This 58 yr old lady developed ecchymosis progressively increasing to present size for last 5 days on her arm , no h/o any trauma, not on any medications,  no other petechie or ecchymosis on any other part of body. Pt, aptt, Inr were wnl, FBS was more than 200 on two occasions, no polyuria polyphagia or polydipsia.

However ecchymosis resolved after inj vitamin k within 3 days what could be the cause for this?