Less Common Types Of Diabetes:
Diabetes Caused by Genetic Defects of the Beta Cell
Genetic defects of the beta cell cause several forms of
diabetes. For example, monogenic forms of diabetes result from mutations, or
changes, in a single gene. In most cases of monogenic diabetes, the gene
mutation is inherited. In the remaining cases, the gene mutation develops spontaneously.
Most mutations in monogenic diabetes reduce the body’s ability to produce
insulin. Genetic testing can diagnose most forms of monogenic diabetes.
NDM and MODY are the two main forms of monogenic diabetes. NDM
is a form of diabetes that occurs in the first 6 months of life. Infants with
NDM do not produce enough insulin, leading to an increase in blood glucose. NDM
can be mistaken for the much more common type 1 diabetes, but type 1 diabetes
usually occurs after the first 6 months of life.
MODY usually first occurs during adolescence or early adulthood.
However, MODY sometimes remains undiagnosed until later in life. A number of
different gene mutations have been shown to cause MODY, all of which limit the
pancreas’ ability to produce insulin. This process leads to the high blood
glucose levels characteristic of diabetes.
A number of types of diabetes result from genetic defects in
insulin action. Changes to the insulin receptor may cause mild
hyperglycemia—high blood glucose—or severe diabetes. Symptoms may include
acanthosis nigricans, a skin condition characterized by darkened skin patches,
and, in women, enlarged and cystic ovaries plus virilization and the
development of masculine characteristics such as excess facial hair. Two
syndromes in children, leprechaunism and the Rabson-Mendenhall syndrome, cause
extreme insulin resistance.
Diabetes Caused by Diseases of the Pancreas
Injuries to the pancreas from trauma or disease can cause
diabetes. This category includes pancreatitis, infection, and cancer of the
pancreas. Cystic fibrosis and hemochromatosis can also damage the pancreas
enough to cause diabetes.
Diabetes Caused by Endocrinopathies
Excess amounts of certain hormones that work against the action
of insulin can cause diabetes. These hormones and their related conditions
include growth hormone in acromegaly, cortisol in Cushing’s syndrome, glucagon
in glucagonoma, and epinephrine in pheochromocytoma.
Diabetes Caused by Medications or Chemicals
A number of medications and chemicals can interfere with insulin
secretion, leading to diabetes in people with insulin resistance. These
medications and chemicals include pentamidine, nicotinic acid, glucocorticoids,
thyroid hormone, phenytoin (Dilantin), and Vacor, a rat poison.
Diabetes Caused by Infections
Several infections are associated with the occurrence of
diabetes, including congenital rubella, coxsackievirus B, cytomegalovirus,
adenovirus, and mumps.
Rare Immune-mediated Types of Diabetes
Some immune-mediated disorders are associated with diabetes.
About one-third of people with stiff-man syndrome develop diabetes. In other
autoimmune diseases, such as systemic lupus erythematosus, patients may have
anti-insulin receptor antibodies that cause diabetes by interfering with the
binding of insulin to body tissues.
Other Genetic Syndromes Sometimes Associated with Diabetes
Many genetic syndromes are associated with diabetes. These
conditions include Down syndrome, Klinefelter’s syndrome, Huntington’s chorea,
porphyria, Prader-Willi syndrome, and diabetes insipidus.