**Question:** A middle-aged man presented with paraesthesia of hands and feet. Examination revealed presence of 'Mees' lines in the nails and raindrop pigmentation in the hands. The most likely diagnosis is: AIIMS 08, 09, 11

A. Systemic sclerosis
B. Systemic lupus erythematosus
C. Scleroderma
D. Raynaud's disease

**Core Concept:**

The question involves a clinical presentation with specific dermatological and nail findings, which are characteristic for certain systemic diseases. Mees' lines are vertical melanin deposition in the nail matrix, while raindrop pigmentation refers to the presence of multiple, small, round, hyperpigmented spots on the nails. These findings are indicative of certain connective tissue diseases.

**Why the Correct Answer is Right:**

The correct answer is **D.** Raynaud's disease. Raynaud's disease is a primary vasculopathy affecting the small blood vessels, particularly in the extremities, leading to episodic digital ischemia and reperfusion, resulting in characteristic dermatological and nail findings. Mees' lines and raindrop pigmentation are specific features of Raynaud's disease.

**Why Each Wrong Option is Incorrect:**

A. Systemic sclerosis (AIIMS 08) and Scleroderma (AIIMS 09) are systemic scleroderma disorders characterized by fibrosis and vascular abnormalities. However, the specific nail findings (Mees' lines and raindrop pigmentation) are not present in these conditions.

B. Systemic lupus erythematosus (AIIMS 11) is an autoimmune disease with multisystem involvement, including skin and mucous membranes. However, the nail findings (Mees' lines and raindrop pigmentation) are not specific for systemic lupus erythematosus.

**Clinical Pearl:** Raynaud's disease is a key clinical entity to recognize, as it is a common cause of digital ischemia and requires appropriate management. It is essential for clinicians to consider Raynaud's disease in patients presenting with paraesthesia and nail changes like Mees' lines and raindrop pigmentation to initiate appropriate management strategies and prevent long-term complications like digital ulcers and gangrene.