Figure 4 and 5: Histopathological pictures showing poorly formed granulomas consisting of epitheloid cells
DISCUSSION
Cutaneous Tuberculosis (TB) is a relatively uncommon manifestation of extrapulmonary TB (EPTB) accounting for 1-1.5 % of total cases of EPTB.3Cutaneous Tuberculosis is caused by Mycobacterium tuberculosis(MTB) and less commonly by mycobacterium Bovis or Bacillus Calmette-Guerin vaccine.1
Three modes of dissemination of cutaneous TB have been described to date which include primary inoculation, hematogenous spread and contiguous spread.4Modes of primary inoculation include acupuncture, needle stick injury, and insulin injection.1,5
Hematogenous spread of Cutaneous TB is also known in cases of AIDS and chronic kidney diseases.6
Depending on the bacterial load cutaneous TB has been classified as either paucibacillary or multibacillary. Multibacillary forms of cutaneous TB are tuberculous chancre, scrofuloderma, orificial tuberculosis, acute miliary tuberculosis, and metastatic abscess often called tuberculous gumma.1Paucibacillary forms of TB are tuberculosis verrucosa cutis, lupus vulgaris, and tuberculids.1
Tuberculids usually develop as a host hypersensitivity reaction against MTB infection in a visceral organ or distant skin lesion.1,3Tuberculids include papulonecrotic tuberculid, lichen scrofulosorum, erythema induratum of Bazin and nodular tuberculid.1,3
The manifestation of cutaneous miliary TB is not specific.1, 2 Cutaneous manifestation of miliary TB includes erythema, erythematous whitish papules later developing into small vesicles which soon break down to form umbilication and crust formation, and symptoms such as fever, weight loss, and malaise can also be associated .1
Evaluation of Cutaneous TB needs proper history and examination along with relevant laboratory investigations. The investigation includes tuberculin skin test Serum QuantiFERON-TB Gold (QFT-G) levels, PCR, and skin biopsy.7, 8
Other tests include sputum culture and chest x-ray for identification of pulmonary TB and miliary pattern of the disease.7
Our case was diagnosed as cutaneous TB from a skin biopsy with Gene Xpert test.
Since cutaneous tuberculosis almost invariably has a systemic infestation, it is treated in the same manner as a systemic TB.9Multidrug therapy with isoniazid, rifampicin, pyrazinamide, and ethambutol are commonly used drugs.7, 9 The treatment consists of 2 phases, initially intensive phase treatment for 2 months targets at suppressing the bacterial load and a prolonged continuation phase for 4 months emphasizes on the complete elimination of the causative organism.7, 9
Cutaneous TB can be prevented by the BCG vaccine and especially BCG-vaccinated ones have less chance of dissemination forms of TB10