**Question:** A 30 years old male patient presents with complaints of weakness in right upper and both lower limbs of last 4 months. He developed digital infarcts involving 2nd and 3rd fingers on right side and 5th finger on left side. On examination, BP was 160/140 mm Hg, all peripheral pulses were palpable and there was asymmetrical neuropathy. Investigations showed a Hb 12 gm, TLC-12000 Cu mm, Platelets 4,30,000, ESR-49 mm. Urine examination showed proteinuria and RBC - 10-15/hpf with no casts. Which of the following is the most likely diagnosis?

A. Polyarteritis nodosa
B. Systemic lupus erythematosus
C. Diabetes mellitus
D. Vasculitis

**Correct Answer:** C. Diabetes mellitus

**Core Concept:**

The clinical presentation described in the question demonstrates features of vasculitis and neuropathy, which are common manifestations in diabetes mellitus. Vasculitis is an inflammation of blood vessels, leading to reduced blood flow and ischemia, which can result in digital infarcts. Neuropathy is a complication of diabetes mellitus that affects the nerves, leading to weakness and sensory loss.

**Why the Correct Answer is Right:**

Digital infarcts and asymmetrical neuropathy in a young patient with no systemic symptoms suggest a localized vasculitic process. The patient's blood pressure (BP) is high, which is also a common finding in diabetes mellitus.

**Why Other Options are Incorrect:**

A. Polyarteritis nodosa (PAN) is a systemic vasculitis affecting small and medium-sized arteries and veins. Although it can cause neuropathy, it typically presents with more widespread symptoms and signs, making it less likely in this case.

B. Systemic lupus erythematosus (SLE) is an autoimmune disease affecting various organs and tissues, but it does not typically present with digital infarcts and asymmetrical neuropathy.

D. Vasculitis is a broader term encompassing various types of inflammation of blood vessels. While it can cause digital infarcts and neuropathy, it does not explain the high blood pressure in this patient.

**Clinical Pearls:**

Diabetes mellitus is a common cause of digital infarcts and asymmetrical neuropathy, especially in young adults. Its association with hypertension (high blood pressure) is also a common finding. The patient's age, digital infarcts, neuropathy, high blood pressure, and absence of systemic symptoms make diabetes mellitus the most probable diagnosis in this case.