Pure Red Cell Aplasia (PRCA)
There are three types of PRCA:
Acquired Pure Red Cell Aplasia: This is a very rare condition and usually affects adults. It is characterized by an absence of red cell precursors (reticulocytes) in the marrow and a low red blood cell count. The amounts of white blood cells and platelet remain normal.
Transient or Acute Self-limited PRCA: This is the most common type of PRCA. It is identical to acquired PRCA except that, at some point, it simply goes away. Transient PRCA is usually triggered by a virus or drug. In most cases, when the virus clears, or the responsible drugs are eliminated, the PRCA will disappear. This is most dangerous to patients who already have a chronic hemolytic anemia. Patients with otherwise normal functioning bone marrow may even recover without having known they had it.
Inherited or Congenital Pure Red Cell Aplasia (Diamond-Blackfan Anemia): Diamond-Blackfan anemia is a genetic condition usually diagnosed during the first two years of life. About half of patients also have physical malformations or mental retardation. Only several hundred cases have been reported worldwide. The severity of the disease varies by patient.
Relation to bone marrow failure diseases:
The major difference between PRCA and aplastic anemia is that, in PRCA, only the red blood cell line is affected, while the white blood cells and platelets remain at normal levels. In aplastic anemia, all three blood cell types are typically affected.
The cause of most cases of PRCA is most recently thought to be autoimmune in nature. Doctors think it is caused by a mistaken attack by the patient’s own immune cells on blood-forming stem cells. There are other more rare causes as well. The risk factors for PRCA include:
- Having autoimmune disorders, such as rheumatoid arthritis, hepatitis or having a large population of clonal large granular lymphocytes which attack the red cell precursors in the marrow
- Tumors of the thymus or thymomas
- Viruses such as the parvovirus B19
- Certain inherited genetic disorders, appearing mostly in early childhood
By definition, all PRCA patients have anemia. Symptoms of anemia can include:
- Pale skin
- Shortness of breath
Acquired PRCA can be caused by an underlying condition that may add other symptoms.
Tests and tools doctors use to diagnose PRCA include:
- Physical exam and history
- Blood tests:
- A complete blood count with a differential that looks at the total number and type of blood cells in your blood
- A reticulocyte count to determine blood levels of young red cells
- A blood smear so your doctor can look at your blood under a microscope
- Bone marrow examination, including aspiration and biopsy to see how your bone marrow looks (required for diagnosis)
The treatment goal is to restore red blood cell production and to treat any underlying disorder. The most common treatments are:
- Blood Transfusions to increase red blood cell levels. Patients who don’t respond to other treatments may need to rely on transfusions on an ongoing basis.
- Corticosteroids, like prednisone, are often the initial treatment for PRCA. Unfortunately, the large doses that are often required can have severe side effects. For that reason, corticosteroid medications are rarely used alone as a treatment.
- Immunosuppressive therapy may be used if the underlying cause of the PRCA is immunological and the patient hasn’t responded to corticosteroids. Drug therapies include cyclophosphamide, cyclosporine, azathioprine with or without corticosteroids, and anti-thymocyte globulin. In some cases, rituximab may be effective. PRCA caused by viruses (especially B19 parvovirus) is treated with immunoglobulin infusions. Thymoma-associated PCRA has to be treated with surgical removal of the thymoma. There is a significant relapse rate after immunosuppressive therapy, but treatments can be repeated.