Appendicitis as first presentation of aggressive granulomatosis with polyangiitis and diffuse alveolar haemorrhage.

Acute respiratory distress syndrome (ARDS) can be associated with a wide multiplicity of causes, including diffuse alveolar haemorrhage (DAH). Vasculitis associated with anti-neutrophil cytoplasmic antibody (ANCA), particularly granulomatosis with polyangiitis (GPA), is one of the most common causes of DAH, primarily affecting small and medium-sized vessels in the lungs and kidneys. Diagnosing GPA can be challenging, and it should be considered a potential cause of DAH, even in the absence of other organ involvement. Given the high mortality associated with this condition, early diagnosis and aggressive treatment are crucial for improving outcomes. We present the case of a young patient with severe ARDS who did not show significant alveolar haemorrhage on bronchoscopy or renal involvement but exhibited extensive gastrointestinal involvement and had a predominant laboratory diagnosis of positive cytoplasmic anti-neutrophil cytoplasmic antibody and proteinase 3 antibodies.