Peculiar pigmented patch

An 18-year- old girl complains of a peculiar brown patch on her right anterior thigh for 3 weeks. With bikini season around the corner she wants it gone! She does admit to leaning her laptop on her right thigh for a few hours each day. What's the diagnosis?

A one-sided story

An anxious father schedules an urgent office visit for his 5-year-old boy who has a total body red bumpy rash. It started on the left flank 3 weeks ago and is still most prominent in this area (fig. 1). The boy appears well and the rash is only minimally itchy. The father refuses to leave the office until you give him the answer. What’s the diagnosis?

See the spots

During a sports physical you note a localized area of brown spots on the right side of the abdomen and right leg of a healthy 14-year-old girl. Her mother tells you that this has been present since birth. Although you clear her for sports activities, you consider the implications of the pigmented lesions. What’s the diagnosis?

Out, out, damn'd spot!

You are called to the emergency room to calm some panicked parents who brought their healthy 2-year old boy in for evaluation of black spots on his legs which were noted when he awoke this morning (fig. 1). It seems that his younger brother developed similar black spots later this morning. The boys are healthy and the lesions are not symptomatic. What’s the diagnosis?