Pescatarian

A 3 year old is brought in for dry, scaling skin. Interestingly, the father has this skin problem too, though it has been undiagnosed. "I always thought it was just atopic dermatitis," he says. The father says that his got significantly worse at puberty. It becomes worse with dry weather and is especially pronounced in winter. Most of the lesions are on the shins, back, and heels. They do not occur in flexural areas.

Challenge: What do father and son have?

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