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Cutaneous mycobacterial infections are chronic granulomatous lesions affecting skin at various regions of the body. Micro-biologically they are classified as follows:

  1. Tuberculous, Pathogenic
    M tuberculosis          M bovis          M lepra          M africanum
  2. Non-Tuberculous, Potentially Pathogenic


Mycobacteria causing skin infections
• Post-trauma abscess



M. chelonae
M. fortuitum
M. terrae
• Swimming pool granuloma
• Buruli ulcer
• Lupus vulgaris
• Scrofuloderma
M. marinum (M. Balanei)
M. ulcerans
M. tuberculosis
M. tuberculosis
  1. Clinical Features
    There are different clinical presentations in cutaneous tuberculous infections, depending on the virulence and number of bacilli infected, immunological status of the host and the route of infection. Traditionally the clinical types are divided into two groups:

  1. True cutaneous tuberculosis
    1. Lupus vulgaris             
    2. Tuberculous verrucosa cutis
    3. Scrofuloderma     
    4. Tuberculous chancre, gumma, cold abscess     
    5. Miliary tuberculosis
  2. Tuberculids
    1. Papulonecrotic tuberculid     
    2. Lichen scrofulosorum     
    3. Erythema induratum
Exogenous Source Endogenous Hypersensitivity

•  Tuberculosis chancre (primary inoculation TB)
•  Tuberculosis verucosa cutis

•  Lupus vulgaris
•  Scrofuloderma
•  Orificial tuberculosis
•  Miliary tuberculosis
•  Metastatic tuberculous abscess
•  Gumma

•  Tuberculids
•  Lichen scrofulossorum
•  Papulo-necrotic
•  Erythema induration
•  Erythema nodosum

Tuberculids Characteristic features
Papulonecrotic •  Necrotic centre over papules, on extensor of extremities, elbow, knee back, face, Palms & Soles.
•  Lesions heal with varioliform scarring.
•  Histologically there is obliterative vasculitis in addition to a tuberculoid granuloma with caseation.
Lichen scrofulosorum •  Scaly grouped micorpapular rash over trunk especially in young girls.
•  Lesions heal without scarring (in contrast to papulonecrotic).
•  Histological hallmark is superficial epitheloid dermal granulomas surround hair follicles and sweat ducts (AI09) and may occupy several dermal papillae. Caseous necrosis is usually not seen.
Erythema induratum (Bazin's disease) •  Painful nodules over the back or sides of the legs of young women.
•  Lesions may break down which form ulcers, Ulcers heal with scarring.
•  Histologically there is vasculitis and granulomatous panniculitis.
  1. True Cutaneous Tuberculosis
    1. This group of cutaneous tuberculosis is infected through direct inoculation from an exogenous source, contiguous or haematogenous spread from an endogenous focus.
  1. Lupus Vulgaris (L.V.)
    1. This is a chronic, progressive and tissue-destructive form of cutaneous tuberculosis in patient with moderate or high degree of immunity. It occurs more common in females than in males.
    2. The classical lesions consist of reddish-brown plaque with "apple-jelly" colour on diascopy.
    3. The lesions progress by peripheral extension and central healing, atrophy and scarring.
    4. The areas of predilection are head and neck (80%), followed by arms and legs, then trunk.
    5. It can be associated with tuberculosis of lymph node, lung, bone and joint.

In long-standing cases, patients may have scarring, deformity, squamous cell carcinoma, basal cell carcinoma or sarcoma.


The main differential diagnosis includes discoid lupus erythematosus, sarcoidosis, leprosy, lupoid leishmaniasis, tertiary syphilis, deep fungal or atypical mycobacterial infection, granulomatous rosacea and Wegener's granulomatosis.


Lupus Vulgaris (L.V.)

  1. Tuberculosis Verrucosa Cutis (TBVC)
    this condition is common in boys over the buttocks and knees. This is mainly due to their habit of playing and squatting in the streets with open-bottom trousers. It usually presents as an indolent, purplish or brownish red, warty and hyperkeratotic plaque lesion. It affects patients with moderate or high immunity through direct inoculation of the tubercle bacilli at sites of trauma. The areas of predilection are therefore over the buttock, knee, elbow, hand and finger. Its progression is usually very slow and spontaneous resolution may occur. This condition must be differentiated from lupus vulgaris, viral wart, mycobacteria marinum infection, chromomycosis, tertiary syphilis and hypertrophic lichen planus.

  1. Scrofuloderma
    This results from direct extension of an underlying tuberculous focus such as lymph node, bone or joint to the overlying skin. It is characterized by undermined ulcers, nodules, fistulae, sinuses and scar. The areas of predilection are neck, supraclavicular fossae, axillae and groin. The differential diagnosis mainly includes hydradenitis suppurativa, actinomycosis, sporotrichosis and atypical mycobacterial infection.


  1. Tuberculids
    It has been postulated that tuberculids are the result of hypersensitivity reaction to haematogenous dissemination of tubercle bacilli or their toxin in patients with moderate or high degree of immunity.
  2. Papulonecrotic Tuberculid
    This condition usually presents with symmetrical crops of papular eruption that proceed to central necrosis, ulceration and depressed scar. It occurs predominantly in young adult, most commonly affecting the limbs. There may be history or distant foci of tuberculous infection. The main differential diagnosis includes prurigo simplex, papular eczema, folliculitis, leukocytoclastic vasculitis, pityriasis lichenoides et varioliformis acuta and secondary syphilis.
  3. Lichen Scrofulosorum
    This is a rare form of tuberculid, presenting with grouped lichenoid papules with perifollicular pattern over the trunk. It is frequently found in children or young adults and may be associated with tuberculosis of lymph node, bone or joint. The lesions often involute slowly in months without scar and then recur. This condition must be differentiated from lichenoid drug eruption, lichen nitidus, keratosis spinulosa, sarcoidosis, lichenoid syphilis and eruptive syringoma.
  4. Erythema Induratum (Bazin)
    This is a nodular tuberculid presenting with indolent inflamed deep-seated nodule and plaque, occurring bilaterally over the calves or feet. In severe case there may be necrosis, ulceration, depressed scar and pigmentation. It is more common in females than males. Usually there is no evidence of other distant tuberculous foci. The main differential diagnosis is erythema nodosum and other forms of nodular vasculitis.
  5. Mycobacteria Marinum Infection (Swimming pool or fish tank granuloma)
    This is a chronic granulomatous infection of the skin caused by M marinum, acquired by inoculation through abrasions. It is more vulnerable in children and adolescents who frequently go to swimming pools, and among fishermen and fishmongers. The lesion commonly occurs on fingers, knuckles, elbows, knees and feet. Clinically it presents as an inflamed nodule, pustule, ulcer or abscess. Sporotrichoid spread may occur. The main differential diagnosis includes lupus vulgaris, sporotrichosis and leishmaniasis.

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