A 50-year-old drug abuser presents with fever and weight loss. Exam shows hypeension, nodular skin rash, and peripheral neuropathy. ESR is 100 mm/L, and RBC casts are seen on urinalysis. (SELECT 1 DIAGNOSIS)
**Core Concept**
The patient's presentation suggests a systemic disease characterized by hypertension, nodular skin rash, peripheral neuropathy, and renal involvement, likely due to an immune-mediated response.
**Why the Correct Answer is Right**
The patient's symptoms are indicative of **Wegener's Granulomatosis** (Granulomatosis with Polyangiitis, GPA), a form of vasculitis that affects small- and medium-sized vessels. The presence of nodular skin rash, peripheral neuropathy, and RBC casts on urinalysis, along with elevated ESR, suggests renal involvement. GPA is often associated with the presence of **c-ANCA (cytoplasmic anti-neutrophil cytoplasmic antibodies)**, which targets the enzyme proteinase 3 (PR3).
**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely a distractor representing a different type of vasculitis, such as **Polyarteritis Nodosa (PAN)**, which primarily affects medium-sized vessels and is not typically associated with c-ANCA or renal involvement.
**Option B:** This option may represent **Sarcoidosis**, which can present with skin rash and peripheral neuropathy but is not typically associated with hypertension, renal involvement, or elevated ESR.
**Option C:** This option could be a distractor for **Diabetic Nephropathy**, which is associated with peripheral neuropathy and renal involvement but does not typically present with hypertension, nodular skin rash, or elevated ESR.
**Option D:** This option may represent **Lupus Nephritis**, which can present with renal involvement and elevated ESR but is not typically associated with c-ANCA or the specific constellation of symptoms seen in this patient.
**Clinical Pearl / High-Yield Fact**
Wegener's Granulomatosis (GPA) is a classic example of a small-vessel vasculitis that can present with a wide range of symptoms, including renal involvement, skin rash, and peripheral neuropathy. The presence of c-ANCA (PR3 ANCA) is a key diagnostic clue, and prompt recognition is essential to initiate timely treatment.
**Correct Answer:** C.