Doctors Discover Four Autoimmune Diseases in One Woman After Unexplained Anemia

A 40-year-old woman in China has been diagnosed with four separate autoimmune diseases at the same time, offering doctors a rare glimpse into how misfiring immune systems can attack multiple organs. The unusual case was described in Frontiers in Immunology.

The patient was already known to have three conditions affecting her liver, bile ducts and large intestine. When she developed severe iron deficiency anemia without any obvious source of blood loss, clinicians began searching for another explanation.

Unexplained anemia triggers new search

Blood tests showed her hemoglobin had dropped to 89 grams per liter, well below normal levels. Repeated stool tests found no hidden blood, and a gynecological examination ruled out menstrual or reproductive tract bleeding.

With blood loss unlikely, doctors suspected her body might not be absorbing iron properly. They turned their attention to the upper digestive tract, where iron is first processed for absorption in the small intestine.

Fourth autoimmune disease identified

An examination of the woman’s stomach revealed that part of the inner lining was severely thinned and inflamed. Microscopic analysis showed immune cells infiltrating the tissue and damage to parietal cells, which produce stomach acid.

Blood tests also detected antibodies directed against these parietal cells. Taken together, the findings confirmed autoimmune gastritis, a disease in which the immune system attacks the acid-producing cells of the stomach.

Stomach acid is crucial for converting dietary iron into a form that can be absorbed. When acid levels fall, even a normal iron intake may not be enough, leading to iron deficiency anemia like the one seen in this patient.

Complex overlap of digestive diseases

Before the new diagnosis, the woman had three other autoimmune conditions. One was ulcerative colitis, which causes chronic inflammation of the large intestine and can lead to abdominal pain, diarrhea and rectal bleeding.

She also had autoimmune hepatitis, in which the immune system attacks the liver, and primary sclerosing cholangitis, a disease that scars and narrows the bile ducts that carry bile from the liver to the intestine. Bile is needed to digest fats and absorb fat-soluble vitamins.

At the time doctors investigated her anemia, her ulcerative colitis was in remission, making intestinal bleeding much less likely. That strengthened the case that poor iron absorption, rather than blood loss, was the main problem.

Possible link to rare syndrome?

The cluster of autoimmune conditions resembled a rare disorder known as autoimmune polyglandular syndrome type 3B, or APS-3B. This syndrome typically involves autoimmune thyroid disease along with autoimmune conditions that affect the digestive system.

The woman did have hypothyroidism, a condition in which the body does not produce enough thyroid hormone. However, her thyroid gland had been surgically removed because of thyroid cancer, and doctors lacked clear evidence that it had been damaged by autoimmunity beforehand.

Because there was no proof of autoimmune thyroid disease, the clinicians concluded that the case mimicked APS-3B but did not meet all the criteria needed to confirm the syndrome. Even so, it highlighted how groups of autoimmune diseases can cluster in a single person.

Warning signs and future risks

Autoimmune gastritis is known to reduce absorption of both iron and vitamin B12 over time. In this patient, vitamin B12 levels were still normal, which matches previous research suggesting that iron deficiency can appear earlier than B12 deficiency.

The doctors prescribed iron supplements and planned regular monitoring of her vitamin B12 and folate levels. They also scheduled a follow-up stomach endoscopy with biopsies within 1–2 years because long-standing autoimmune gastritis can increase the risk of certain stomach tumors.

The authors of the case report stressed that multiple autoimmune conditions in one patient should prompt doctors to consider autoimmune polyglandular syndromes. They also emphasized that unexplained iron deficiency is not always due to diet or hidden bleeding and may signal additional autoimmune damage.

Experts note that cases like this remain rare, although people with one autoimmune disease are known to have a higher risk of developing others. Large studies suggest that women are disproportionately affected by autoimmune conditions, likely due to a mix of genetic, hormonal and environmental factors.

Because this report describes only a single patient, it cannot reveal how often such combinations occur or whether one disease triggered the others. Still, it underscores the need for comprehensive evaluation in complex autoimmune cases and careful long-term follow-up.