Tuberculosis of skin: watch out for it!!!

Cutaneous tuberculosis (TB) is the affliction of skin by Mycobacterium tuberculosis. It iscommonly known that TB affects the lungs, the bones and maybe the stomach but it also affects the skin, and it usually goes unrecognized. Its symptoms and features are so innocuous and common, that physicians and patients both keep mistaking it for common maladies and treating it accordingly. The incidence of TB had decreased over the years due to advent of multi-drug regimens but with the rise of HIV and poor patient compliance the occurrence of skin TB cases has again seen an increase. Skin TB accounts for only 0.1-2% of the global TB burden with an incidence of 5.9 cases per 1000 population.
Modes of spread: Transmission can be both endogenous and exogenous. Endogenous spread means spread from a pre-existing focus of infection, usually intestinal or lung TB. Dissemination can be hematogenous, contiguous or lymphatic. Exogenous transmission means acquisition of infection from the outside by inoculation.
The type of infection depends upon individual’s immune status and mode of spread.
Types of cutaneous TB:
1. Tuberculous chancre: It is a rare type which occurs in people with low immunity to TB. It occurs by direct inoculation of TB bacteria into the skin, and leads to development of a
reddish- brown papule that slowly progresses to a bleeding, soft, painless and chronic ulcer. Face and extremities are commonly involved sites.
2. Tuberculosis verrucosa cutis (TVC): It occurs via inoculation in people with high grade immunity against TB. In our country commonly seen in children on buttocks and
extremities on account of playing barefoot or in the soil. Lesions present as single warty growths on trauma prone areas for long term. Lesions can slowly spread and attain large
sizes and are usually mistaken for warts.
3. Scrofuloderma: Also known as Tuberculosis colliquativa cutis, and is the most common form of skin TB in India. It occurs by contiguous spread onto the skin from adjacent infected structures like bones, testis and most commonly lymph nodes. Lesions present as painless purplish-pink nodules that my spontaneously ulcerate or form fistulae. It occurs usually in children and elders and leaves atrophic ugly scars when they heal.
4. Orificial tuberculosis: It occurs in middle-aged and elderly with loss of immunity and concurrent occurrence of severe urinary, lung or gastrointestinal TB. Lesions present as yellowish soft nodules or friable bleeding ulcers around the mouth, nose, anus or urinary orifice.
5. Lupus Vulgaris: This form occurs in patients with high immunity against TB bacillus. Commonly the lesions are seen on legs and buttocks, especially in children in developing countries. It commonly presents as reddish-brown nodular lesions that keep spreading over large areas. Areas of ulceration are seen. The disease spreads by peripheral extension of ulcers and healing by scarring of older areas of involvement. Cancer of skin can develop in long-standing older lesions and cosmetic disfigurement is common.

6. Tuberculous gumma: This presents in malnourished children and elders with low immune status, like HIV or cancer patients. Multiple fluctuating subcutaneous nodules or cold abscesses occur all over the body and may sometimes ulcerate.

7. Acute military TB: It is a very rare and severe form in immunocompromised patients with full body dissemination of TB bacilli. A patient can have reddish purple tiny nodular lesions which can sometimes ulcerate and heal with scarring. Fever, loss of weight and appetite are associated features.
Tuberculids: These are uncommon and often missed presentations due to hypersensitivity to TB bacilli and antigens:
1. Papulonecrotic tuberculid: it is the most common type and seen in young adults and children as reddish purple, tiny lesions on the abdomen, back, legs and hands that may ulcerate resembling tiny volcanoe-like lesions. Lesions resolve in few weeks leaving behind pox-like scars.
2. Lichen scrofulosorum: It is again seen in young adults as crops of reddish-brown tiny papules all over the body that heal with no scarring.
3. Erythema induratum of Bazin: It affects middle-aged females as painful nodular lesionds on back of legs.
Investigations:
A careful look-out coupled with a few tests can help clinch the diagnosis. Immunity to TB bacilli can be checked by Mantoux test in which TB antigen is injected on the forearm and reaction to it is noted after 2 days. A skin biopsy can be taken and looked for TB bacillus. PCR can be done on the biopsy sample in which DNA amplification is done and is more specific to identify TB. Chest X-ray can show lung involvement and complete blood tests are also supplementary tests.
Treatment:
The government with the aid of WHO has introduced TB-DOTS (directly observed treatment, short course) as the most cost-effective way of treating TB. A combination of drugs is given under supervision from 6 months to 1 year according to the severity and type. The drugs initially included were isoniazid, rifampicin, pyrazinamide, and ethambutol. A dose is adjusted according to weight. Common side effects include flu, malaise, acne-like lesions, nausea, vomiting, red-colored urine. Few serious complications include neuritis and hepatitis. Initially, DOTS proved successful in controlling the TB epidemic but the rising drug resistance has posed significant problems. Resistance has arisen to multiple primary as well as second-line drugs.

MDR-TB: TB resistant to at least two of the first-line medications: isoniazid and rifampicin. The treatment regimen then involves second-line and injectable drugs as well as longer treatment duration.


XDR-TB: Extensively drug-resistant TB is a rare MDR-TB with resistance to isoniazid, rifampicin, plus any fluoroquinolone and at least one of the three injectable second-line drugs (amikacin, kanamycin or capreomycin).
Skin TB is an often overlooked entity and hence remains unrecognized for long periods leaving behind scars, debilitation, and stigma. The prejudices and fears associated with the
word TB amongst the laymen prevent adequate and timely treatment. The rising drug resistance is another problem that needs to be combated. Hence both the physician and the patient should keep a sharp lookout for the disease and take full and adequate treatment.

 

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