The 5-year-old boy lay in his grandmother’s arms. “My feet, my feet,” he wailed. She smoothed the tangled bangs away from his forehead then reached for her phone. She wasn’t sure what was going on with her grandson, but she had cared for enough children and grandchildren to know that something was really wrong. His feet were swollen and painful and so were his hands. On his legs there was a rash that exploded over the several hours he was at her house into a series of raised red rings. She called her son and daughter-in-law. The little boy needed to go to the hospital.

He’d always been delicate, his mother explained to the triage nurse at the E.R. of Lowell General Hospital in Lowell, Mass. If one of his brothers had a runny nose, he’d get a runny nose and a fever. He was sick so often that she’d once taken him to the pediatrician to see if there was anything wrong with his immune system. The pediatrician assured her that it was a typical response to starting kindergarten, when first-time students would catch all the viruses going around. Just the previous week he had an awful cold. But he’d never had anything like this.

It started with a stomachache the night before. The boy was up for hours. Then in the early morning, when his father took him to the bathroom, he noticed that the tip of the boy’s penis was red and inflamed. As soon as his wife awakened, he told her about the situation and took him to the hospital.

The child was seen right away. He didn’t have a fever and was drinking well, though reluctant to eat. He said he didn’t have a stomachache anymore, and his belly wasn’t tender. His penis, though inflamed, didn’t seem to hurt, either. But his white-blood-cell count was elevated, and that suggested the child had an infection. The E.R. doctor figured he probably had balanitis, an infection of the head of the penis, and gave him a week of an oral antibiotic.

When the boy was discharged from the hospital late that morning, the father called the boy’s grandmother. Could she look after him? He and his wife had to work, and the child and his grandmother were very close.

When they arrived at the home of his Lela — that’s how the boy pronounced abuela, the Spanish word for grandmother — he didn’t want to walk. He held up his arms in that familiar wordless plea: Carry me. When his father picked him up and took him to his grandmother, she received him happily, and he snuggled into her arms.

He slept for much of the afternoon but ate and played when he was awake. In the evening, the boy seemed feverish — hot and uncomfortable. His grandmother gave him a bath. As she washed him, she saw what looked like a couple of bites on his legs. When it was time to get out of the tub, he refused to stand up. He said his feet hurt. And when his abuela looked, his feet were puffy. His hands, too, seemed larger than normal, as if they had been blown up like balloons. Even his face looked swollen — his eyelids were distended, and his lips seemed enormous. And what she thought were bites were now strange red lines that snaked around his legs onto his thighs and belly. She called her daughter-in-law. Something’s not right, she told her. He needs to go back to the hospital.

The mother left work and hurried to her mother-in-law’s house. To her maternal eye, her little boy looked like a monster — he was so strangely swollen.

Credit…Photo illustration by Ina Jang

She snapped him into his car seat and sped off to the hospital. She carried the boy to the front desk; she was worried that the swelling of his lips could extend and cut off his airway, she told the triage nurse. The nurse was concerned, too, and they quickly took him into the busy emergency room.

The child was cranky and didn’t want to be examined. Both of his feet were obviously swollen. So were his hands and face. He cried when anyone tried to move his hands and feet. And he had this itchy, spreading rash. The E.R. doctor worried about a rare but potentially dangerous disease of the smallest blood vessels called Henoch-Schönlein Purpura (H.S.P.). (It has recently been renamed IgA vasculitis.) An autoimmune disorder, it primarily affects children and is characterized by a triad of symptoms: abdominal pain, arthritis and a rash.

The rash is caused by the affected vessels leaking blood into the surrounding tissues. When this happens close to the surface of the skin, it creates dark red or bruise-colored spots. When these lesions are pressed, they don’t change color. But the boy’s rash was a light, not dark color, and when touched those spots lost the pink coloring and became pale. H.S.P. also causes a rise in inflammatory markers in the blood, so the doctor ordered a test to look for that as well. Those markers were slightly elevated, and so to be safe, the E.R. doctor decided to admit the child to the hospital to be monitored overnight. She ordered ibuprofen for the pain and an antihistamine for the itch.

The next morning, the boy was seen by Dr. Krista Birnie, a pediatric hospitalist. By then he looked more comfortable, though he still didn’t want anyone to touch his swollen hands or feet. It probably wasn’t H.S.P., Birnie decided, now that she saw the child. Although the boy didn’t want to move his hands or feet, it looked to her as if that was because of the swelling rather than some form of arthritis, a symptom of H.S.P. And the pink circles of rash had not turned into the angry red blotches characteristic of H.S.P.

The child’s parents reported that the rash started out looking like hives, which then grew into expanding circles and faded away — only to be replaced by others. The E.R. doctor had also ordered a test for Lyme disease. There was a field behind the boy’s house where he often played, and it could harbor deer ticks. Birnie didn’t think this looked like the typical Lyme rash, though Lyme disease was a common infection in northern Massachusetts.

Birnie was thinking along different lines. This child had first come into the hospital with a lesion on his penis. Just 12 hours later that lesion was gone. And the boy’s parents noted that his lesions were transient like hives. There was a disorder Birnie had heard of but never seen called Urticaria multiforme (U.M.). It’s a type of allergic reaction, she remembered, seen in kids usually after a viral infection, but Birnie couldn’t recall more than that. After her rounds, she found a computer and looked up the disorder. The description fit this child perfectly. It’s an allergic response triggered by either a medication or more commonly a viral infection. This child had a cold the week before.

The allergic reaction causes a release of histamine, a body chemical that causes (among other things) plasma to leak out of blood vessels, causing hives and the characteristic swelling of the feet, hands and face. It is usually treated with antihistamines — to block the histamine. The boy had an antihistamine on admission because he felt itchy. There’s no test for Urticaria multiforme, but given his symptoms, Birnie felt confident he had it. Still, she wanted to watch him one more day.

The next morning the child was a little less swollen, though he continued to get new hives. The Lyme test hadn’t come back, but Birnie was pretty sure that when it did, it would be negative. The child had a follow-up appointment with his primary doctor a couple of days later. Birnie called a few days after that to make sure the boy was feeling better. He was. And she was right — the Lyme test was in fact negative.

To the boy’s mother, this was just one more illness experienced by her delicate child. But it made an impression on him. Three years later, when he sometimes tells his mother that his feet hurt, she knows that means he’s feeling sick.