Reversible dermal atrophy in a cat treated with phenytoin.

Phenytoin, given to a cat in proportions therapeutic for man (5 to 8 mg/kg), induced severe dermal atrophy with excessive fragility of the skin following daily oral administration for 3 weeks. Dermal collagen was depleted, but remaining collagen seemed structurally normal. Upon cessation of phenytoin treatment, the cat recovered. In an effort to establish an association between phenytoin treatment and a dermal collagen disorder, phenytoin treatment was repeated and the dermal lesion confirmed.