The rash first appeared three months before, in July, the child's mother told Nadoolman, a pediatrician based in Berkeley, Calif. And it had returned every couple of weeks since. It always started around 4 a.m. Her son would wake her up crying and tell her that he was getting the rash. At that point, it didn't look like much — the skin around the boy's mouth, nose and eyes would be pink and a little puffy. But by morning, the skin on the entire lower half of his face would be red and swollen and as angry-looking as a slap. The same irritated red rash appeared on the skin of his penis as well. A day later, the skin would start to crack and peel. Finally, after a couple of days, the swelling and redness would start to recede, and by Day 4 or 5, he'd be back to normal — until the next time.
And, his mother added, everything seemed to have become worse over the past month or so. He started nursery school just after Labor Day, and since then the outbreaks had become more frequent.
Nadoolman turned to the child. Does the rash ever hurt inside your mouth? he asked the boy. No. Inside your nose? No. Does it itch? No. Does it hurt when you pee? No. Does it hurt when you talk or eat? The boy nodded his head sadly.
A few weeks earlier the child had his most severe attack, the mother told the doctor. His entire face was red and puffy. Even his eyelids were swollen. She was worried. Because the family had recently moved to Berkeley and hadn't yet found a pediatrician, she called the emergency room at the local hospital. The nurse there suggested that it could be a food allergy. She recommended Benadryl. She could bring in the child, but it would be a wait. The mother started calling pediatricians. After several attempts, she found one who could see her son that day. That doctor made his diagnosis almost as soon as he saw the boy: poison oak. Impossible, the mother responded. The only plants he had any contact with were in his grandmother's backyard vegetable garden. She weeded it religiously. There was definitely no poison oak there. That doctor called in his partner for a quick second opinion. As soon as he laid eyes on the child, he pronounced his diagnosis: poison oak, he echoed. The mother sighed. She was sure it wasn't poison oak, she told Nadoolman. What else could it be?
Nadoolman was challenged by the idea of diagnosing a rash he had not seen. Although a patient's story usually provides the most important clues to diagnosis, when it comes to lesions of the skin, visual recognition is a doctor's most powerful tool. Dermatologists in training are tested on their ability to identify a skin finding without ever touching or even talking to the patient. Seeing, they are often told, is everything. So could you make a diagnosis using only the story? Maybe. Nadoolman already had the basic history. Now he would have to dig a little deeper.
He turned to the child's mother. Were the boy's lips ever swollen, the doctor asked, or was the swelling limited to the skin around his lips? This was an important distinction, he explained. Two very severe forms of allergic reaction — angioedema and Stevens-Johnson syndrome — cause swelling of the mucus membranes and lips. If his lips were never involved, it might still be an allergic reaction but probably not one of these life-threatening ones.
The mother thought for a moment. It's not something she had paid attention to, but no, she was pretty sure that the lips themselves were never swollen. It was the skin around them that got so red and painful.
A rash limited to the face and the genitals is not uncommon in pediatrics and suggests that, whatever the cause, the most likely vector, at least in a small boy, was his own hand. "It is classic in poison oak and ivy," Nadoolman told me later. "And I suspect that's why the first pediatricians thought that's what this was." Poison oak can cause an irritating rash, known as a contact dermatitis. The hands are often spared in these kids probably because they are washed more frequently than the regions of the body they touch the most. In addition, the skin on the palms is thicker and more resistant to the allergen.
But the boy and his mom said that the rash wasn't itchy and didn't have the blisters seen in classic poison oak. Moreover, the mother seemed certain that her son had no contact with these plants. They did have a pet though, an American Eskimo dog. Could his long, thick fur be the vector bringing the urushiol — the "poison" in poison oak and ivy — home to the little boy?
The child spent a couple of afternoons a week in the backyard, gardening with his grandmother. They grew strawberries, pumpkin, squash, zucchini, cucumber, tomatoes and lettuce. Could it be something in the garden?
Another possible clue: the rash appeared only after the family moved to Berkeley. Was it something in the new house? And why did the rash appear more frequently after the boy started nursery school? Was there more of whatever it was at the school than at the home?
By the end of the visit, Nadoolman still wasn't sure what this was. Come back in two weeks, he told the pair, and he would try to have an answer for them. The doctor was still pondering the mysterious rash as he drove home. He spotted a small gardening store he passed every day. Maybe he should get a consult, he thought, as he turned into the parking lot. Maybe he was missing something. In medicine, what you don't know really can hurt you.
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http://www.nytimes.com/2010/10/17/magazine/17FOB-Diagnosis-t.html?pagewanted=print
