This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
A patient presents with erythematous scaly lesions on extensor aspect of elbows and knee. The clinical diagnosis is got by – 
Select and explain. 
A. Auspitz sign, B. KOH smear, C. Tzanck smear, D. Skin biopsy
A: Auspitz sign
Answer: A: Auspitz sign 
Explanation: Erythematous scaly lesions on extensor aspect of elbow and knee favours the diagnosis of Psoriasis.
The clinical diagnosis of psoriasis can be made by demonstrating Auspitz sign.
It is a characteristic finding of psoriasis in which removal of scale leads to pinpoint bleeding.