Type 1 diabetes mellitus (T1D) is a growing public health concern in Saudi Arabia, ranking ninth globally in T1D incidence and tenth in T1D prevalence in children, and the rates are expected to rise and incur greater healthcare costs. Genetic and immunological factors are believed to play a significant role in disease development, and recent clinical trials have shown promise in delaying or preventing T1D onset in high-risk individuals. Early screening for immunological or genetic markers in children is crucial to identify high-risk individuals and provide early intervention. Last year, the American diabetes association's recommended clinicians to screen first degree relatives of individual with T1D. Unfortunately, Saudi Arabia and other Arab countries lack established T1D screening programs, making early identification and intervention challenging. The benefits of screening include education for symptom awareness, monitoring to track progression to clinical T1D, a five-fold reduction in diabetic ketoacidosis (DKA) at onset, and improved glucose control for the first years following diagnosis. To address this issue, exploring effective and efficient screening methods in identifying high-risk children and the cultural acceptability, feasibility, and barriers to a broader implementation of such screening programs among Saudi families is crucial. Therefore, the investigators aim to conduct a prospective cohort study among young children and adolescents with a family history of T1D (i.e., T1D first-degree relatives). Children 2-18 years old will be screened using a 5 spots filter-dried blood sample for the following:

1. Islet autoantibodies: IAA, GADA, IA-2A, Zn-transporter autoantibodies using the antibody detection by agglutination PCR (ADAP) assay.
2. HLA phenotyping
3. Genetic risk score after the cross-sectional assessment those who are determined to be in stage I, or II of T1D will be offered prospective follow-up for 5 years.

Inclusion Criteria:

• T1D diagnosis in a first-degree relative:

Diabetes is defined based on the American diabetes association (ADA) definition: Classic symptoms of diabetes or hyperglycemic crisis, with plasma glucose concentration ≥11.1 mmol/L (200 mg/dL), or Fasting plasma glucose ≥7.0 mmol/L (≥126 mg/dL). Fasting is defined as no caloric intake for at least 8 h, or Two-hour post load glucose ≥11.1 mmol/L (≥200 mg/dL) during an OGTT, or HbA1c >6.5%.

Exclusion Criteria:

• first-degree relative case with Maturity-Onset Diabetes of the Young (MODY) or Type 2 Diabetes Mellitus (T2DM).
• Non-Saudi children.
• first-degree relative not following at our centre.

2-18 years old health children with first-degree relatives with T1D.

The data is available from the PI upon reasonable request and approval by the IRB.