A 12-year-old girl was brought to the doctor by her mother for a rash that developed on her upper body a few months prior. The rash worsened the weekend prior after a beach vacation where she was exposed to considerable heat and sunlight. Her mother wondered if this was a sunburn. On examination, reddish and brown, scaly and eroded plaques were seen on the neck and in the axillae. She was otherwise well and had no systemic symptoms. The patient’s mother noted that her husband and father-in-law had similar rashes. What’s the diagnosis?