Pauci-Immune Vasculitis cANCA Positive with Renal-Lung Syndrome in Pediatrics: A Case Report

Introduction: Small vessel vasculitis associated with neutrophil cytoplasm antibody (ANCA) presents with mild to severe clinical presentations, including renal failure and eye involvement. It is a rare disease with an incidence of 13-20 cases per million people globally, with an annual prevalence of 46-184 cases per million. In children, the incidence is 10-20 cases per million inhabitants per year, predominantly female. Clinical case: A 5-year-old female patient presented with fever, cough, and hemoptysis. Laboratory tests revealed severe anemia, and acute renal injury. During admission, she suffered from nephritic syndrome with hypertension, hematuria, and non-nephrotic proteinuria. A renal biopsy revealed diffuse extracapilar proliferative glomerulonephritis, both active and chronic, pauci-immune type. Steroid and immunomodulator administration were effective, achieving clinical improvement and hematological recovery. Outpatient management was continued with prednisone and cyclophosphamide for 3 months, followed up every 6-12 months by pediatrics. Discussion: A case is presented of a female patient with lung-kidney syndrome secondary to cANCA-positive vasculitis. This vasculitis, associated with anti-neutrophil cytoplasmic antibodies, is a rare disease characterized by necrotizing inflammation of small blood vessels. The lung-kidney syndrome manifests with alveolar hemorrhage and glomerulonephritis, with vasculitis being one of its most common causes. Its etiology is unknown and appears to result from a complex interaction between genetic, environmental, and immune dysregulation. In the literature, a predominance of the female sex has been observed in ANCA-associated vasculitis in children, although the patient in this case began to show symptoms at an earlier age than usual. Pulmonary symptoms include dyspnea, chronic cough, and hemoptysis, while renal involvement is manifested by abnormal urinalysis and glomerulonephritis confirmed by biopsy. Diagnosis relies on the determination of ANCA antibodies and histopathological studies, which in this case showed scar lesions in the glomeruli. For treatment, the EULAR recommendations were followed, using cyclophosphamide and glucocorticoids, resulting in a favorable evolution of the patient. Conclusion: Systemic vasculitis, a rare childhood disease, requires high suspicion rate and timely treatment, especially in children with lung-kidney syndrome, to improve survival rates.