Erica was hugely frustrated. “I’ve had the council round several times, they’ve fumigated the whole place twice, and still I’m getting bitten.” I peered at her lower legs. There were scattered red lumps and lots of scratch marks. The pest control officer, having exhausted his insecticidal repertoire, had sent Erica along to me.
The commonest reason for someone being eaten alive in their own home is the death of a cat. Fleas live in carpets, hopping on to the resident pet when in need of food. As long as Tiddles remains hale and hearty, human beings are bitten only sporadically. But a few weeks after a feline departure, the now-starving fleas start to feast on the grieving owner. Erica, however, denied any previous pet ownership. And flea bites are typically clustered around the ankles and lower shins, whereas Erica said she was affected all over.
I scrutinised the skin of her wrist and the web spaces between her fingers. Infestation with scabies is surprisingly common, and those areas are favourite locations for the mites. There was nothing to see, though. And while most of her torso was scratched and bump-strewn, her mid-back was blemish-free. This pattern suggests something called prurigo. Incessant scratching of normal skin results in raised red prurigo lumps, which can easily be mistaken for insect bites. The area between the shoulder blades remains unaffected, though, because it is impossible to scratch there concertedly.
Numerous conditions can cause generalised itching, from iron deficiency to an underactive thyroid. I took blood samples and gave Erica a prescription for a bottle of Eurax – a fantastic lotion that will suppress itching, whatever the cause. A week later the blood tests were back, and normal. Erica was back, too. And this time she’d brought specimens of the offending insects to show me. “There!” she announced, handing me a little glass jar. Inside were a couple of wisps of dark fluff and some indeterminate bits of debris. Not even tapping the contents on to my palm for a sift-through could produce any evidence of life forms.
Something about the little glass jar rang a bell. The “matchbox sign” describes the tendency of a particular sort of patient to bring spurious evidence in a small container to show the doctor. I looked at Erica afresh: in her late fifties, a trifle eccentric, but absolutely no history or indication of any mental or physical illness. I wondered if she might have Ekbom syndrome, or delusional parasitosis.
Delusional parasitosis is a belief that one is infested with some sort of parasite. In all other respects the patient is functioning normally, and so presents a convincing account of his or her troubles to pest control personnel, doctors and veterinarians. A big problem with Ekbom’s is the characteristic refusal of the sufferer to accept that he or she is suffering from a mental illness. Antipsychotic drugs, more often used for treating schizophrenia, can be very effective, but most patients reject them out of hand.
“I’d like you to try these tablets,” I told Erica. “They’re usually used to treat schizophrenia, but bizarrely enough they’re also quite likely to reduce the itch and the rash you’re experiencing.” I smiled, hoping she wouldn’t probe my explanation. I wasn’t lying as such; just being careful which bits of the picture I painted.
She returned to the surgery a month later and, to my relief, had taken the tablets. “It’s amazing,” she told me, “it’s completely better.” She showed me a few areas of pristine skin, and then she fell silent for a few moments. When she spoke again her voice was lowered, embarrassed. “Doctor, was I psychotic?”
“Well, yes,” I told her, and explained about Ekbom syndrome. With recovery had come full insight, and she recounted, with something akin to awe, how she now looked at the specimens she’d collected and could see that they were nothing but fluff, but could clearly remember perceiving them as dead insects. And the persistent sensation of things crawling over her skin had been utterly real to her.
Ekbom’s is fascinating and rare; I doubt I’ll see another case. Pest control officers probably encounter it more often. I imagine they have a cut-off – perhaps two failed fumigations, or when the homeowner starts to present them with bits of debris in a matchbox – when they suggest that a doctor might be better placed to help with this particular infestation.