The NEJM recently published a case report in their “Images in Clinical Medicine” section describing the development of greyish-blue skin discolouration due to minocycline.

Drugdex cites several reports of minocycline-associated skin hyperpigmentation. This skin pigmentation has four presentations:

• Type I: most common, blue-black discoloration in areas of scarring and inflammation
• Type II: blue-grey pigmentation of legs and forearms of previously normal skin
• Type III: least common, muddy-brown discoloration in sun-exposed areas
• Type IV: occurs in pre-existing scars and is not limited to sun-exposed areas.

Discolouration can take months to years to resolve after discontinuing the drug.  Some of NEJM’s content including “Images in Clinical Medicine” can be accessed for free after registering as a user. You can read the full case report here.