A 7 year old male had non blanching rashes over the shin and swelling of knee joint with haematuria +++ and protein +. Microscopic analysis of his renal biopsy specimen is MOST likely to show which of the following?

Presence of non blanching rash with knee joint swelling, hematuria and proteinuria most probably indicates a diagnosis of Henoch Schonlein purpura. Renal involvement is the most potentially debilitating complication of HSP. The most common renal lesion is a focal, proliferative endocapillary glomerulonephritis. Direct immunofluorescence studies done demonstrate IgA deposition in the mesangium. The classic full presentation of HSP includes acute onset of fever, palpable purpura on the lower extremities and buttocks, abdominal pain, ahritis, and hematuria. Cutaneous findings include purpura, uicarial papules, and plaques. Joint disease manifest as ahralgias or ahritis mainly in knees and ankles. 60% develops colicky abdominal pain especially after having food. Ref: CURRENT Diagnosis & Treatment: Rheumatology, 3e chapter 39.