An autoimmune diagnosis in childhood may not be the end of the story. A nationwide Norwegian study found that some children with celiac disease, type-1 diabetes, or another autoimmune condition later developed a second one. The pattern also varied depending on where in the country they lived.
Researchers estimated that 2.6% of children would develop at least one of six autoimmune diseases by age 18. Among affected young people who had reached 18, about 8% had at least one additional condition.
When immune defense turns inward
An autoimmune disease begins when the immune system, which normally fights infections, mistakes healthy cells for a threat. The attack can damage the intestines, hormone-producing organs, joints, liver, or nervous system.
The diseases feel different in daily life. Celiac disease makes gluten trigger immune damage in the small intestine, type-1 diabetes destroys insulin-producing cells, and inflammatory bowel disease causes lasting inflammation in the digestive tract and includes Crohn’s disease and ulcerative colitis.
What the team tracked
Ketil Størdal of the University of Oslo and Oslo University Hospital led the work with Runar Almaas, Helga Sanner, Line Sletner, and Lars Christian Stene. He framed the central question plainly, saying, “We are trying to understand why more children are getting these diseases now than before.”
The complete analysis included 793,772 children born from 2007 through 2019. The team linked four national databases and required at least two separate diagnostic records before counting a case.
It tracked celiac disease, type-1 diabetes, inflammatory bowel disease, autoimmune thyroid disease, juvenile arthritis, and autoimmune liver disease.
Celiac disease led the list
Celiac disease was the most common diagnosis, followed by type-1 diabetes and autoimmune thyroid disease. Across all six conditions, the age-18 estimate works out to roughly one child in 38.
Earlier work points in the same direction. A 2017 Norwegian study described a rapid rise in pediatric celiac disease, while a 2025 regional analysis reported increasing inflammatory bowel disease among children in southeastern Norway.
A separate global modeling paper also highlighted the growing burden of type-1 diabetes in children and teens.
One diagnosis can signal another
Across the full follow-up period, 709 children received two or three distinct autoimmune diagnoses, about 5% of those with an autoimmune disease. Among affected participants followed through age 18, the share was about 8%.
The overlap was especially high in the small group with autoimmune liver disease. Of 157 children with that diagnosis, 65, or about 41%, developed another autoimmune condition.
Not every pairing appeared. Inflammatory bowel disease did not show significant co-occurrence with type-1 diabetes or autoimmune thyroid disease. For a family already managing insulin at breakfast or checking every school lunch for gluten, the message is to pay attention, not panic.
A north-south pattern emerged
After accounting for other measured differences, northern children had rates 83% higher for juvenile arthritis, 52% higher for inflammatory bowel disease, and 14% higher for type-1 diabetes than children in southern Norway. This pattern did not apply to every autoimmune condition.
A map can reveal a clue, but not a cause. The study cannot show that living in the north triggers autoimmune disease, it merely identifies a geographic association that researchers can now investigate.
Genes are only part of the puzzle
So what could geography be picking up? Researchers are comparing genetic data to see whether inherited vulnerability differs by region. Genetics may explain part of the pattern, but the team does not expect it to explain everything.
They are also studying diet, antibiotic use, and whether children grow up near nature or in more heavily built urban surroundings. Those factors may shape immune development, but the current study does not prove that any one of them caused disease.
Vitamin D seemed like an obvious possibility because sunlight varies sharply across Norway. Yet earlier work by the group suggests it is unlikely to explain the regional differences on its own.
What families and doctors should know
Most children with one autoimmune disease did not develop another by age 18, so new and persistent symptoms should not automatically be blamed on the original diagnosis.
The finding does not mean every child needs every test. Doctors may need a lower threshold for checking a related condition when symptoms fit, such as new intestinal or liver problems in a child with juvenile arthritis.
“We must pay close attention,” the lead researcher said, especially when symptoms point beyond the first diagnosis.
Coordinated care matters, too. A shared plan can keep families from bouncing between specialists whose treatments and follow-up schedules do not fully connect.
What the study does not prove
The research does not establish why some childhood autoimmune diseases have become more common, and its regional pattern may differ elsewhere. Because it relies on recorded diagnoses, differences in testing or health care use could also influence the data.
Still, the nearly nationwide coverage makes this an unusually strong snapshot. It turns a broad rise in childhood illness into specific questions about shared biology, place, and medical follow-up.
The official study was published in The Lancet Child & Adolescent Health.
