Type1Diabetes? Type2Diabetes? Or Double Diabetes?

Objective:To explore the classification diagnosis of the diabetes in order to get a better understanding of the differential diagnosis in diabetes.Methods:The history of disease, clinical manifestations and laboratory examinations of two atypical diabetes patients were presented in detail. Their potential classification diagnoses were discussed. At the meantime, we reviewed the literature by searching the database of Chinese scientific and technical journals、CBM、CNKI and Pubmed from1991until now.Results:Diabetes is a complex disease and is characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both. Diabetes is one of the most frequently seen chronic diseases in the whole populations. Diabetes is believed to be caused by both genetic factors and environmental factors. ADA delivered Standards of Medical Care in Diabetes-2012.The Standards recommended the classification of diabetes, using an aetiological approach based on assessment of autoimmunity and insulin resistance (IR), in which four aetiological subgroups were defined. The four subgroups are type1diabetes (T1D), type2diabetes (T2D), other specific types of diabetes and gestational diabetes mellitus (GDM). More than95%diabetes are T1D and T2D, so, they are the cores of differential diagnosis, carrying consistent arguments. Type1diabetes is believed to be a chronic autoimmune disorder in which destruction of βcell in the pancreatic islets of Langerhans results in insulin deficiency and hyperglycemia. Diagnosis of T1D is usually definited by following clinical features:1)age less than30yr at diagnosis;2) moderate or severe clinical manifestation, such as polyuria, polydipsia and polyphagia;3) non-obesity or weight loss at diagnosis;4) fasting or postprandial plasma C-peptide levels significantly decline even absence;5) prompt onset and progression;6) diabetic ketoacidosis (DKA) at any time, with or without abdominal pain, vomiting, Kussmaul respirations, lethargy, and dehydration;7)positive pancreatic auto-antibodies,GAD-65, IA-2, ICA, or ZnT8;8) therapy depends on insulin to survive. Type2diabetes (T2D) is the most common form of diabetes characterized by hyperglycemia, insulin resistance, and relative insulin deficiency. Lifestyle is believed to be essential for T2D. Compared with type1diabetes, patients of T2D usually perform a late onset, a relative mild clinical manifestation and a lower tendency of ketoacidosis. Obesity or overweight, hypertention and dyslipidemia etc. are common in patients of T2D. Fasting or postprandial plasma C-peptide levels usually show a normal pancreatic β-cells function. Moreover, absence of pancreatic auto-antibodies, such as GAD-65, IA-2, ICA, is vital for diagnosis of type2diabetes. It is determined by the inexistence of autoimmunity in the T2D pathogenesis. What is important is that insulin is not necessary for patients of T2D, and lifestyle modification plays a great role. Clinical features and the presence of autoantibodies to β-cell antigens are generally used by clinicians to define the two forms of diabetes. Clinicians play an important role in the diagnosis. It seems that differentiating between the types of diabetes is becoming increasingly challenging, and the boundary is becoming indistinct. For example, on age of onset:5-15%of adults suffer from T1D, while more children and adolescent are reported to have T2D, mostly associated with obesity; on course of disease:T2D may be first diagnosed with DKA, and patients of T1D could represent with no or mild clinical symptoms, especially in adult with positive autoantibodies; on pathophysiology:patients of T2D may present secondary autoimmunity in the course, and obesity and insulin resistance may attack patients of T1D. Strategies of diabetic classification are gradually improved.Conclusion:Identification of type1and type2diabetes is mainly dependent on the clinical manifestations and laboratory examinations. Evaluation of pancreatic β-cells function occupies an important position in the classification, identification and treatment options. Presence or absence of islet autoantibodies also helps a lot. The diagnosis of some patients are quite difficult. Type1diabetes, Type2diabetes, or double diabetes? There are many unknown areas to be discovered about diabetes.