This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skin lesions and disorders of pigmentation, Subject name: Dental
Topical azelaic acid is used in - 
Select and explain. 
A. Hyperpigmentary disorders, B. Dermatophvte infections, C. Vitiligo, D. Mixed infections
A: Hyperpigmentary disorders
Answer: A: Hyperpigmentary disorders 
Explanation: Topical azelic acid is used in treatment of melasma a hyper pigmentation disorder. azeliac acid is a competitive tyrosinase inhibitor that inhibit the synthesis of melanin. It is used as 10-20% cream and is as efficacious as hydroquinone. IADVL textbook of dermatology , pigmentary disorders page 750