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 male patient presents with patchy loss of hair on scalp, eyebrows and beard. He also gives history of rapid graying of hair in a few areas. The likely diagnosis is – 
Select and explain. 
A. Alopecia areata, B. Anagen effluvium, C. Telogen effluvium, D. Androgenic alopecia
A: Alopecia areata
Answer: A: Alopecia areata 
Explanation: Information provided in this question are -


Patchy hair loss (focal alopecia)
Hair loss on scalp, eyebrows and beard
Histor of rapid graying of hair


All suggest the diagnosis of Alopecia areata -


In Alopecia areata, hair loss is patchy and well circumcirbed.
Alopecia areata most commonly involves scalp but any hair bearing skin e.g., beard, eyebrows, and eye lashes can be involved.
The characteristic feature of alopecia areata is sparing of grey/white (non-pigmented) hair and preferential involvement of block/brown (pigmented) hair. If alopecia progress rapidly, it appears as rapid greying of hair as black hair are shed and grey hair are spared → Going gray/white overnight phenomenon.