A 7 year old boy presented with intermittent abdominal pain and difficulty walking due to painful knees. He had been previously well except for a mild upper respiratory tract infection approximately one week ago. On examination he seems well but a non-blanching rash was seen on the buttocks and the legs (see photo). The rest of the body was spared.
The non-blanching rash.
Q1. What is the diagnosis?
Q2. What renal complication can occur?
Henoch-Schönlein Purpura (HSP).
Glomerulonephritis.
Henoch-Schönlein Purpura (HSP) is a vasculitis of small vessels. The aetiology is unknown but frequently follows an upper respiratory tract infection.
The rash is usually the cornerstone of diagnosis. It is purpuric and has a characteristic distribution - typically over the buttocks and legs (especially extensor surfaces). The rest of the body is mostly spared although mild trauma can cause further purpura elsewhere on the skin. This phenomenon can result in a linear rash at the ankle caused by pressure from sock elastic (as in this case - examine, carefully, just above the ankles in the photograph).
Colicky abdominal pain is common and joint pain (typically of the knees and ankles) occurs in two thirds of patients. A focal segmental glomerulonephritis is common (about 80% of cases) but is typically mild and usually only manifests by macroscopic or microscopic haematuria.
