When the pain comes, Alina Delp retreats to air conditioning as soon as possible. What begins to feel like a mild sunburn will, if left unattended, turn into a raging, burning pain.
"It's this turbulent, violent sensation that feels electric and stinging," Delp says, describing the pain at its worst. "I've run out of the building screaming like a lunatic before because it's been so bad."
Delp has erythromelalgia, a rare condition in which a person's body (typically the feet and the hands, though Delp experiences pain all over) reacts to mild warmth as though it is on fire. Mild exertion, even just standing, will set it off for Delp, which meant quitting her job of 15 years as a flight attendant. Two years of countless doctors' appointments finally got her a diagnosis in 2012, but current medications are unable to relieve pain in most patients.
"I'm pretty much a prisoner in my own home," she says. Her house in Tacoma, Washington, is kept at a chilly 58 degrees Fahrenheit, thanks to some special duct work that her husband, coincidentally in the heating and cooling business, was able to arrange. Delp spends most of her time reading, watching TV, or working on her computer to maintain an online erythromelalgia support group that she co-founded.
But, this horrific condition has handed pain researchers their most promising drug target in years. In 2004, a study of an inherited version of erythromelalgia pinpointed a mutation in a gene that directs the making of a sodium channel, called Nav1.7; sodium channels are proteins that help control the electrical excitability of neurons.
"The channel sets the sensitivity of pain-signaling neurons, and when you have those Nav1.7 mutations, the neurons fire when they shouldn't," says Stephen Waxman of Yale University School of Medicine, New Haven, US, and the Veterans Affairs Medical Center, West Haven, Connecticut. Waxman was the first to study the effects of Nav1.7 mutations in neurons.
Delp doesn't know if she has this type of mutation, but medicines that calm the channel may still give her relief. Multiple clinical trials are underway to test Nav1.7 channel blockers, not only in inherited erythromelalgia, but in more common conditions, like sciatica and trigeminal neuralgia, which both involve intense shooting pain in different parts of the body.