P0626 - A Can’t-Miss Diagnosis at an Unusual Age: An Adolescent with Granulomatosis with Polyangiitis

Case Description:
A 16-year-old previously healthy male presented with acute onset, right-sided pleuritic chest pain. The pain was preceded by two days of non-productive cough, two weeks of night sweats, and an 18-pound weight loss in one year. He denied fevers but admitted to vaping tobacco and THC. He denied sick contacts and travel but had been living in a group home for three years. On arrival, he was tachycardic and tachypneic but afebrile. He was diaphoretic and breathing shallowly. On auscultation, he had crackles in the right lateral lung fields. WBC was 15.8 K/μL with hemoglobin of 11.8 g/dL and platelets of 399 K/μL. Creatinine was 0.76 mg/dL. CRP was 145.7 mg/L and ESR of 50.0 mm/hr. Uric acid and LDH were normal. Respiratory viral panel and HIV were negative. Urinalysis showed 19 RBCs but no proteinuria. ECG was unremarkable. Chest X-ray showed bilateral pulmonary nodules. Computed tomography (CT) disclosed multiple mixed solid and cavitary thick-walled pulmonary nodules, some containing dystrophic calcifications. CT did not show any axillary, mediastinal, or hilar lymphadenopathy. The differential diagnosis at this point included tuberculosis, fungal infections, endocarditis, vaping-related lung injury, sarcoidosis, malignancy, and vasculitis. AFB smear/cultures along with blastomycosis, histoplasmosis, and cryptococcal antigens were not detected. Interferon-γ release assay tests for tuberculosis were negative. Transthoracic echocardiogram was normal. Bronchoscopy was unrevealing. Myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA) and antinuclear antibody (ANA) were negative. Rheumatoid factor was 13. CT of sinuses and renal ultrasound were normal. 24-hour urine protein was normal yet repeat urinalysis showed 12 RBCs. Proteinase 3 antineutrophil cytoplasmic antibody (PR3-ANCA) was positive at 362 AU/mL. While awaiting lung biopsy, he developed hemoptysis and was started on prednisone and rituximab. Lung biopsy showed acute arteritis and capillaritis with zonal necrosis and granulomatosis consistent with granulomatosis with polyangiitis (GPA). His disease is improving on rituximab and prednisone.

Discussion:
Pediatric-onset GPA is a rare, life-threatening vasculitis with an incidence of 1.8 cases/million person-years. Although uncommon, GPA-related deaths can occur due to opportunistic infections or pulmonary hemorrhage. While primarily a disease of middle age, this diagnosis must be made swiftly as approximately 63% of pediatric patients suffer organ damage just 12 months following induction therapy. The sooner we diagnose and treat these patients, the better chance they have at remission and preserved organ function into adulthood.