Case Presentation: A 69-year-old Peruvian female with a remote history of endometrial cancer initially presented to her primary care physician with one week of subjective fevers, night sweats, bilateral ear pain and sore throat. She was prescribed amoxicillin-clavulanic acid and chest x-ray was ordered. She returned three days later with persistent symptoms. Chest x-ray from prior visit showed new left upper lobe clustered nodular opacities which prompted referral to the emergency department to rule out tuberculosis (TB).

On presentation, she was afebrile with unremarkable physical exam. Lab analysis showed leukocytosis of 18 x 109/L, serum creatinine of 1.2 mg/dL and urinalysis with microscopic hematuria. Chest CT with contrast showed bilateral scattered solid nodules with poorly defined groundglass rim. She was placed on airborne isolation to rule out TB. She continued to spike intermittent fevers and had persistent microscopic hematuria. Infectious workup, including three acid-fast bacilli smears, was negative. Her p-ANCA antibody was found to be positive at 43 and ESR and CRP were markedly elevated. She underwent VATS lung biopsy which showed organizing pneumonia with hemorrhage and foci of neutrophilic capillaritis. A diagnosis of microscopic polyangiitis was made. She was started on isoniazid for latent TB infection (LTBI) and was treated with pulse dose steroids with improvement in her serum creatinine, hematuria and inflammatory markers. She was discharged home with plan for rituximab therapy as an outpatient. 

Discussion: Microscopic polyangiitis (MPA) is a systemic small vessel vasculitis characterized by the presence of circulating ANCAs, most commonly p-ANCA or myeloperoxidase (MPO) antibody. Patients typically present with constitutional symptoms and subsequently develop pulmonary and renal manifestations. Common upper respiratory manifestations include rhinosinusitis and otalgia. Chest radiograph may show nodules, patchy or diffuse opacities and hilar adenopathy. Renal involvement is essentially universal and typically manifests as asymptomatic hematuria. A positive ANCA test strongly suggests the diagnosis of vasculitis but biopsy should be performed to confirm the diagnosis. Initial immunosuppressive therapy consists of glucocorticoids plus either cyclophosphamide or rituximab.

Conclusions: This case highlights the importance of recognizing when recurrent fever and abnormal chest radiography in a patient from a TB-endemic area may be something more serious. Early diagnosis of MPA is critical as mortality is highest in the first months after diagnosis. Since treatment of MPA consists of immunosuppressive therapy, this case also highlights the importance of ruling out TB as MPA treatment may cause reactivation of LTBI.