Sunday, February 1, 2009

Type 1 diabetes mellitus

Introduction

Diabetes mellitus is a multisystem. Consequences are in the form of biochemical and anatomical. Disturbances in the metabolism of carbohydrates, protein and fat are the biochemical consequences whereas macrovascular and microvascular complications are the anatomical derangements. Absence or deficiency of insulin is the cause which result all the consequences of the type 1 DM. This is a disease of young individuals, not always.

How does it happen (Pathophysiology)?

Type 1 DM is a catabolic disorder in which circulating insulin is very low or absent. This is due to the failure of pancreatic beta cells to respond to all insulin-secretory stimuli. Therefore patients require exogenous insulin to reverse this catabolic condition, prevent ketosis, and normalize lipid and protein metabolism.

This is an autoimmune disease. There are histological evidence of immunological involvement such as lymphocytic infiltration and destruction of insulin-secreting cells of the islets of Langerhans, causing insulin deficiency. Approximately 85% of patients have circulating islet cell antibodies, and the majority also has detectable anti-insulin antibodies before receiving insulin therapy. Most islet cell antibodies are directed against glutamic acid decarboxylase (GAD) within pancreatic B cells.

There is another school of thought and it says that pancreatic beta cell destruction is due to an infectious or environmental agent. It triggers the immune system in a genetically susceptible individual to develop an autoimmune response against altered pancreatic beta cell antigens or molecules in beta cells that resemble a viral protein. Environmental agents that have been hypothesized to induce an attack on beta cell function include viruses (eg, mumps, rubella, Coxsackie B4), toxic chemicals, and exposure to cow's milk in infancy, and cytotoxins.

Recent evidence suggests a role for vitamin D in the pathogenesis and prevention of diabetes mellitus as well.

Epidemiology

This is the commonest metabolic disorder of childhood. Scandinavia has the highest prevalence rates for type 1 DM (ie, approximately 20% of the total number of people with DM), while China and Japan have the lowest prevalence rates, with less than 1% of all people with diabetes. Some of these differences may relate to definitional issues and the completeness of reporting.

Type 1 DM is more common in men than in women.

Type 1 DM usually starts in children aged 4 years or older, with the peak incidence of onset at 11-13 years of age, coinciding with early adolescence and puberty.

Type 1 DM is more common among non-Hispanic whites, followed by African Americans and Hispanic Americans. It is comparatively uncommon among Asians

Type 1 DM is associated with a high morbidity and premature mortality due to complications.

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