A 30-year-old veterinarian develops a skin papule on his hand 10 days after handling stillborn lambs, which slowly enlarges into a painless haemorrhagic blister with central necrosis and marked oedema but absent local tenderness. Gram stain of lesion exudate shows large Gram-positive rods. The MOST likely diagnosis is:

• A Cutaneous leishmaniasis
• B Staphylococcal carbuncle
• C Tularemia
• D Cutaneous anthrax ✓

Explanation

Cutaneous anthrax (caused by Bacillus anthracis) classically presents as a painless papule progressing to a haemorrhagic eschar with extensive surrounding non-pitting oedema — the 'malignant pustule'. The organism is a large, encapsulated, Gram-positive, spore-forming rod; the characteristic absence of pain and marked oedema distinguish it from staphylococcal infections. Occupational exposure to livestock and animal products is a strong clue.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.