Type 1 diabetes mellitus (T1D), also called autoimmune diabetes mellitus, is an autoimmune disease. The immune system destroys the insulin-producing beta cells of the pancreas, so insulin secretion fails. Blood glucose then rises, because insulin is what moves glucose into cells.
Why is it a process, not an event?
The definition names the attack, but not how long it takes, and that timing is what the rest of the picture depends on.
Susceptibility to T1D is inherited. Something in the environment sets the autoimmune attack going. Beta cells are then lost in steps, over months to years. Clinical disease appears only when beta-cell loss is far advanced, so the process runs silently for a long time before the first symptom.
That is the organising idea: T1D is a process rather than a sudden event. Because the cells are lost in steps, and the immune attack leaves a trace in the blood well before any symptom, the process can be followed while the person is still well. That is why T1D can be detected before any symptoms, and why it is staged. It also explains why insulin replacement is needed for life once T1D appears.
Which note answers which question?
Once the process is clear, each part of it has its own note.
- Epidemiology and burden of type 1 diabetes: how common the disease is, how its incidence is changing, who is diagnosed and when, and what it costs the person and family.
- Environmental and early-life factors in type 1 diabetes: the early-life exposures, including nutrition, microbial contact and infections, that may influence whether the disease develops.
- Pathogenesis of type 1 diabetes: how family history and high-risk HLA genotypes make a person susceptible, and how environmental factors then drive damage to the beta cells.
- Natural history and staging of type 1 diabetes: the stepwise course of beta-cell loss before symptoms, the autoantibodies that mark and predict it, and the staging model.
- Screening for type 1 diabetes: how autoantibodies detect islet autoimmunity before clinical disease, and where screening programs stand.
- Presentation of type 1 diabetes: the symptoms of hyperglycemia, the ages at which the disease begins, and how ketoacidosis can be the first appearance of T1D.
- Diagnosis of type 1 diabetes: how islet autoantibodies, C-peptide and the clinical picture separate T1D from type 2 diabetes and from the slower adult form.
- Treatment of type 1 diabetes: insulin replacement with basal-bolus regimens, glucose monitoring, and the trade-off between control and hypoglycemia.
- Complications of type 1 diabetes: the acute emergencies, the microvascular and macrovascular damage, the associated autoimmune conditions, and the determinants of long-term outcome.
Where do I start?
Each part answers the question the one before leaves open. Start with Epidemiology and burden of type 1 diabetes, which asks how common the disease is and whether that is changing.