An Autoimmune Double Take: A Surprising Cause of Diarrhea in a Young Adult with Type I Diabetes

Introduction: Type 1 Diabetes Mellitus (T1DM) involves immune-mediated damage of pancreatic beta cells and subsequent hyperglycemia, manifesting as: polyuria, polydipsia, polyphagia, and weight loss.
Unique health maintenance recommendations for children with longstanding T1DM include: annual foot and dilated ocular exams. Laboratory testing includes: quarterly Hemoglobin A1c (HgbA1c), annual creatinine, and urine albumin-to-creatinine ratio.
Patients with T1DM are at risk for developing other autoimmune conditions, most commonly thyroid or celiac disease. Thyroid antibody testing should be performed at diagnosis followed by annual Thyroid stimulation hormone testing. Celiac disease screening at diagnosis must include a tissue transglutaminase IgA and a total IgA, because selective IgA deficiency increases the risk for celiac disease.

Case Description: A previously healthy 20yo female with T1DM (diagnosed at age 10, last HgbA1c=7.8%) and history of anemia is referred to Pediatric gastroenterology for 2 months of nocturnal, non-bloody diarrhea, left lower quadrant pain, and nausea. Her review of systems was remarkable for normal daytime bowel movements. She also complained of headache and lower extremity pains with numbness for which she had been referred to neurology. The patient’s initial lab-workup was remarkable for a low total IgA of <6.7mg/dL (Table 1). The selective IgA deficiency and lower tract symptoms increased the gastroenterologist’s concern for Celiac disease or ulcerative colitis.
The patient underwent upper and lower endoscopy which was grossly unremarkable; histology revealed a pattern consistent with autoimmune gastritis.
Subsequent serum evaluation was remarkable for an elevated fasting gastrin level and elevated parietal cell antibody level without macrocytic anemia or vitamin B12 depletion.
The patient was subsequently initiated on B12 supplementation therapy with improvement in her symptoms.

Discussion: Autoimmune gastritis involves immune-mediated destruction of parietal cells in the stomach. This reduces intrinsic factor production which can lead to vitamin B12 deficiency and pernicious anemia and can result in neurologic symptoms: fatigue, headache, weakness; gastrointestinal symptoms: diarrhea, abdominal pain, dysphagia; or other system involvement.
Our patient did not meet typical criteria for pernicious anemia. A multi-disciplinary discussion between pediatric gastroenterology and neurology concluded that inflammation that can occur from autoimmune gastritis could potentially manifest as neuropathic symptoms from small nerve fiber injury prior to evidence of significant vitamin B12 depletion.
Patients with autoimmune gastritis warrant endoscopy surveillance every 3 years to monitor for development of intestinal metaplasia and progression to gastric carcinoids and adenocarcinoma. Clinicians should be aware of the lifelong risk for patients with T1DM to develop other autoimmune conditions.

Conclusion: This case illustrates the importance of high suspicion for and recognition of red flag findings in a child with known autoimmune disease. Following well-established health maintenance recommendations for individuals with T1DM ensures that common comorbidities will be detected. Vigilance and employing a multidisciplinary approach are essential to promptly detect rarer, but impactful associated conditions.