Cutaneous Tuberculosis

Tuberculosis can affect any part or organ of the body. Tuberculosis of skin is a common disease in regions where the prevalence of TB infection is high as in India. The skin may be directly infected by the TB bacilli or the manifestations on the skin may be secondary to TB infection in other organs of the body. Skin tuberculosis can have varied manifestations as given below
1.    Lupus vulgaris
2.    TB verrucosa cutis
3.    Scrofuloderma
4.    TB chancre
5.    Acute military TB of skin
6.    Lichen scrofulosorum
7.    Papulonecrotic tuberculids
8.    Erythema nodosum
9.    Erythema induratum
10.   Bruli ulcer
11.   Swimming pool granuloma
12.   TB gumma
13.   TB cutis orificialis
14.   BCG vaccination related skin lesions
 
Modes of Entry
1) TB bacilli enters the skin through minor abrasion or injuries of the skin as in TB chancre, swimming pool granuloma, bruli ulcer.
2) Hematogenous spread of TB from foci in another organ of body as in acute military TB of skin and subcutaneous TB gumma.
3) Immune mediated mechanisms in response to TB in another organ of the body as in Lichen scrofulosorum, Papulonecrotic tuberculids, Erythema nodosum, Erythema induratum
4) In response to BCG vaccination
5) Contiguous spread from an adjacent structure like bone to skin or lymph node to skin.
6) May affect the orifices; mouth and the perianal region when the bacilli is discharged from pulmonary or abdominal TB and autoinnoculated at the orifices
 
Diagnosis involves biopsy and histopathological examination of the skin lesions. Very rarely the TB organism can be found in the smear or culture of the specimen. Histopathology reveals granulomatous dermatitis. Mantoux test and PCR for TB may be positive but are non-specific. If TB is strongly suspected clinically but the investigations are inconclusive, a 6 week trial of anti-TB drugs can be given. In case of improvement the anti-TB drugs are continued or alternate diagnosis should be entertained.
 
Treatment
Anti tuberculosis therapy for 6 to 9 months as per dermatologist advice. National guideline of India recommends 6 month treatment with 3 anti-TB drugs in the first 2 months and 2 anti-TB drugs for the next four months.