Hereditary Neuropathy With Liability to Pressure Palsy Detected During the Use of Recreational Drugs.

Background: Nitrous oxide (N₂O) has been an increasingly popular recreational drug over the past few years. Abuse is associated with severe neurological complications and even fatal outcomes. Purpose: Here we present a case of chronic nitric oxide abuse in a teenager presenting with rapidly progressive mixed sensory and motor polyneuropathy. Results: The initial diagnostic workup excluded electrolyte derangement, heavy metal intoxication, autoimmune neuropathy, myopathy, hematological disorders, and thyroid disease. On further questioning, patient reported 8-months of inhalation of nitrous oxide, commonly known as "whippets". Subsequent tests revealed low Vitamin B12 and elevated homocysteine level. Eventual genetic test demonstrated a heterozygous deletion in the gene that encodes the peripheral myelin protein 22 (PMP22), consistent with a diagnosis of Hereditary Neuropathy with Liability to Pressure Palsies (HNPP). Conclusion: The association of neurologic and genetic findings with the timeline of nitrous oxide inhalation suggests a multifactorial etiology of her symptoms, with the N₂O acting as a trigger to the axonal degeneration and demyelination detected on electrodiagnostic studies.