Type 1 diabetes mellitus (T1DM) is a chronic disease of insulin deficiency resulting in hyperglycemia. In the vast majority of cases, insulin deficiency follows immune-mediated destruction of pancreatic beta cells, resulting in underproduction of insulin and subsequent hyperglycemia. It most commonly presents in childhood (5-7 years of age) or adolescence but can present at any age. Of note, a significant number of cases of T1DM are diagnosed in adults. Diabetes manifests only after the destruction of a majority of pancreatic beta cells.

Patients with clinical T1DM often present with hyperglycemia, polyuria, and polydipsia as well as possible weight loss, fatigue, nocturnal enuresis, and blurry vision. Patients may show signs of a concurrent infectious illness such as a cough, fever, or other symptoms. T1DM patients may present with diabetic ketoacidosis (DKA), a state of severe dehydration and acidemia due to insulin deficiency. Symptoms include abdominal pain, nausea, emesis, inattention, confusion, and even coma in the setting of hyperglycemia and elevated anion gap. DKA is often associated with compensatory hyperventilation (Kussmaul respiration) in the setting of primary metabolic acidosis, with a fruity breath odor resulting from ketones created by fat breakdown.

The pathogenesis appears to be rooted in a genetic component that interacts with an environmental insult in most cases. The incidence of T1DM has been increasing in the United States over the last several decades, with 2-3 new cases per 10 000 person years. There have been several reports about increased incidence of T1DM following acute COVID-19 infections.

Genetic risks (HLA haplotype and other identified genes) for T1DM account for almost 40%-50% of cases. The anti-CD3 monoclonal antibody teplizumab-mzwv is approved by the US Food and Drug Administration (FDA) to delay the onset of clinical T1DM for genetic high-risk patients aged 8 years and older.

Related topics: bullosis diabeticorum, diabetes mellitus type 2, diabetic dermopathy, diabetic hyperosmolar syndrome, diabetic nephropathy, diabetic neuropathy, diabetic retinopathy, diabetic vulvitis, maturity-onset diabetes of the young (MODY), neurogenic ulcer