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Condition report · Endocrine

MODY (Maturity-Onset Diabetes of the Young)

Whole genome sequencing identifies all 14+ MODY genes (GCK, HNF1A, HNF4A, HNF1B, and others) plus evaluates type 2 diabetes polygenic risk score, providing the complete genetic diabetes evaluation that distinguishes monogenic from polygenic diabetes.

A condition report looks for rare variants known to cause the conditions it covers.

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About this condition

A monogenic form of diabetes, usually diagnosed in adolescence or early adulthood, characterized by impaired insulin secretion.

Maturity-onset diabetes of the young (MODY) is a group of monogenic diabetes subtypes caused by single-gene variants affecting β-cell function. MODY accounts for approximately 1-2% of all diabetes, but up to 80% of MODY cases are misdiagnosed as type 1 or type 2 diabetes because MODY shares clinical features with both. MODY should be suspected in diabetes with onset before age 35, negative islet autoantibodies, preserved C-peptide, and/or a strong family history of non-insulin-dependent diabetes across three or more generations (autosomal dominant inheritance with high penetrance).

The MODY gene determines treatment. GCK-MODY (MODY2, ~30% of MODY) causes mild, stable fasting hyperglycemia (typically HbA1c 5.6-7.6%) that does NOT progress, does NOT cause microvascular complications, and does NOT require treatment in most circumstances; insulin and oral hypoglycemics are unnecessary and inappropriate. HNF1A-MODY (MODY3, ~40% of MODY) and HNF4A-MODY (MODY1) respond exquisitely to low-dose sulfonylureas; patients can often discontinue insulin entirely when the correct diagnosis is made. HNF1B-MODY (MODY5) causes diabetes plus renal cysts and requires different management.

Type 2 diabetes is polygenic with approximately 40-70% heritability. Genome-wide association studies have identified >400 common variants contributing to T2D risk, including TCF7L2 (the strongest common variant), KCNJ11, PPARG, SLC30A8, and many others. Polygenic risk scores combining hundreds of variants can stratify T2D risk with clinical utility, particularly in young adults where early risk identification enables preventive lifestyle intervention before diabetes onset. WGS captures both monogenic MODY evaluation and polygenic T2D risk assessment in a single test.

GCK-MODY patients often receive DECADES of unnecessary insulin injections before the correct diagnosis is made. GCK-MODY hyperglycemia is stable, non-progressive, and does not cause complications; treatment is not needed. The correct diagnosis eliminates unnecessary therapy.

The condition we analyse

Autosomal dominant

MODY (maturity-onset diabetes of the young) is a rare, familial, clinically and genetically heterogeneous form of diabetes characterized by young age of onset (generally 10-45 years of age) with maintenance of endogenous insulin production, lack of pancreatic beta-cell autoimmunity, absence of obesity and insulin resistance and extra-pancreatic manifestations in some subtypes.

What a diagnosis changes

GCK-MODY: no treatment needed; HNF1A/HNF4A-MODY: low-dose sulfonylureas; HNF1B-MODY: insulin + renal monitoring; T2D polygenic: lifestyle modification, metformin, GLP-1 agonists, SGLT2 inhibitors based on comorbidity profile

Genes analysed

Also known as

Mason type diabetes; maturity-onset diabetes of the young (disease); MODY

Includes 15 related subtypes ↓
  • Fanconi renotubular syndrome 4 with maturity-onset diabetes of the young
  • maturity-onset diabetes of the young type 1
  • maturity-onset diabetes of the young type 10
  • maturity-onset diabetes of the young type 11
  • maturity-onset diabetes of the young type 13
  • maturity-onset diabetes of the young type 14
  • maturity-onset diabetes of the young type 2
  • maturity-onset diabetes of the young type 3
  • maturity-onset diabetes of the young type 4
  • maturity-onset diabetes of the young type 6
  • maturity-onset diabetes of the young type 7
  • maturity-onset diabetes of the young type 8
  • maturity-onset diabetes of the young type 9
  • maturity-onset diabetes of the young, type 12
  • renal cysts and diabetes syndrome
MONDO:0018911OMIM 606391Orphanet 552MedGen 87433

Why whole genome sequencing

80% of MODY is misdiagnosed. Correct diagnosis eliminates unnecessary insulin (GCK-MODY) or switches from insulin to a simple pill (HNF1A-MODY). The annual cost savings per patient can be $10,000+ with improved glycemic control.

Misdiagnosed GCK-MODY patients receive decades of unnecessary insulin: correct diagnosis eliminates all diabetes medications

GCK (glucokinase) functions as the pancreatic glucose sensor. GCK-MODY resets the fasting glucose setpoint ~1-2 mmol/L above normal, producing stable mild hyperglycemia from birth. This hyperglycemia does NOT progress, does NOT cause retinopathy/nephropathy/neuropathy, and does NOT respond to insulin or metformin (because the glucose setpoint is simply reset, not dysregulated). Patients diagnosed with T2D based on elevated fasting glucose who actually have GCK-MODY are taking medications they don't need, with side effects (hypoglycemia from insulin) for a condition that requires no treatment.

HNF1A-MODY patients on insulin can often switch to sulfonylureas with better control: molecular diagnosis transforms management

HNF1A-MODY (the most common MODY subtype) produces progressive β-cell dysfunction that responds to sulfonylureas at approximately 4x the sensitivity of typical T2D. Many HNF1A-MODY patients misdiagnosed as T1D are on insulin with suboptimal control and hypoglycemic episodes. When molecular HNF1A diagnosis is made and they switch to low-dose sulfonylureas, glycemic control often improves while the treatment burden dramatically decreases (daily pills vs. multiple daily injections). The cost savings and quality of life improvement are substantial.

Other endocrine conditions

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