Case Presentation: A 65 year-old Mexican man had presented to an outside hospital with 2 weeks of cough and dyspnea and was found to have a new apical pulmonary infiltrate. He underwent lung biopsy and was treated for pneumonia for several days without resolution of his symptoms. He was transferred to our medicine service and on presentation he was febrile, tachycardic, and hypoxemic. Laboratory results revealed a leukocytosis, elevated serum creatinine, proteinuria, and hematuria. He quickly developed oliguria requiring continuous renal replacement therapy, hemoptysis, and respiratory failure requiring intubation. Chest computed tomography (CT) showed a large apical mass and worsening bilateral infiltrates. Sputum was positive for acid-fast bacilli (AFB) but Mycobacterium tuberculosis (MTB) polymerase chain reaction (PCR) was negative. Treatment for active MTB infection was started but there was also a growing concern for alveolar hemorrhage. Bronchoalveolar lavage was negative for bacteria, fungi, or malignancy. Anti-glomerular basement antibody was negative. Anti-proteinase 3 antibody was markedly elevated. Prior lung biopsy showed non-specific inflammation. Renal biopsy revealed pauci-immune necrotizing vasculitis consistent with granulomatosis with polyangiitis (GPA). Treatment with steroids, plasma exchange, and rituximab was started. MTB treatment was discontinued when culture demonstrated non-MTB Mycobacterium. After discharge the patient’s symptoms improved on a steroid taper. His lung mass completely resolved and he no longer required dialysis.

Discussion: Pulmonary MTB infection, malignancy, and GPA can present with hemoptysis and respiratory distress. Differentiating between these diagnoses early is imperative, as treatment for each is very different. In our patient, a tumor-like appearance on imaging made the diagnosis of GPA difficult and delayed treatment. Multiple, discrete cavitary pulmonary nodules are common findings in GPA on chest CT. There are few reports of GPA presenting as an inflammatory pseudotumor; most of which also had concurrent cavitary nodules at diagnosis. Our patient never developed discrete cavitary lesions which made distinguishing GPA from malignancy challenging. The positive AFB stain and possibility of active MTB infection also hindered the initiation of steroids and rituximab. A positive AFB stain suggests the presence of Mycobacterium species and should prompt MTB PCR. The sensitivity of MTB PCR can be ˂40% and thus cannot rule out infection. In our patient, empiric treatment for MTB was started given the concern for starting immunosuppression in active infection. Although non-specific, renal dysfunction was crucial in making the correct diagnosis. Kidney injury and hematuria can be present in up to 20% of patients with GPA at the time of diagnosis. In acute GPA, rapidly progressive glomerulonephritis is not uncommon. When kidney involvement is suspected, renal biopsy can often confirm the diagnosis, as was the case in our patient.

Conclusions: GPA can present as an isolated pulmonary mass or cavitary pulmonary nodules which can make differentiating between GPA, malignancy, and MTB infection difficult on imaging alone. A diagnosis of GPA should be confirmed with biopsy. In severe GPA, immunosuppression and plasma exchange should be started urgently and active infections should be treated concomitantly.