Medical mystery: Why was this boy so short?

Why is he so tired, Jackie Mann wondered, not for the first time, as Evan, the middle of her three children, wandered off to his bedroom to take an after-school nap.

Small for his age, the 12-year-old seemed to fall asleep easily and anywhere.

But his parents noticed that Evan seemed decidedly more energetic on the weekends in the semirural community outside Oakland, Calif., where the family lives. Then he went fishing, hunting and hiking with little difficulty.

"We just kind of thought he was faking it," said Mann.

But Mann's concerns intensified after a trip to Lake Tahoe. Evan, an avid skier, would complete a run or two, complain that he was tired, and go back to the cabin to sleep for several hours.

For 18 months, as Evan's fatigue worsened, his growth stalled and he wrestled with unexplained low-grade fevers and joint pain, a series of doctors sought to figure out what was making him sick.

When Evan was in fifth grade, his mother began asking the pediatrician about his unusually small size. But the doctor pointed out that all of her children were small, her husband is 5-foot-6 and Mann is 5-3.

In the spring of 2011, Mann decided to switch doctors, fearing that her concerns weren't being taken seriously. At the time Evan weighed 63 pounds and was 4-4, seven inches shorter and 25 pounds lighter than average for a boy his age.

She also found an allergist to determine whether Evan's frequent sinus infections were the result of allergies that might be impeding his growth and causing his fatigue. As a child, he had taken antibiotics frequently for ear infections, and he was often prescribed the drugs for sinusitis as he got older. But the work-up found no allergies.

A few months later, Evan visited his new pediatrician, who was concerned, particularly after he plotted a growth chart, which showed that Evan hadn't grown in at least two years.

Shortly after that visit, Evan developed a bad case of hives and was prescribed several weeks of prednisone, a corticosteroid used to suppress inflammation. The change was dramatic: His energy level and appetite ticked up.

But when school started and Evan stopped taking steroids, the fatigue returned.

During a hike with relatives, one of whom is an internist, Mann confided her fear that Evan had recurring fevers or Lyme disease. The relative was skeptical, but advised her to keep a record of Evan's temperature, along with a symptom diary.

Mann did, and noticed a pattern. Evan's fatigue seemed to descend every third day or so. On those afternoons, he had a fever of about 101 degrees and often complained of a headache and achy joints. Some days he also had mild diarrhea.

"Saying there was a measurable fever got everyone's attention," Mann recalled. When she showed the temperature and symptom chart to the new pediatrician, he immediately referred Evan to a specialist in pediatric infectious diseases.

Evan's hives, fevers and fatigue seemed to suggest an environmental cause. But extensive testing ruled out many zoonotic exposures (diseases that can be transmitted from animals to people) including Lyme and hantavirus, as well as other infections.

The infectious-disease specialist referred Evan to a pediatric gastroenterologist.

During the initial appointment Jan. 10, 2012, the GI specialist looked at Evan's fingers and at the cold sores that seemed ­ever-present on the corners of his mouth, and he felt the boy's abdomen. Within 10 minutes, he turned to Evan's parents.

"Your son has Crohn's disease," Mann remembers him announcing. "I'm sure of it."

Mann and her husband were shocked — and skeptical. Crohn's, a serious, chronic and incurable autoimmune disorder characterized by severe abdominal cramps and diarrhea, seemed unlikely to them. Evan had only occasional, mild diarrhea.

"How can you be so sure?" Mann remembers asking. The doctor ticked off the telltale signs: Evan's growth was stunted. He had chronic cold cores on the corners of his mouth, a common Crohn's symptom. The ends of his fingers were clubbed. When he pressed on Evan's lower right abdomen, the boy felt pain. Several tests had indicated unusually high levels of inflammation. Evan had greatly improved while taking steroids, a mainstay treatment for Crohn's.

There was a family history: Evan's great-grandmother and another relative had been diagnosed with Crohn's, and another close relative had a similar disorder, ulcerative colitis. Evan also had taken a lot of antibiotics at a young age, which can raise the risk of Crohn's. And finally, the Manns are Ashkenazi Jews, whose descendants came from Central and Eastern Europe; Crohn's is more common among Ashkenazi Jews than in the general population. Scientists have recently discovered several genetic mutations among Ashkenazi Jews that raise the risk of Crohn's.

The disease, which is believed to result from an interplay between genetics and the environment, can look different in children and adolescents, said Sabina Ali, a pediatric gastroenterologist who has treated Evan since 2013. Pediatric patients sometimes don't have the classic symptoms seen in adults with Crohn's — chiefly, severe cramps and frequent diarrhea — which can mislead doctors.

"Evan had extra-intestinal symptoms," Ali noted, adding that extreme fatigue is not common and may point to a second, as yet unidentified problem. "These kids can get sidetracked into other specialties because no one realizes they have a GI problem." In addition "some of these kids may get frequent illnesses or fevers," the latter of which are regarded as signs of infection but actually are signals of inflammation.

An endoscopy and a colonoscopy confirmed the diagnosis. Because of the severity of Evan's disease, doctors recommended surgery to remove sections of his inflamed intestines.

Since his 2014 surgery, Evan has received regular infusions of Remicade, a drug commonly used to manage Crohn's. He takes vitamins to counteract nutritional deficiencies.

Now 17, he has grown significantly and is, his mother says, "the healthiest he has been in years." At 5-6, one inch shorter than his older brother, he weighs 122 pounds. He is in his senior year of high school and hopes to attend a California university to study watershed management.

After Evan was diagnosed with Crohn's, his sister was evaluated for the disease. Although healthy, her parents were concerned that her small size might reflect an underlying digestive problem.

"She doesn't have the disease at this time," Mann said of her daughter, who is now 15. "At 4-9, she's just plain short."