Palpable purpura are seen in all EXCEPT:
**Core Concept**
Palpable purpura refers to the presence of purple-colored skin lesions that are palpable (can be felt), typically resulting from small vessel vasculitis. This condition is often associated with autoimmune disorders, infections, and other systemic diseases.
**Why the Correct Answer is Right**
Palpable purpura is a hallmark feature of Henoch-Schönlein purpura (HSP), a form of vasculitis that primarily affects small vessels. HSP is characterized by the deposition of IgA immune complexes in the vessel walls, leading to inflammation and damage. The condition often presents with abdominal pain, arthritis, and renal involvement, in addition to the characteristic skin lesions.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Henoch-Schönlein purpura (HSP) is indeed characterized by palpable purpura, making it a correct association. However, the question asks for an exception, so we'll consider other options.
**Option B:** This option is incorrect because IgA vasculitis, also known as Henoch-Schönlein purpura, is a well-established cause of palpable purpura.
**Option C:** This option is incorrect because systemic lupus erythematosus (SLE) can also cause palpable purpura, although it is less common than in HSP.
**Clinical Pearl / High-Yield Fact**
When evaluating a patient with palpable purpura, it's essential to consider a broad differential diagnosis, including autoimmune disorders, infections, and other systemic diseases. A thorough history, physical examination, and laboratory investigations are necessary to determine the underlying cause of these skin lesions.
**Correct Answer: D.**