This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oncology, Subject name: Medicine
A 14-year-old girl develops a rash, abdominal pain, and arthralgias. She is also experiencing some nausea, vomiting, and crampy abdominal pain. On examination, she has a palpable purpuric rash on her buttocks and lower legs, a tender abdomen, and no active joint inflammation. Her stools test positive for blood, and urinalysis reveals RBCs and RBC casts. Her renal function deteriorates rapidly over several days. A renal biopsy is performed.For the above patient with GN, select the most likely diagnosis on renal biopsy. 
Select and explain. 
A. diffuse proliferative GN, B. crescentic GN, C. focal proliferative GN, D. membranoproliferative GN
A: diffuse proliferative GN
Answer: A: diffuse proliferative GN 
Explanation: This is a case of Henoch-Schonlein purpura (HSP). Diffuse proliferative GN is characterized by acute nephritic syndrome: AKI over days to weeks, with hypertension, edema, oliguria, and active urine sediment. Less severe clinical presentation correlates with a more benign biopsy. The pattern of glomerular involvement is similar to IgA nephropathy.