Skin manifestations of tuberculosis

• Lupus vulgaris usually arises as a post-primary infection. It usually presents on the head or neck with red-brown nodules which look like apple jelly when pressed with a glass slide. They heal with scarring, and new lesions slowly spread out to form a chronic solitary erythematous plaque. Chronic lesions are at high risk of developing squamous cell carcinoma.
• Tuberculosis verrucosa cutis arises in people who are partially immune to tuberculosis but who suffer a further direct inoculation in the skin. It presents as warty lesions on a ‘cold’ erythematous base.
• Scrofuloderma arises when an infected lymph node spreads to the skin causing ulceration, scarring and discharge.
• The tuberculides are a group of rashes caused by an immune manifestation of tuberculosis rather than direct infection. Erythema nodosum is the commonest. Erythema induratum (’Bazin’s disease’) produces similar deep red nodules but these are usually found on the calves rather than the shins and they often ulcerate.