Granulomatosis with polyangiitis and neuroendocrine intestinal tumor: a unique and challenging combination in a case report

We report the case of a 43-year-old male smoker who presented to the emergency department with skin lesions resembling pyoderma on the lower extremities, punctate and necrotic digital ulcers, fever, malaise, polyarthralgia and elevated inflammatory markers. He later developed bilateral, asymptomatic cavitary pulmonary nodules, diffuse alveolar hemorrhage, pansinusitis, and positive PR3-ANCA, establishing the diagnosis of GPA. An excellent initial response was observed with pulse methylprednisolone, oral prednisolone, intravenous pulse cyclophosphamide, and hyperbaric oxygen therapy (HOT).

Three months later, however, he was diagnosed with a NET of the small intestine. It was polypoid and multifocal, with high catecholamine production but low Ki-67, leading to a reduction in immunosuppressive therapy. Two new flares occurred, with skin, renal, ocular, intestinal, and joint involvement, along with elevated c-ANCA levels, prompting a reinduction strategy with rituximab, plasmapheresis, corticosteroids, and HOT, resulting in significant improvement.

In addition to the complex and challenging clinical management of this case, this unique combination – GPA and NET – is highlighted.