Maturity onset diabetes of the young (MODY)


An autosomal dominant condition characterized by pancreatic beta cell dysfunction that causes mild diabetes that is diagnosed during adolescence or early childhood.



MODY refers to any of several hereditary forms of diabetes mellitus caused by mutations in an autosomal dominant gene disrupting insulin production. 



MODY is often referred to as monogenic diabetes.



It is distinguished  from the more common types of diabetes-especially type 1 and type 2- which involve more complex combinations of causes involving multiple genes and environmental factors. 



Has a slow progression to insulin use compared with the rapid progression in type one diabetes, but occurs in relatively young patients. 



Accounts for as many as 5% of presumed type 1 and type 2 diabetes cases in a diabetic clinic population. 



Data from Saxony, Germany, MODY was responsible for 2.4% of diabetes incidence in children younger than 15 years.



Several genes form distinct forms of MODY.



Most forms of MODY cause isolated abnormal glucose levels.



At least 13 genes-GCK which encodes for glucokinase, and HNF1a and HNF4A which encode hepatocyte nuclear factors 1A and 4A, respectively account for most cases.



MODY associated with GCK gene is characterized by mild, non-progressive hyperglycemia present since birth.



MODY associated with HNF1A and HMF4A for a characterized by the development of diabetes in the early teen years or young adulthood, that is initially mild and then progresses affecting patients such that they may need insulin before diagnosis.



With GCK-MODY genetic variants, there is a reduction in the function of glucokinase. 



Glucokinase the pancreatic enzyme in beta cells that function as a glucose sensor and controls the rate of entry of glucose into the glycolytic pathway. 



Reduced sensitivity to glucose induced insulin secretion causes asymptomatic mild fasting hypoglycemia, and upward shift in the normal range of fasting blood,  causes an upward shift in postprandial glucose levels, but with tight regulation maintained.



Glucokinase is the enzyme in pancreatic beta cells that function as a glucose sensor and controls the rate of entry of glucose into the glycolytic pathway. 



Reduced sensitivity to glucose induced insulin secretion, causes a mild asymptomatic fasting hyperglycemia with a blood sugar ranging from 100 to 140 mg/dL and causes an upward shift in postprandial levels.



The mild hyperglycemia that results does not confer a predisposition to diabetic complications. 



It is not altered much by treatment, does not necessitate treatment except for pregnancy.



HNF1A-MODY and HNF4A MODY have progressive hyperglycemia that eventually leads to the necessity of treatment.



HNF1A-MODY and HNF4A-MODY results  in Progressive hyperglycemia eventually requires treatment.



Patients with these  genetic variants can often be treated with oral agents.



MODY 2 and MODY 3 are the most common forms.



MODY should not be confused with latent autoimmune diabetes of adults (LADA) — a form of type 1 DM, with slower progression to insulin dependence than child-onset type 1 DM, and which occurs later in life.



It is the final diagnosis in 1%–2% of people initially diagnosed with diabetes. 



The prevalence is 70–110 per million people. 



50% of first-degree relatives will inherit the same mutation..



First-degree relatives have a greater than 95% lifetime risk of developing MODY themselves. 



Patients present with a strong family history of diabetes and the onset of symptoms is in the second to fifth decade.



Clinically presents as 2 general types:



Significant hyperglycemia and the typical signs and symptoms of diabetes: 



Asymptomatic: Diagnosed either by accident, when a high glucose is discovered during testing for other reasons, or screening of relatives of a person discovered to have diabetes. 



Mild hyperglycemia during a routine glucose tolerance test for pregnancy is a typical presentation.



There are two primary advantages of confirming a MODY diagnosis.



Insulin may not be necessary and it may prompt screening of relatives and so help identify other cases in family members.



In many cases MODY is assumed to be more common forms of diabetes: type 1 if the patient is young and not overweight, type 2 if the patient is overweight, or gestational diabetes if the patient is pregnant. 



MODY is inherited in an autosomal dominant fashion.



Most patients have other members of the family with diabetes, and penetrance differs between the types from 40% to 90%.



MODY 1 125850-Due to a loss-of-function mutation in the HNF4α gene. 5%–10% cases.



MODY 2 125851 glucokinase is due to any of several mutations in the GCK gene, and accounts for 30%–70% cases. 



MODY association with mild fasting hyperglycemia throughout life, small rise on glucose loading. 



Patients with MODY do not tend to get diabetes complications and do not require treatment.



Mutations of the HNF1α gene is a homeobox gene-30%–70% of cases. 



Tends to be responsive to sulfonylureas. 



The forms of MODY are autosomal dominant, requiring only one abnormal gene to produce the disease.



The severity of the MODY is moderated by the presence of a second, normal allele which presumably functions normally. 



Homozygous defects of these genes are much rarer and much more severe in their effects.



All forms of MODY are all due to ineffective insulin production or release by pancreatic beta cells. 



Defects are usually mutations of transcription factor genes. 



For each form of MODY, multiple mutations involving different amino acid substitutions have been discovered. 



Diagnosis: Mild to moderate hyperglycemia (typically 130–250 mg/dl discovered before 30 years of age. 



A first-degree relative with a similar degree of diabetes.



Absence of positive antibodies or other autoimmunity.



Persistence of a low insulin requirement.



Absence of obesity



Insulin resistance very rarely happens.



Cystic kidney disease in patient or close relatives.



Non-transient neonatal diabetes, or apparent type 1 diabetes with onset before six months of age.



MODY diagnosis is confirmed by specific gene testing.



In some forms of MODY, standard treatment is appropriate, though exceptions occur:



In MODY2, oral agents are relatively ineffective, however most patients are managed conservatively through diet and exercise.



In MODY1 and MODY3, sulfonylureas are usually very effective, delaying the need for insulin treatment.



Management is similar to all forms of diabetes: blood testing, changes in diet, physical exercise, oral hypoglycemic agents, and insulin injections. 



Usually goals of management can be achieved more easily with MODY than with ordinary types 1 and 2 diabetes. 



Sulfonylureas remain the oral medication of first resort. 



Patients with MODY less often suffer from obesity and insulin resistance than those with type 2 diabetes.



MODY, the term is now used as a synonym for dominantly inherited, monogenic defects of insulin secretion occurring at any age, and no longer includes any forms of type 2 diabetes.








Leave a Reply

Your email address will not be published. Required fields are marked *