A 30-year-old woman rapidly developed an intensely pruritic eruption on both legs, that extended from the knees to the upper thighs. The eruption occurred 24 hours after she was pulling out weeds while kneeling in her garden.
Key point: The linear arrangement of the papulovesicular lesions, many of which were excoriated, generally indicates an acute allergic contact dermatitis. She was most likely kneeling in poison ivy, thus accounting for the limited distribution of the eruption.
Treatment: The patient was given a rapidly tapering (over 3 weeks) course of oral prednisone and advised to take diphenhydramine, as needed, to help alleviate itching.
Note: While many diseases can be linear, the history and symptom severity suggest the correct diagnosis and therapeutic approach.