<prompt> Lepromin test is seen on:3rd day7th day2nd week4th week  <response>: Ans. d 4th week. Ref. Ananthanarayan, Microbiology, 4th ed. 365Patch test:2nd dyEarly Fernandez reaction:2nd dyInduration in TB seen after:3 dys of tuberculin injectionIn Psoriasis the skin doubling time:4 dysKviem test:2nd week positiveLate Mistsuda reaction:3rd weekNormal skin doubling time:4 weeksLEPROMIN TEST Mitsuda first described lepromin test. Intradermal injection of lepromin antigen is typically biphasic in reaction, early Fernandez reaction characterized by erythema and induration in 24-48 hours and lasting for 3-5 days, analogous to tuberculin test, but of no significance, late is Mitsuda reaction in 4 weeks peak and subsides with ulceration, it is the measure of CMI. Principle of test: Delayed hypersensitivity reaction. Lepromin used:- Uman type- Armadillo type- Dharmendra antigen Purpose of test:- For classification of leprosy- For assessment of prognosis and response to treatment not used for diagnosis- To assess resistance of the individual- To verify the identity of candidate lepra bacillusEducational points:LEPRA REACTIONCharacteristicsType 1Type IIImmunologic basisCell mediatedAg Ab reactionType of hypersensitivityType IVType IIISystemic disturbances-Changes in blood picture-Albuminuria-Type of patientBT, BB, BLBL and LLTreatmentSteroidsThalidomide Clofazimine Continue DapsoneSteroid Drug of choiceLucio phenomenon: Rare reaction in LL due to vasculitis, seen in untreated patients, characterized by tender and red patches and vesicles especially over legs. 