<prompt> Yellow fluorescence on wood;s lamp is seen in -Tuberous sclerosisPseudomonas infectionTinea versicolorErythrasma  <response>: PITYRIASIS VERSICOLOR:-Tinea versicolor.Macules with fine scaling.Causative organism: dimorphic fungi.genus Malassezia globosa and M.furfur. Clinical features:- Hypohyperpigmented macules with fine ,branny scales. The lesions may coalesce to involve large areas,forming map like structures. Scraping the surface will accentuate the scaling,known as scratch sign or coup dongle sign or Besnier sign. Sites involved-upper trunk mainly. Also affect face and flexural areas. Investigation:- Woods lamp examination - golden yellow flourescence. Scraping and direct microscopy after adding KOH will demonstrate presence of both yeast and hyphal forms.This appearance is called as spaghetti and meatball appearance. Tuberous sclerosis gives a bluish white flourescence with woods lamp examination.The macules with their long axis longitudinally distributed on the limbs and transversly on the trunk are seen more on woods lamp examination. Erythrasma- causative organism- corynebacterium minutissimum shows coral red flourescence due to production of coproporphyrin 3. Pseudomonas:Contains pigments pyoverdin or fluorescein giving green flourescence. Reference: IADVL textbook of dermatology, page 109. 