<prompt> A child has been brought with the following scalp lesion with history of itching in scalp and hair loss for past 2 months. Which of the following is useful for diagnosis of this patient?Gram stainKOH mountSlit Skin smearTzanck smear  <response>: Ans. B KOH mountRef: Fitzpatricks Dermatology, 8th ed. pg. 2284-85The image shows black dot sign classical of tinea capitis. The hairs are damaged due to endothrix infection and break easily. 