Definition

Aplastic anemia is a disorder in which the bone marrow
greatly decreases or stops production of blood cells.

Description

The bone marrow (soft tissue which is located within
the hard outer shell of the bones) is responsible for the
production of all the types of blood cells. The mature
forms of these cells include red blood cells, which carry
oxygen throughout the body; white blood cells, which
fight infection; and platelets, which are involved in clotting.
In aplastic anemia, the basic structure of the marrow
becomes abnormal, and those cells responsible for generating
blood cells (hematopoietic cells) are greatly
decreased in number or absent. These hematopoietic
cells are replaced by large quantities of fat.

Yearly, aplastic anemia strikes about 5-10 people in
every one million. Although aplastic anemia strikes both
males and females of all ages, there are two age groups
that have an increased risk. Both young adults (between
15-30 years of age) and the elderly (over the age of 60)
have higher rates of aplastic anemia than the general
population. While the disorder occurs worldwide, young
adults in Asia have a higher disease rate than do populations
in North America and Europe.

Causes and symptoms

Aplastic anemia falls into three basic categories,
based on the origin of its cause: idiopathic, acquired, and
hereditary.

In about 60% of cases, aplastic anemia is considered
to be idiopathic, meaning that the cause of the disorder is
unknown.

Acquired aplastic anemia refers to those cases where
certain environmental factors and physical conditions
seem to be associated with development of the disease.

Acquired aplastic anemia can be associated with: