A Hidden Immune Disorder Unmasked by Type 1 Diabetes and Arthritis

A 44-year-old woman came to her doctor with severe digestive problems—persistent diarrhea and abdominal swelling that had lasted over eight months. Imaging showed her intestines were blocked. But when doctors reviewed her full medical history, they noticed a troubling pattern: she had been diagnosed with type 1 diabetes and chronic thyroiditis as a child, and later developed rheumatoid arthritis. She also learned that her brother had died from unexplained diarrhea during childhood.

This combination of autoimmune diseases plus a concerning family history raised a critical question: Could all of these problems stem from a single genetic condition affecting how her immune system works?

Doctors suspected a primary immune deficiency—a genetic condition that causes the immune system to malfunction. Genetic testing revealed the answer: the woman had LRBA deficiency, a rare inborn error of immunity. LRBA stands for lipopolysaccharide-responsive beige-like anchor protein, and it plays an important role in controlling immune responses.

The woman carried two different genetic variants in her LRBA gene—one a splice-site mutation and another involving a deletion of multiple gene segments. This compound heterozygous pattern means she inherited different genetic problems from each parent, and together they disrupted normal LRBA function.

LRBA deficiency is characterized by immune dysregulation, meaning the immune system cannot properly control itself. This dysregulation often leads to autoimmune diseases, where the immune system attacks the body's own tissues. In this case, it had triggered type 1 diabetes, thyroiditis, arthritis, and severe intestinal problems.

When the woman began treatment with abatacept—a medication that helps regulate immune function—doctors measured several inflammatory proteins in her blood to understand what was happening at the molecular level. Abatacept is a CTLA4-immunoglobulin fusion protein that helps calm overactive immune responses.

After treatment, the levels of three key inflammatory markers decreased significantly: interleukin-17A, tumor necrosis factor, and a chemokine called CCL20. These are proteins that drive inflammation and autoimmune activation. As these markers fell, her gastrointestinal symptoms improved, suggesting that controlling the underlying immune dysregulation helped relieve her digestive problems.

This case demonstrates an important clinical lesson: when someone has multiple autoimmune diseases—especially starting in childhood, with a family history of similar problems—a primary immune disorder should be considered. Type 1 diabetes, rheumatoid arthritis, and thyroiditis are each common on their own, but when they cluster together with severe digestive issues and genetic clues, they may reflect a single underlying genetic condition rather than separate coincidental diseases.

Identifying LRBA deficiency changed this woman's treatment path. Instead of managing each autoimmune disease separately, doctors could target the root immune dysregulation with abatacept, which proved beneficial for her gastrointestinal symptoms. For families with multiple autoimmune diseases, genetic testing and consultation with immunologists may uncover treatable underlying conditions.

Source: Journal of clinical immunology. Evidence type: PubMed indexed literature. Type1Cure is an information and intelligence hub, not a medical advice service. This article summarizes published research and does not provide diagnosis, treatment, or personal medical guidance. Always talk to your own care team before changing anything about your Type 1 diabetes management.