**Question:** An 18 years old boy presents with digital gangrene in third and fourth finger for last 2 weeks. On examination the blood pressure is 170/110 mm of Hg and all peripheral pulses were palpable. Blood and urine examinations were unremarkable. Antinuclear antibodies, Antibody to double-stranded DNA, and antineutrophil cytoplasmic antibody were negative. The most likely diagnosis is

A. Raynaud's disease
B. Polyarteritis nodosa
C. Takayasu's arteritis
D. Giant cell arteritis

**Core Concept:** Giant cell arteritis (GCA) is a form of vasculitis, a condition characterized by inflammation of blood vessels. In GCA, immune system attacks the medium and large arteries, particularly the temporal arteries, leading to ischemic complications.

**Why the Correct Answer is Right:** In this case, the patient presents with digital gangrene in the third and fourth fingers, which is a characteristic feature of GCA. Additionally, the patient has a high blood pressure (170/110 mmHg) and all peripheral pulses are palpable, which is in contrast to Raynaud's disease (Raynaud phenomenon is characterized by absent pulses).

The negative antinuclear antibodies, Antibody to double-stranded DNA, and antineutrophil cytoplasmic antibody tests rule out other conditions like Raynaud's disease (which is associated with positive autoantibodies), Polyarteritis nodosa, and Takayasu's arteritis (which usually present with more severe symptoms, systemic involvement, and positive autoantibodies).

**Why Each Wrong Option is Incorrect:**

**A. Raynaud's disease:** Although Raynaud's disease can present with digital gangrene, it is characterized by absent pulses, not palpable pulses.

**B. Polyarteritis nodosa:** Polyarteritis nodosa is characterized by systemic involvement, severe symptoms, and positive autoantibodies, which are not present in this case.

**C. Takayasu's arteritis:** Takayasu's arteritis typically presents with systemic involvement, severe symptoms, and positive autoantibodies, which are not present in this case.

**D. Giant cell arteritis:** GCA is the correct answer as it presents with digital gangrene, high blood pressure, and negative autoantibodies.

**Clinical Pearls:**

1. Recognize the characteristic presentation of GCA, which includes digital gangrene due to arterial occlusion, hypertension, and negative autoantibodies.
2. GCA is a form of vasculitis affecting medium and large arteries, and presents with symptoms like headache, jaw claudication, fever, and scalp tenderness.
3. The diagnosis of GCA is typically made based on clinical presentation, exclusion of other causes (like autoimmune disorders, infections, and vasculitis syndromes), and finding of temporal artery biopsy showing giant cells.
4. Treatment includes corticosteroids and may also involve immunosuppressants like methotrexate.

**Why the Wrong Options are Less