Say you were a doctor with experience in treating bronchiectasis. You have been practicing medicine for many years and have seen a wide variety of patients with varying degrees of symptoms. One day, a 71-year-old man walks into your clinic with a painful, swollen rash on his right foot. He has had the rash for one day and bronchiectasis for at least six years. What would you do?

As described by a case study report, “Painful Rash in a Patient with Bronchiectasis,” published in JAMA Clinical Challenge, you have at least four options. Quite simply, you could prescribe the patient a high-potency topical steroid. Alternatively, you could obtain blood cultures and empirically treat the patient with the antibiotic vancomycin. Similarly, you could also perform a herpes simplex virus/varicella zoster virus direct fluorescent antibody test and empirically treat the patient with the antiviral drug valacyclovir. Finally, you could obtain antineutrophilic cytoplasmic antibody (ANCA) titers to test for causes of inflammation.

Before making this decision, you conduct a standard clinical evaluation to physically examine the patient and obtain a leukocyte count. Based on your findings, you diagnose the patient with eosinophilic granulomatosis with polyangiitis (EGPA), previously known as Churg-Strauss syndrome, because the patient had a leukocyte count of 15,700 cells per microliter, and 38% (5,950 cells per microliter) of those were eosinophils. The normal range of eosinophils is less than 350 cells per microliter.

Now that you have a diagnosis, the choice is clear: you should obtain ANCA titers. These tests will help evaluate other underlying diseases. “ANCA-positive patients are more likely to have renal involvement and peripheral neuropathy; ANCA-negative patients more commonly have cardiac disease,” explained Sruthi Renati, lead author of the study at Beth Israel Deaconess Medical Center in Boston.

As it turns out, the patient has positive ANCA titers. Further evaluation shows the patient also had abnormal red blood cells and requires treatment with oral prednisone and cyclophophamide. This treatment ends up helping your patient’s rash and bronchiectasis. “Within 3 days both his painful rash and pulmonary symptoms substantially improved,” wrote Renati. “He continues to do well as the prednisone dose is slowly tapered down.”

For you, treating bronchiectasis patients such as these is all in a day’s work.