Autoimmune diseases and autoimmune polyglandular syndromes in adult patients with biopsy-confirmed celiac disease

Celiac disease (CD) is an immune-mediated disorder frequently associated with autoimmune diseases (ADs) and nutritional deficiencies. This study aimed to determine the prevalence and spectrum of additional ADs and autoimmune polyglandular syndromes (APS), as well as micronutrient deficiencies, in adults with biopsy-confirmed CD. This prospective observational study included 102 adults with previously diagnosed, biopsy-confirmed CD who were under regular outpatient follow-up. Demographic and clinical characteristics, additional ADs, APS subtypes, laboratory parameters, micronutrient deficiencies, and adherence to a gluten-free diet assessed using the celiac dietary adherence test (CDAT) were evaluated. Additional ADs were identified in 26 of 102 patients (25.5%; 95% confidence interval [CI], 18.0–34.7), with autoimmune thyroiditis being the most frequent (12.7%; 95% CI, 7.6–20.6). APS was identified in 16 patients (15.7%; 95% CI, 9.9–24.0). APS type 3 was the most frequent subtype (11.8%; 95% CI, 6.9–19.4), followed by APS type 4 (2.0%; 95% CI, 0.5–6.9), whereas APS types 1 and 2 were each identified in 1.0% (95% CI, 0.2–5.3). At least 1 micronutrient deficiency was present in 93.1% (95% CI, 86.5–96.6), and 54.9% (95% CI, 45.2–64.2) had 2 or more deficiencies. Vitamin D deficiency was the most common (90.2%; 95% CI, 82.9–94.6), followed by folate deficiency (33.3%; 95% CI, 24.9–42.9), iron deficiency (29.4%; 95% CI, 21.4–38.9), vitamin B12 deficiency (17.6%; 95% CI, 11.5–26.2), and iron deficiency anemia (17.6%; 95% CI, 11.5–26.2). Patients with poor gluten-free diet adherence had significantly higher frequencies of 2 or more micronutrient deficiencies, folate deficiency, iron deficiency, vitamin B12 deficiency, and iron deficiency anemia than those with good adherence. Adults with established CD under follow-up had a substantial burden of additional ADs, defined APS phenotypes, and micronutrient deficiencies. Autoimmune thyroiditis and APS type 3 were the predominant autoimmune manifestations. Micronutrient deficiencies remained frequent even among patients with good self-reported gluten-free diet adherence, supporting continued nutritional monitoring during long-term follow-up.