Oral Iron Therapy for Iron Deficiency Anemia Harmful and Cold-Water Emersion Helpful for Episodic Pain in A Patient with NaV1.7 Sodium Channel Gene SCN9A Hyperactive A1632E Mutation

Abstract

The first patient described with both paroxysmal episodic pain disorder and erythromelalgia secondary to a unique A1632E mutation of the SCN9A gene demonstrated early breath-holding spells and bradycardia requiring a pacemaker. Frequent episodes of pain were helped by routine oxcarbazepine-carbamazepine therapy from an early age. Additional relief was found when she was older and could jump into the family swimming pool or take a quick cold shower to lower pain intensity. Puberty was delayed. After it started, she became moderately anemic after excess menstrual blood loss over 2 years. Episodes of intermittent pain became more severe, particularly during menstrual periods. Frequent lower leg muscle pains developed as her anemia worsened. Oral iron therapy for iron deficiency anemia led to more intense muscle pains, particularly in her legs, and intense abdominal pain. The adverse reaction was attributed to ingested iron, with positive iron Fe⁺³ group binding to her de novo appearing mutant glutamic acid A1632E with negative carboxyl CO₃^- that was not a part of the normal SCN9A gene sequence. A unit of packed red cells, followed by another 3 months later, a vegetable based iron preparation, and an iron patch successfully treated her anemia and her symptoms improved