What is the likely cause of a 7-year-old male patient's elevated blood glucose, presenting with polydipsia, polyphagia, polyuria, and unexplained weight loss?

Type 1 Diabetes is the Diagnosis

This 7-year-old patient has Type 1 diabetes because the presentation of polydipsia, polyuria, polyphagia, unexplained weight loss, ketonuria, and marked hyperglycemia (350 mg/dL) in a young child is pathognomonic for autoimmune β-cell destruction requiring immediate insulin therapy. 1, 2

Why Type 1 Diabetes is Correct

Classic Triad Plus Weight Loss

• The presence of polyphagia (normal appetite despite weight loss) alongside polyuria and polydipsia is a key distinguishing feature of Type 1 diabetes according to the American Academy of Pediatrics 1
• The American Diabetes Association confirms that symptoms of marked hyperglycemia include polyuria, polydipsia, weight loss, sometimes with polyphagia, which this patient clearly demonstrates 3
• These classic symptoms typically occur for several days to a few weeks prior to diagnosis in Type 1 diabetes 3

Age and Presentation Pattern

• Type 1 diabetes accounts for 5-10% of all diabetes cases but is the predominant form in children 4
• Incidence peaks in puberty and early adulthood, but onset can occur at any age, making a 7-year-old a typical presentation age 5
• The acute onset over two weeks with rapid metabolic decompensation is characteristic of Type 1 diabetes 3

Laboratory Confirmation

• Random blood glucose of 350 mg/dL with classic symptoms meets diagnostic criteria immediately per the American College of Endocrinology 1
• The presence of ketonuria indicates insulin deficiency and impending diabetic ketoacidosis, which is pathognomonic for Type 1 diabetes 1, 2
• HbA1c of 10.5% confirms prolonged hyperglycemia consistent with progressive β-cell destruction 1

Why the Other Options are Incorrect

Diabetes Insipidus is Wrong

• Diabetes insipidus causes polyuria but does NOT cause hyperglycemia, glycosuria, or ketonuria 6
• The blood glucose of 350 mg/dL immediately excludes diabetes insipidus as the primary diagnosis 2
• The American Diabetes Association notes that ruling out other causes of polyuria is only necessary if presentation is atypical—the presence of polyphagia strongly suggests diabetes mellitus rather than diabetes insipidus 2

Type 2 Diabetes is Wrong (Both Answer Choices)

• Type 2 diabetes accounts for 90-95% of all diabetes cases but primarily in adults, not children 4
• Type 2 diabetes typically presents insidiously and is often asymptomatic at screening, not with acute symptoms over two weeks 3
• Ketonuria at presentation is uncommon in Type 2 diabetes and suggests absolute insulin deficiency characteristic of Type 1 3
• The claim that abdominal symptoms are unlikely in Type 1 diabetes is false—nausea and stomach pain are common prodromal symptoms of diabetic ketoacidosis in Type 1 diabetes 3

Polyphagia Distinguishes Type 1 from Type 2

• While both types can present with the "three Ps" (polyuria, polydipsia, polyphagia), polyphagia with weight loss is more characteristic of Type 1 diabetes due to absolute insulin deficiency and inability to utilize glucose 1
• Type 2 diabetes patients are typically overweight or obese, not experiencing unexplained weight loss 4

Critical Clinical Pitfall

The American College of Endocrinology warns against delaying insulin initiation in children with marked hyperglycemia and classic symptoms, as this can lead to rapid metabolic decompensation and diabetic ketoacidosis 1. This patient requires immediate insulin therapy without waiting for confirmatory autoantibody testing 1, 2.