The condition generally known as familial rectal pain syndrome is a rare autosomal dominant disorder that was first described by Hayden and Grossman.¹ The term familial rectal pain, was coined by Dugan.² The OMIM database (http://www.ncbi.nlm.nih.gov/entrezdispomim.cgi?id=167400) uses the term “pain, submandibular, ocular and rectal, with flushing”.

The disorder starts in the neonatal period (possibly in utero) and is lifelong. Its most characteristic clinical features are attacks of excruciating pain that affect various parts of the body, including the rectum, genitalia, face and limbs. In addition, other features reflecting autonomic dysfunction occur, including harlequin colour changes and pupillary abnormalities. Some patients with the disorder experience non-epileptic tonic seizures during severe episodes of pain. These may be associated with cardiac asystole.

Over the past decade, a worldwide consortium of clinicians, geneticists and scientists have been attempting to find the cause of familial rectal pain and recently discovered that it is caused by mutations in the sodium channel SCN9A.³ The consortium has worked …