“I feel like my body has been taken over by aliens!” the thin 82-year-old man exclaimed. Dr. Melissa Iammatteo, the chief of allergy and immunology at Westmed Medical Group in Purchase, N.Y., nodded sympathetically. This was her first appointment with the older man, who had come to discuss the itchy rash that had made his life unbearable. At his age, he told the doctor, he’d been through a lot — heart disease, chronic kidney disease, gout — but “this was a whole new ballgame.”
For the past several years, he told the doctor, he’d had sensitive skin, thin with age and easily injured. But about six months earlier, he began to itch like crazy. It started with a rash. Big red blotches suddenly appeared on his chest, belly, backside and thighs. Right from Day 1, they were unbelievably itchy. He couldn’t sleep, could barely read or think. He went to see one dermatologist after another. They’d taken biopsies and sent him for blood work. He was treated with steroid creams — first strong, then stronger. They didn’t help. Then UV-light therapy; after 20 treatments, he gave up on that too.
The last dermatologist thought he might have scabies — tiny mites barely visible to the naked eye that can live on the body and cause intense itching, or pruritus. But despite two courses of a total-body insecticide cream, the man was still scratching himself raw.
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Perhaps an Allergy
The last dermatologist he saw began to suspect that perhaps it was a skin manifestation of a disease somewhere else in the body. Two biopsies showed the presence of eosinophils in his skin. Eos, as they are known more familiarly, are a type of white blood cell that can be seen in eczema or other allergic reactions. This rash clearly wasn’t eczema — none of the usually effective treatments for eczema had worked. The itch of scabies is also an allergic reaction, but getting rid of the mites ends the itch, so it wasn’t scabies. He was probably allergic to something, but it wasn’t clear what. She sent the patient to Iammatteo, an allergy specialist. Iammatteo was well known for her extraordinary ability to figure out tough cases — even when they weren’t caused by allergies.
The night before her appointment with the itchy man, Iammatteo pored over the patient’s medical records, as was her practice, to try to get a sense of what might be going on. In reviewing the man’s chart, she noticed that in addition to eos in his skin, the patient had an overabundance of eos in his blood — more than three times the number normally seen in circulating blood. Allergies didn’t cause those kinds of numbers. What, then, could cause that kind of cell to proliferate?
Generally, the No. 1 job of eos in the body is to fight off parasites. In the United States, one of the most common parasites is toxocara, which is transmitted from the feces of infected dogs and cats. Strongyloides, another parasite, has been found in people who have spent time in tropical or subtropical regions where it is endemic. Both can cause a rash like this, so either was possible. More concerning in a patient at this age was a malignancy or a syndrome of hypereosinophilia — a disorder in which this type of white blood cell begins to proliferate wildly.
Beware Dogs and Cats
She saw the man early the next day. He was chatty, but even as he told his story, he could not stop scratching. It turned out that he had had a cat that was old and sick, and his half brother had two dogs and four cats that he’d recently spent time with. So toxocariasis certainly was possible. He had visited the Caribbean many times — though not recently. Still, that meant strongyloidiasis was also a potential culprit. Besides the itch and the sleep deprivation it caused, he had no other complaints.
On examination, the man’s body was covered with well-defined red inflamed patches on his chest, back, buttocks and thighs that were crisscrossed with scratch marks. In some areas the skin was thick, leathery and lumpy from the rash and the skin’s response to persistent scratching or rubbing. Other areas were covered with tiny flakes of scaling skin.
When the patient was dressed, Iammatteo returned to the examination room. She didn’t think this was an allergy, she told him. But it could be a parasite. She thought it was more likely toxocara, given his recent exposures to dogs and cats. Toxocara is a type of parasite called a nematode or roundworm. It lives in the gastrointestinal tract of dogs and cats. Until the end of the 20th century, visceral toxocariasis could be diagnosed only by the symptoms it caused when it invaded the organs of the body — the liver, the lungs, the brain or the eyes. These were serious infections — causing everything from wheezing and shortness of breath to blindness or, rarely, death. It wasn’t until a diagnostic blood test was developed that other manifestations of the disease were identified. In what’s called common toxocariasis, patients have gastrointestinal symptoms as well as an itchy rash. In covert toxocariasis, the only symptom is an itchy rash. These infections often resolve on their own over time, but they can also be treated with a medicine. This patient could have covert toxocariasis.
Narrowing Things Down
Iammatteo said she would test for both toxocariasis and strongyloidiasis. She would also refer him to a hematologist to look for a malignancy or other trigger that might have caused his overproliferation of white blood cells. There were other causes of his rash and eosinophilia, but these were the most likely and a good place to start.
A few days later, she got a possible answer and called the patient. You probably have toxocariasis, she told him. The blood test came back positive, but she explained there was a caveat. The test measures whether the immune system has responded to this particular parasite — ever. The fact that it was positive meant that the patient had been exposed to the parasite, but it couldn’t determine when the exposure occurred. Toxocara infections are most common in children. But the test will still be positive even if the infection is long gone. The only way to know for certain that the toxocara was causing the itch, she told him, was to treat him and see how he responded. She referred him to an infectious-disease doctor who prescribed the recommended five days of Albendazole.
Because he couldn’t know for sure if this was the right diagnosis, the patient kept his appointment with the hematologist. That doctor sent off more blood to look for signs that the overabundance of these cells could be caused by an eosinophil gone wild.
Relief at Last
But well before those tests results came back negative, the patient felt that he had his answer. Within days of completing his treatment with Albendazole, the itching resolved. And by the time he went back to see Iammatteo two weeks later, even the rash had mostly disappeared.
Why had Iammatteo been able to figure this out when other doctors couldn’t? the patient asked when he saw her for a follow-up visit. She explained that she’d gone to Albert Einstein College of Medicine in the Bronx, and one professor there was an expert in parasitology. She took her class, and what she learned stuck with her. Different medical schools have different strengths, she told me later. Parasites were one of theirs.
And, she added, doctors are taught that toxocara infection is rare. But now she’s not so sure. Since making this patient’s diagnosis last spring, she told me she has diagnosed nearly a dozen cases of toxocariasis in patients whom she might not have thought to test for the parasite if not for this older man and his rash. “I know I’ve been successfully diagnosing more of it because it’s on my mind.”
