Yellow fluorescence on wood&;s lamp is seen in -

PITYRIASIS VERSICOLOR:-Tinea versicolor.Macules with fine scaling.Causative organism: dimorphic fungi.genus Malassezia globosa and M.furfur. Clinical features:- Hypo/hyperpigmented 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 d'ongle sign or Besnier sign. Sites involved-upper trunk( mainly). Also affect face and flexural areas. Investigation:- Wood's 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 wood's lamp examination.The macules with their long axis longitudinally distributed on the limbs and transversly on the trunk are seen more on wood's 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.