What are the other Names for this Condition? (Also known as/Synonyms)

• Idiopathic Aplastic Anemia

What is Acquired Aplastic Anemia? (Definition/Background Information)

• Aplastic anemia is a disorder that occurs due to bone marrow failure. Bone marrow is the soft, yellow (fatty) tissue located in the center of the bone
• The blood cells are formed by stem cells located in the bone marrow. The 3 major types of blood cells are RBCs (red blood cells), WBCs (white blood cells), and platelets
• In aplastic anemia, these stem cells are destroyed; due to which, the production of all the 3 blood cell types are affected, leading to a decreased count of blood cells (pancytopenia)

Aplastic anemia is broadly classified into Inherited Aplastic Anemia and Acquired Aplastic Anemia. Acquired Aplastic Anemia is a rare disorder:

• In 75% of the cases, the cause is not identified, in which case it is known as Idiopathic Aplastic Anemia
• In about 25% of the cases of Acquired Aplastic Anemia, the cause may be identified

Who gets Acquired Aplastic Anemia? (Age and Sex Distribution)

• Although Acquired Aplastic Anemia commonly affects teenagers and young adults, it can also affect individuals of any age group
• Both males and females are affected
• The condition may rarely affect pregnant women
• It is two times more common in Asia than in the Western regions (Europe and America)

What are the Risk Factors for Acquired Aplastic Anemia? (Predisposing Factors)

The risk factors of Acquired Aplastic Anemia include:

• In a majority of individuals diagnosed with Acquired Aplastic Anemia, the risk factors are unknown or unidentified
• In a small subset of individuals, there is an identifiable factor. However, not ever individual who is exposed to these factors may be affected by the condition. The factors include:
• Exposure to chemicals such as benzene, insecticides, and pesticides
• Use of medications such as chloramphenicol, phenylbutazone, carbamazepine, felbamate, phenytoin, quinine, phenylbutazone, and many other drugs
• Infections, especially hepatitis, cytomegalovirus (CMV), Epstein-Barr (EBV)
• High-dose chemotherapy administered to individuals diagnosed with cancer

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Acquired Aplastic Anemia? (Etiology)

Acquired Aplastic Anemia is a serious condition that affects blood production. For many individuals with the condition, the causative factor is unknown. However, in some, the causative factors are partially known. These may include:

• Researchers believe autoimmune mechanisms play a major role in the development of Acquired Aplastic Anemia. In autoimmune diseases, one's own immunity targets specific cells and tissues in the body and causes destruction. In Acquired Aplastic Anemia, the immune cells attack and destroy the bone marrow stem cells
• The risk factors (like medications such as benzene, chloramphenicol) are believed to activate one's immunity to act against the hematopoietic bone marrow stem cells

Depending on the blood cell count Acquired Aplastic Anemia can be classified as mild, moderate, and severe; with mild type having the maximum number of cells, and severe having the least number of cells.

What are the Signs and Symptoms of Acquired Aplastic Anemia?

The signs and symptoms of Acquired Aplastic Anemia may slowly develop over a long period of time or they can manifest in an acute manner. On the basis of which specific blood cell type is affected, the signs and symptoms can be:

Due to decrease in the number of red blood cells (anemia):

• Fatigue (increased desire to sleep), weakness
• Dizziness, light-headedness
• Shortness of breath, difficulty breathing
• Pale skin
• Chest pain
• Headache

Due to decrease in the number of white blood cells (leukopenia):

• Frequent infections or,
• Life-threatening infections

Due to decrease in the number of platelets (thrombocytopenia):

• Easy bruising with minimal trauma
• Bleeding of the gums
• Nosebleeds
• Increased menstrual blood flow
• Spontaneous life-threatening internal bleed

How is Acquired Aplastic Anemia Diagnosed?

The diagnostic tools used for Acquired Aplastic Anemia may include:

• Thorough evaluation of the individual’s medical history and a complete physical examination
• An evaluation of medical history will determine if there is a presence of predisposing factors such as:
  • History of cancer and chemotherapy
  • Recent infections
  • Use of certain medications, or exposure to chemicals/toxins           
• Physical examination can reveal signs associated with decrease in blood cell type numbers
• Whenever blood test results indicate a decrease in all 3 cell types, Acquired Aplastic Anemia must be highly suspected. The blood tests include:
  • Complete blood count (CBC), which may show decrease in the number of RBCs, WBCs, and platelets
  • Bleeding time may be increased            

A bone marrow biopsy may be performed to make a definitive diagnosis of Acquired Aplastic Anemia. It may reveal an absence of the precursor cells that form all the 3 blood cell types. It is also done to rule-out other diseases, such as myelodysplastic syndrome (MDS) and paroxysmal nocturnal hemoglobinuria (PNH), which may be associated with Acquired Aplastic Anemia.

• Bone marrow aspiration and biopsy are usually performed on the pelvic bone. But, it can also be performed on the breast bone (sternum), or a leg bone (below the knee, above the foot)
• In this procedure, a large hollow needle is inserted through the skin, muscle, tissue and finally into the bone. The doctor uses twisting hand motion to penetrate the bone and push the needle into the bone marrow cavity. The fluid from the bone marrow is then extracted and the needle withdrawn
• The extracted fluid/tissue is sent to the lab for examination by a pathologist to make a definitive diagnosis. The pathologist may order special tests as required

Other tests for Acquired Aplastic Anemia may be ordered to check for any predisposing factors, as advised by the healthcare provider.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Acquired Aplastic Anemia?

The complications of Acquired Aplastic Anemia include:

• Severe, life-threatening bleeding in the internal organs such as the brain or abdomen
• Severe, life-threatening infections
• Heart failure
• Progression to myelodysplasia, leukemia (blood cancer)

How is Acquired Aplastic Anemia Treated?

The treatment of Acquired Aplastic Anemia varies. It is based on the age and health status (mild or severe condition) of the affected individual, and the availability of bone marrow donors.

The initial treatment is attempted at symptomatic improvement of the individual. They include:

• Packed cell volume (blood transfusion) to increase the count of red blood cells, for relief from anemic symptoms
• Platelet transfusion to counter any active bleeding
• Antibiotics to treat infections
• It is also important to remove any known causative factors such as medications

Long-term treatment options may include:

• Allogeneic bone marrow transplant: This is the most preferred treatment in children and young adults. In this type of bone marrow transplantation, chemotherapy or radiation is used to destroy the abnormal bone marrow cells. These are then replaced by normal bone marrow cells from a donor by injecting them intravenously into the patient's body, where they travel to the bone marrow and begin to produce new blood cells. Ideally, the best match is obtained from identical twins, siblings, or close relatives having the closest genetic makeup of the individual. But, most of the times, the donors are not necessarily related and only a basic compatibility is sought
• Peripheral stem cell transplantation: Another, similar procedure known as peripheral stem cell transplantation is also used to treat Acquired Aplastic Anemia. In this case, the donor's blood stream is the source of the stem cells, which are intravenously injected into the patient's blood. However, generally better results are obtained with a bone marrow transplant instead of a peripheral stem cell transplant
• Immune suppressive therapy to suppress autoimmune trigger mechanisms: This is the treatment of choice for those who cannot undergo a bone marrow transplant, either due to advanced age or unavailability of a suitable donor. The most common immunosuppressants used are anti-thymocyte globulin and cyclosporine. Although, the therapy is effective in bringing the individual's blood count back to normal or near normal range for longer duration, it is only a temporary measure and needs to be repeated if aplastic anemia recurs. Moreover, the individual is still at risk of developing PNH, myelodysplasia, or leukemia, as immunosuppressive therapy has no effect in preventing those conditions
• Hematopoietic growth factors: It is used when individuals do not respond to immunosuppressive therapy. The growth factors such as granulocyte-macrophage colony-stimulating factor (GM-CSF), erythropoietin (EPO), and granulocyte-colony stimulating factor (G-CSF) are injected into the bloodstream, to stimulate the production of blood cells. The procedure may assist in increasing the counts

How can Acquired Aplastic Anemia be Prevented?

Currently there are no known methods to prevent Acquired Aplastic Anemia:

• It is an autoimmune disease with no trigger factors observed in a majority of the individuals
• There are a few known causative factors, but not each individual to the causative factors are affected by Acquired Aplastic Anemia. It is thus difficult to predict who will develop this condition

What is the Prognosis of Acquired Aplastic Anemia? (Outcomes/Resolutions)

• Acquired Aplastic Anemia can sometimes, be present for a brief period of time, or it may become chronic (longer period). The severity of the condition varies from one individual to another
• The prognosis depends on severity of the condition, availability of matched donors, access to tertiary care facilities, complications arising from bone marrow transplant and immunosuppressive therapy
• If left untreated, Acquired Aplastic Anemia may lead to death

Additional and Relevant Useful Information for Acquired Aplastic Anemia:

• In the US, up to 1000 individuals are diagnosed with Acquired Aplastic Anemia every year
• The function of the three major blood cells produced in the bone marrow include:
  • RBCs or erythrocytes: They carry and deliver oxygen from the lungs to the tissues so that they can carry out cellular respiration
  • WBCs or leukocytes: These cells fight against infection and also play a role in inflammation
  • Platelets: These cells help in clot formation whenever there is a bleeding