Ans. d (4th week). (Ref. Ananthanarayan, Microbiology, 4th ed. 365)Patch 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 (positive)Late 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 choice)Lucio phenomenon: Rare reaction in LL due to vasculitis, seen in untreated patients, characterized by tender and red patches and vesicles especially over legs.