A 25 yr old lady develops brown macular lesions over the bridge of nose and cheeks following exposure to sunlight. What is the most probable diagnosis?

This lady is showing features of chloasma which is a brownish macular hyperpigmentation of the face mostly over the cheek, forehead, nose, upper lip and chin. In a small percentage of cases it is also seen on the malar or mandibular areas of the face and occasionally the dorsum of the forearms. It is exacerbated by sunlight. This is usually seen in women during pregnancy, in women taking OCPs and living in sunny regions. It is also associated with the ingestion of diphenylhydantoin. Ref: Suurmond D. (2009). Section 13. Pigmentary Disorders. In D. Suurmond (Ed), Fitzpatrick's Color Atlas & Synopsis of Clinical Dermatology, 6e.