Recurrent Pulmonary Nodules, from Pulmonary Cryptococcosis to ANCAAssociated Vasculitis: A Case Report

On chest Computed Tomography (CT), pulmonary cryptococcosis and antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) can both present as multiple non-cavitating pulmonary nodules. As a result, when such nodules worsen during antifungal therapy in a patient with pulmonary cryptococcosis, it is difficult to determine whether this represents progression of the infection or the development of concomitant AAV, posing a significant diagnostic challenge.

A 67-year-old man presented with multiple non-cavitating pulmonary nodules and was diagnosed with pulmonary cryptococcosis. He completed a full course of antifungal therapy with clinical and radiologic improvement, and treatment was discontinued. After stopping therapy, he relapsed with the same pattern of multiple non-cavitating pulmonary nodules. Restarting antifungal therapy led to regression of the lesions. Unexpectedly, during antifungal maintenance therapy, he again developed multiple non-cavitating pulmonary nodules. Laboratory testing showed positivity for myeloperoxidase (MPO) and perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA), supporting a diagnosis of microscopic polyangiitis (MPA), a subtype of AAV. After discontinuation of antifungal therapy and treatment with prednisone plus mycophenolate mofetil, the pulmonary nodules showed marked regression.

Multiple non-cavitating pulmonary nodules can be an atypical presentation of MPA and overlap radiologically with pulmonary cryptococcosis. Accurate differentiation should integrate ANCA serology with careful assessment for involvement of other organ systems.