Forms of Presentation and Progression of Diabetes in Children Under One Year Old

A case series describing four infants under one year of age presenting with different forms of diabetes, including transient neonatal diabetes, IPEX syndrome, type 1 diabetes mellitus, and monogenic diabetes due to KCNJ11 mutation. The report highlights varied clinical presentations, diagnostic challenges, and the critical role of molecular testing in guiding accurate diagnosis, personalized treatment, and long-term management.

A case series describing four infants under one year of age presenting with different forms of diabetes, including transient neonatal diabetes, IPEX syndrome, type 1 diabetes mellitus, and monogenic diabetes due to KCNJ11 mutation. The report highlights varied clinical presentations, diagnostic challenges, and the critical role of molecular testing in guiding accurate diagnosis, personalized treatment, and long-term management.

Updated:

27 March 2026

Introduction

Diabetes in children under one year old can present severe and nonspecific forms, such as type 1 Diabetes Mellitus (DMT1), monogenic forms, neonatal diabetes (permanent or transient) and diabetes-associated syndromes (IPEX).

Aim

Introduce four patients under one year old with different presentations and progression of diabetes forms.

Methods

PATIENT 1: A twelve-day-old female newborn is admitted with vomits, weakness and polyuria; glycemia: 922 mg/dl, HbA1C: 4,9%. Insulin therapy was indicated until she was one month old.

PATIENT 2: An eleven-day male newborn is admitted due to hypovolemic shock and metabolic acidosis with glycemia 580 mg/dl. During the follow-up secretory diarrhea, very high IgE level and primary hypothyroidism were found.

PATIENT 3: An eight-month-old male is admitted due to diabetic debut in severe ketoacidosis (pH 6,9, bicarbonate 3), glycemia 530 mg/dl, Hb1Ac 12% and protein tyrosine phosphatase antibody 14,7 UI/ml (+).

PATIENT 4: A three-month-old male with bronchiolitis, glycemia 300 mg/dl and HbA1c 11%. Insulin therapy was indicated until he was 10 months old.

Patient	Age/ Sex	Presentation	Initial tests	Diagnosis	Treatment	Outcome
1	12-day-old Female	Vomits, weakness, polyuria	Glu: 922 mg/dl HbA1c: 5.7 %	Transient Neonatal Diabetes (6q24 mutation)	Basal-bolus insulin for 3 months	Two hyperglycemia episodes during acute illness. Then excellent evolution (HbA1c 5,7%) C-peptide 1.32 ng/ml
2	11-day-old Male	Hypovolemic shock, metabolic acidosis	Glu: 580 mg/dl	IPEX syndrome (FOXP3 mutation)	Microinfusion insulin, 2 bone marrow transplants	Secretory diarrhea, high IgE level and primary hypothyroidism. Suboptimal control (HbA1c 8,8%)
3	8-month-old Male	Severe ketoacidosis	Glu: 530 mg/dl HbA1c: 12 % AC IA-2 14.2(+)	Type 1 Diabetes Mellitus	Basal-bolus insulin, CGM	Suboptimal control (HbA1c 8,3 %)
4	3-month-old Male	Bronchiolitis	Glu: 300 mg/dl HbA1c: 11 %	KAPT channel defect (KCNJ11 mutation)	Insulin for 7 months. Then glibenclamide	Good control (HbA1c 6%) C-peptide <0.54ng/ml

Results

Mutation in locus 6q24 confirms Transient Neonatal Diabetes. She initiated basal-bolus insuline regimen for only 3 months. She presented two hyperglycemia episodes during acute illness and required corrections with s.c insulin and acquired hypothyroidism was diagnosed. Excellent evolution. Last HbA1C: 5,7%

IPEX syndrome was confirmed by mutation of the gene encoding FOXP3. He is undergoing insulin therapy by microinfusion. He underwent 2 bone marrow transplants. His glycemic control is poor. Last HbA1c 8.8%.

Sequence analysis KCNJ11 and INS genes did not detect a disease-causing variant. DMT1 was assumed and the patient received a basal-bolus insulin regimen. Now, he uses a continuous glucose monitoring sensor, with poor glycemic control. Last HbA1c 8.3%.

Mutation in KCNJ11 gene encoding the Kir6.2

subunit of KATP channel was confirmed, identifying a heterozygous pathogenic variant (p.(Trp68Cys), c.4214T>C). He was transferred to glibenclamide. Glucose monitoring with HB1Ac 6% and C- Peptide <

0.54 ng/ml is performed.

Mutation in locus 6q24 confirms Transient Neonatal Diabetes. She initiated basal-bolus insuline regimen for only 3 months. She presented two hyperglycemia episodes during acute illness and required corrections with s.c insulin and acquired hypothyroidism was diagnosed. Excellent evolution. Last HbA1C: 5,7%.

Conclusion

Patients under one year old can be misdiagnosed regarding different diabetes forms. Molecular biology is key, since it leads to an accurate diagnosis, thus an adequate treatment and follow-up.