Cutaneous tuberculosis

March 5 2020

I spent the day in the Dermatology Clinic today and saw a wide variety of common and interesting dermatologic cases! In the morning, we saw a patient that had been referred by the Tuberculosis Clinic for possibility of cutaneous manifestations of TB. Cutaneous lesions are a relatively uncommon manifestation of TB, occurring in only 1-2 % of infected patients. Therefore our staff spent some time discussing the various dermatologic presentations seen in TB.

The clinical variants of cutaneous TB are divided into: infectious acquired through exogenous inoculation, infectious that result from contiguous spread from nearby structures, infectious related to hematogenous dissemination, and the tuberculids, which are thought to be hypersensitivity reactions to M. tuberculosis.

Exogenous inoculation:

• Primary inoculation TB (tuberculous chancre): results from direct entry of organism into the skin or mucosa of someone previously not sensitized to M. tuberculosis. Lesions appear as red-brown papules or nodules that evolve into painless, shallow ulcers. The face and extremities are most commonly affected.
• Tuberculosis verrucosa cutis: occurs after direct inoculation of mycobacteria into the skin of previously  sensitized host. Lesions are usually painless, violaceous, indurated plaques, appearing on the fingers and dorsum of hands.

Contiguous spread:

• Scrofuloderma (tuberculosis colliquativa cutis): results from extension of the infection from a deep structure (eg lymph node) into the skin. Lesions appear as firm, painless, subcutaneous, red-brown nodules. The neck, axillae and groin are often involved.
• Tuberculosis cutis orificialis: develops in individuals with advanced TB of the GI tract, lungs, GU tract and impaired cell-medicated immunity. Lesions occur in the nasal mucosa, oral mucosa or anogenital skin/mucosa and appear as red-yellow nodules that break down to form painful, punched-out, friable ulcers.
• Lupus vulgaris (tuberculosis lupus): represents reactivation of TB infection and is a chronic and progressive form of cutaneous TB. It can result from either direct extension from an underlying focus or via lymphatic or hematogenous spread. It appears as collection of discrete, red-brown papules that coalesce to form an indolent plaque.

Hematogenous spread:

• Metastatic tuberculous abscesses (tuberculous gummas): occurs from the spread of mycobacteria to subcutaneous tissues. Patients present with a single or multiple, nontender, fluctuant, subcutaneous nodules, which eventually penetrate the skin and form ulcers.
• Acute miliary tuberculosis: results from the hematogenous dissemination of mycobacteria from a focus of infection. Cutaneous manifestations are rare but can present as pinpoint red-blue or purpuric papules with overlying tiny vesicles that then become umbilicated and crusted.
• Lupus vulgaris

Tuberculids:

• Papulonecrotic tuberculid: presents as firm, dark red or purple papules that are symmetric and often recurring. They subsequently become pustular and necrotic. Lesions occur on the face, ears, extensor surfaces and buttocks.
• Lichen scrofulosorum: collection of firm, yellow-red to red-brown papules that are follicular and often found on the trunk.
• Erythema induratum of Bazin (nodular vasculitis): presents as mildly tender, dull red, subcutaneous nodules on the lower legs. Nodules can break down and form deep, draining ulcers.

In our case, the patient did not end up having any cutaneous manifestations of tuberculosis. However, this case allowed me to learn about the various dermatologic presentations that can be seen in TB patients. Overall, the day was a fantastic opportunity to gain more exposure to dermatologic presentations and to review the many cutaneous manifestations seen in systemic diseases!

-MB-

References:

1. Handog EB, Macarayo MJE, Rosen T (Ed.). Cutaneous manifestations of tuberculosis. UpToDate. Accessed on March 5 2020 from: https://www-uptodate-com/cutaneous-manifestations-of-tuberculosis.