electrodiagnostic findings, physical exam, and family history suspicious for a hereditary polyneuropathy, genetic testing for inherited polyneuropathies was ordered. Results confirmed a PMP22 deletion, establishing a diagnosis of HNPP.
Discussions: To our knowledge, this is the first report of HNPP presenting with positional or exercise-induced erythromelalgia as the primary symptom. Although HNPP is classically considered a large-fiber neuropathy, autonomic and small-fiber involvement has been reported. Damage to autonomic fibers can result in vasomotor dysregulation, which we speculate may manifest as erythromelalgia in this case. Small-fiber dysfunction may occur despite mild abnormalities on nerve conduction studies, allowing autonomic syndromes to predominate the clinical presentation. The diagnosis in this case may have important implications for the patient’s chosen field of work and a strong emphasis on education and counselling was placed to minimize progression of mononeuropathies.
Conclusions: Clinicians may consider HNPP in the differential diagnosis of patients presenting with erythromelalgia and signs of polyneuropathy. Further studies are needed to clarify underlying mechanisms of erythromelalgia presenting in someone with HNPP, its prevalence, and clinical significance it may represent.
