A 5 year old child presents with perivascular IgA deposition and neutrophilic collection. There is erythematous rash on the lower limbs and non – blanching purpura. The likely diagnosis in the child is
**Core Concept**
The child's presentation of perivascular IgA deposition, neutrophilic collection, erythematous rash, and non-blanching purpura suggests an allergic vasculitis, specifically Henoch-Schönlein purpura (HSP). HSP is characterized by IgA-mediated inflammation of small blood vessels, leading to the characteristic skin lesions and systemic symptoms.
**Why the Correct Answer is Right**
Henoch-Schönlein purpura is a form of systemic vasculitis that predominantly affects small vessels, including capillaries, venules, and arterioles. The condition is caused by the deposition of IgA immune complexes in these vessels, leading to activation of the complement system and subsequent neutrophilic infiltration. The resulting inflammation causes the characteristic skin lesions, abdominal pain, and joint symptoms seen in HSP patients. In children, HSP is often triggered by an upper respiratory tract infection, which can stimulate the production of IgA antibodies that eventually deposit in the small vessels.
**Why Each Wrong Option is Incorrect**
**Option A:** While IgA nephropathy is another condition characterized by IgA deposition, it primarily affects the kidneys and is not typically associated with the systemic symptoms and skin lesions seen in HSP.
**Option B:** Kawasaki disease is a medium-vessel vasculitis that can cause fever, rash, and lymphadenopathy, but it is not typically associated with IgA deposition or non-blanching purpura.
**Option C:** Polyarteritis nodosa is a medium- to large-vessel vasculitis that can cause a variety of systemic symptoms, but it is not typically associated with IgA deposition or the characteristic skin lesions of HSP.
**Clinical Pearl / High-Yield Fact**
In children, Henoch-Schönlein purpura often presents with abdominal pain, joint symptoms, and renal involvement, in addition to the characteristic skin lesions. Remember the classic "tetrad" of HSP symptoms: palpable purpura, abdominal pain, joint symptoms, and renal involvement.
**Correct Answer: D. Henoch-Schönlein purpura**