Curvilinear, erythematous plantar patch in a toddler

A healthy 2-year-old Caucasian boy was seen in the pediatric dermatology clinic during winter for a 4-day history of a painful red line on his right sole. At symptom onset, the patient complained of pain with ambulation. On the following day, his mother noted a curved red line on the right mid-lateral plantar foot (Figure 1) that was observed on subsequent days to have traveled toward his lateral toes (Figure 2). The patient had no pruritus, no preceding symptoms, no recent travel outside of Massachusetts, and no exposure to sand or soil. Family history was negative for similar symptoms. The patient’s mother attempted to extract the contents of the lesion unsuccessfully, causing an abrasion. On examination, a curvilinear, erythematous patch was noted on the right mid-lateral plantar foot without surrounding inflammation. The patch was slightly tender to palpation, and pain was elicited on ambulation, with subsequent refusal to bear weight. Dermoscopic examination was significant for a central, superficial dark line less than 1 mm wide and approximately 3 cm long at the leading edge of the lesion. The remainder of his skin examination was normal.