Non Typical Type 1 Diabetes Mellitus Onset in a Child With Salt-Wasting Congenital Adrenal Hyperplasia.

Type 1 diabetes mellitus (T1DM) and congenital adrenal hyperplasia (CAH) are 2 complex endocrine disorders with neighboring genetic loci. We present a case of T1DM onset in a 6-year-old child, already affected by 21-hydroxylase deficiency (salt-wasting CAH) diagnosed at 18 days of age, who was referred to our clinic because of typical symptoms of diabetes despite nondiagnostic fasting blood glucose values. Further analysis revealed elevated glycated hemoglobin (HbA1c), low C-peptide, and specific autoantibodies suggesting the diagnosis of T1DM. Although he only started with rapid-acting insulin analogue before meals, he presented spontaneous episodes of hypoglycemia just before the morning hydrocortisone dose, due to an underdosed glucocorticoid intake. Based on continuous glycemic monitoring (CGM), his morning dose was increased and given earlier; then we decided to apply an advanced hybrid closed-loop insulin pump to maintain glycemic time in range above 70%. Fasting glucose in CAH patients can be lower due to underdosed glucocorticoid replacement therapy. HbA1c and CGM can help recognize T1DM onset and evaluate the correct dosage of corticosteroid therapy in CAH patients. New studies are needed to understand the therapeutic approach for a more specific treatment in case of coexistence of these diseases.