Drug-resistance and its impact on cutaneous tuberculosis

Drug resistance in tuberculosis is a universal health problem, with India and China having the highest number of multidrug resistant tuberculosis (MDR-TB) cases globally. As cutaneous tuberculosis (CTB) accounts for 1.5% of all extrapulmonary tuberculosis, drug resistance in CTB remains less discussed and understood. The sensitivity and specificity of the routine diagnostic workup for CTB are low compared to pulmonary tuberculosis. Therefore, identifying drug resistance becomes challenging and needs a high index of suspicion. Molecular techniques such as polymerase chain reaction (PCR), line probe assays, DNA microarray, and sequencing help us to identify tubercular bacilli and drug resistance early. Prompt initiation of effective therapy reduces disease-related morbidity and mortality and makes the patient non-contagious. Lately, World Health Organization (WHO) has recommended using "all oral longer MDR TB regimen" for pulmonary and extrapulmonary drug-resistant TB instead of a painful older regimen requiring long term therapy with injectables. This review focuses on the drug resistance in CTB, various methods and newer techniques to diagnose them and recent updates on treatment guidelines.