A 30-year-old woman with Sjogren syndrome presents with a 24-hour history of a purpuric skin rash. Which of the following is the most likely diagnosis?
**Core Concept**
Sjogren syndrome is a chronic autoimmune disorder characterized by lymphocytic infiltration and destruction of exocrine glands, particularly the salivary and lacrimal glands. The patient's presentation of a purpuric skin rash suggests a vasculitic process, which is a common complication of autoimmune diseases.
**Why the Correct Answer is Right**
The patient's history of Sjogren syndrome and the development of a purpuric rash are highly suggestive of **Henoch-Schönlein purpura (HSP)**, a form of vasculitis that affects small blood vessels. HSP is characterized by the deposition of IgA immune complexes in the walls of small vessels, leading to inflammation and damage. The rash, along with abdominal pain, joint pain, and renal involvement, are classic symptoms of HSP. The presence of IgA deposits in the skin and kidneys is a diagnostic hallmark of HSP.
**Why Each Wrong Option is Incorrect**
* **Option A:** **Lupus nephritis** is a complication of systemic lupus erythematosus (SLE), but it typically presents with renal failure, hypertension, and proteinuria, rather than a purpuric rash.
* **Option B:** **Polyarteritis nodosa (PAN)** is a form of vasculitis that affects medium-sized vessels, but it typically presents with hypertension, renal failure, and organ damage, rather than a purpuric rash.
* **Option D:** **Erythema multiforme** is a skin condition characterized by target-shaped lesions, but it is not typically associated with Sjogren syndrome or vasculitis.
**Clinical Pearl / High-Yield Fact**
HSP is a classic example of a vasculitic process that can occur in the context of autoimmune diseases. The presence of a purpuric rash, along with abdominal pain, joint pain, and renal involvement, should prompt consideration of HSP in the differential diagnosis.
**Correct Answer: C. Henoch-Schönlein purpura (HSP)**