A 12 year old boy had a gradually progressive plaque on a buttock for the last 3 years. The plaque was 15 cm in diameter, annular in shape, with crusting and induration at the periphery and scarring at the center. The most likely diagnosis.

Ans. is 'c' i.e. Lupus vulgarisRef. Roxburgh 16th/e page 41, Pasricha 4th/e page 92, Behl 8th/e page 203 A lesion with central scarring in a 12 year old boy gradually, progressing over 3 years is quite suggestive of Lupus vulgaris * RememberFeatureDiseaseInvestigationCentral clearing Central scarringCentral crustingTinea corporis Lupus vulgaris LeishmaniasisKOH smar BiopsyLD body demonstrationClinical features of Lupus vulgarisCommonest manifestation of cutaneous tuberculosisMost frequent age group is children and young adultsIt usually affects the exposed areas of the body. Face is the most common site. The lesion is asymmetrically distributed. Can also affect hands, feet, knees and buttockThe lesion starts as reddish brown macule and enlarges slowly over months and years to form big patch with a well-defined but irregular margin.The diagnostic features are: -Persistent brownish-red, well defined patch with dermal infiltrationPresence of apple jelly nodulesOn healing a, tissue paper like scarring is produced in the centreMatch stick test positive - An apple jelly nodule has no resistance to pressure by a sharp match stickLong history expanding over yearsTuberculin testpositive.3 Miliary tubercles in a biopsy specimenDiagnosis of Lupus vulgaris is made by - Biopsy