The test likely to help in diagnosis of a patient who presents with an itchy annular plaque on the face is –: (A) Gram's stain, (B) Potassium hydroxide mount, (C) Tissue smear, (D) Wood's lamp examination
Answer is B. The clinical picture is suggestive of a fungal infection most likely Tinea fascitis, KOH preparation is performed on scaling skin lesion when fungal etiology is suspected. Microscope examination after KOH digestion will show fungal hyphae.