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Solve the Medical Riddle: She Had a Rash on Her Arms and Then New Patches Started Appearing on Her Legs, Second Week

Editor’s note: Welcome to our ThirdAge feature that gives you a chance to play medical sleuth as we share the details of what happened when a patient presented with a problem that stumped the physician at first.

Last week, the patient reported her symptoms to an Urgent Care doctor who referred her to a dermatologist. This week, the dermatologist will proceed with the examination using the first three components of the classic S-O-A-P notes, which is as follows:

S=Symptoms or Chief Complaint

O=Objective Findings

A=Assessment or Analysis

P=Treatment Plan or Recommendations


The third week, we’ll let you know what some people have suggested as possible diagnoses. The fourth week, the dermatologist will move on to P to reveal the actual diagnosis. Then we’ll begin a new riddle for the following month!]

S=Symptoms or Chief Complaint

The dermatologist took a subjective history from Cynthia, asking about any possible reason for the widespread rash. The itching was a clue that the problem was likely an allergic reaction of some type rather than an internal manifestation of a more serious condition such as  secondary syphilis, Lyme disease, a photosensitive drug eruption, or even chicken pox or shingles although shingles would be painful in presentation and limited to one side area of the body.

Cynthia told the dermatologist about her sword fern theory and the specialist agreed that was a possibility at least for the initial patches of rash, which were probably contact dermatitis. The fact that Cynthia did not get a rash the previous year after the first time she touched the ferns actually strengthened the doctor’s suspicion that Cynthia might be correct. That’s because contact dermatitis occurs after repeat exposure. It takes an initial exposure to sensitize the person to the allergen and develop the immunologic response.

The dermatologist went on to ask whether Cynthia had begun taking new medications but Cynthia said that wasn’t the case. The doctor then explored other possibilities including the fact that Cynthia’s hosts in Montana had bought new sheets and pillowcases for the guest bed that might have had formaldehyde in the fabric. The doctor also said Cynthia might be allergic to the kind of laundry detergent her hosts had used when washing sheets and towels. These seemed to be remote possibilities regarding the initial outbreak, though. The rash had only appeared on Cynthia’s arms and not on her cheek, which would have touched the new pillowcase, or on areas of her body that she would have dried with a laundered towel.


O=Objective Findings

The dermatologist examined Cynthia’s skin completely, including mucous membranes and nails. The mouth is a common place for blistering lesions caused by pemphigus, a rare but serious skin disorder, and nails can be involved in contact dermatitis.