He Was Unbearably Itchy, but the Problem Wasnt in His Skin – The New York Times

When the patient was dressed, Iammatteo returned to the examination room. She didnt 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 wasnt until a diagnostic blood test was developed that other manifestations of the disease were identified. In whats 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.

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 couldnt 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 couldnt 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.

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 couldnt? the patient asked when he saw her for a follow-up visit. She explained that shed 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 shes not so sure. Since making this patients 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 Ive been successfully diagnosing more of it because its on my mind.

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He Was Unbearably Itchy, but the Problem Wasnt in His Skin - The New York Times