A case of familial episodic pain syndrome with SCN11A mutation treated prophylactically with sodium channel blockers

Familial episodic pain disorder is a rare autosomal-dominant disorder characterized by recurrent attacks of pain. A gain-of-function mutation in SCN11A has been identified in this rare, early-onset familial episodic pain disorder. Currently available treatment options are warmth, massage, and administration of analgesics. Here, we report a patient with familial episodic pain disorder who received prophylactic treatment. A 4-year old Japanese girl presented with a history of intense episodic pain in the distal extremities and knees since infancy. Pain attacks were sometimes triggered by low ambient temperatures or fatigue, although the trigger for the majority of attacks could not be identified. She experienced frequent episodes of pain (5 or 6 attacks per day) with each attack lasting 30-60 min. Each attack persisted for 2 or 3 days and occurred every week. The pain was intense and unbearable, occurring late in the day or at night. The patient sometimes awoke from sleep because of the pain. There was no change in skin color, nor did she experience sweating during pain attacks. Her 32-year-old father has been experiencing the same symptoms since childhood. Investigation of the family history revealed many affected individuals with the autosomal-dominant trait. The severity of pain in the affected family members decreased with age. The patient's father continues to take analgesics ones or twice a month. An SCN11A mutation, NM-014139.2: c. 665 G>A(p.Arg222His), was identified in the family. Acetaminophen was effective, but the patient required frequent administration; therefore, we considered prophylactic treatment. Carbamazepine and gabapentin did not yield adequate relief. Subsequently, we administered lamotrigine, which was reportedly effective in a previous case of the p. Arg222His mutation. However, lamotrigine was ineffective for our patient. Currently, no prophylactic treatment has been identified that consistently prevents pain attacks in familial episodic pain disorder.