Hi
This could be
diabetes dermopathy or shin spots. They appear as asymptomatic ,round , brown , slightly depressed patches. Old lesions resolve in 18-24 months and new lesions appear. Most common site is over shins.
The exact cause is not known but they may be associated with increased risk of microvascular complications.
Next Steps
get evaluated for proper glycemic control, diabetic retinopathy and nephropathy.