Diabetes mellitus (DM) is due to either defects in not producing enough insulin by the pancreatic -cells, or defects in insulin action on peripheral tissues. Type 1 diabetes (T1D) is the most common type in childhood, resulted from the autoimmunity directed at the pancre-atic -cells. T1D classically presents in lean children with an acute onset of polyuria, polydipsia, weight loss. We describe the case of a 14-year-old girl with acute onset of DM complicated with diabetic ketoacidosis, appendicitis and pancreatitis which was suspected of having T1D. However, regardless a suggestive patient’s phenotype at the disease onset tentative diagnosis of T1D was not confirmed. The case report shows that the overlap of the clinical phenotypes of diabetes displays the diversity of diabetes in young population. Then, diagnostic process must be carefully planned to exclude other diabetes forms and accurately ascertain childhood diabetes type.