A 17 years old girl with acne has been taking a drug for the last two years. She now presents with blue black pigmentation of nails. The likely medication causing the above pigmention is –

Patients taking minocycline may develop a diffuse blue - grey, muddy appearance in sun exposed areas in addition to pigmentation of mucus membranes, teeth, nails, bones and thyroid. Amongst tetracyclines two side effects unique to minocycline are drug induced lupus and blue black pigmentation.