Bone marrow failure

Bone marrow failure is the absence of hematopoietic precursors, stem cells that can develop into all types of blood cells. These stem cells are replaced by fat cells (adipocytes) and lead to pancytopenia (deficiency of red blood cells, white blood cells, and platelets in the blood).

The red bone marrow does not produce enough mature red blood cells (RBCs), white blood cells (WBCs), and platelets or the blood cells produced are damaged.

In most cases, the underlying cause cannot be identified.

When there is no identifiable cause, bone marrow failure is called idiopathic. It happens in more than 50% of cases.

The most common known causes of bone marrow failure are:

• Ionizing radiation
• Drugs, such as Chloramphenicol, Phenylbutazone, or gold salts.
• Other causes: Bone marrow failure has also been observed in viral infections: hepatitis B and C, Epstein-Barr virus, Cytomegalovirus, HIV, and Parvovirus B19.

1. Quantitative: Important decrease or complete absence of blood cells
   • Global (affects all three types of blood cells: red blood cells, white blood cells, and platelets)
     • Aplastic anemia
       • Acquired
         • Idiopathic (unknown cause)
         • Secondary
           • Ionizing radiation
           • Drugs (chloramphenicol, antiepileptic drugs, sulfonamides, etc.)
           • Benzene and other industrial toxins
           • Virus
           • Autoimmune diseases (thymoma, hypogammaglobulinemia, eosinophilic fasciitis)
           • Paroxysmal nocturnal hemoglobinuria
           • Pregnancy
           • Anorexia nervosa
       • Congenital or inherited causes
         • Fanconi anemia
         • Dyskeratosis congenita
         • Shwachman-Diamond syndrome
   • Partial (affects only one of the three types of cells)
     • Erythroblastopenia (the bone marrow does not produce enough red blood cells)
     • Agranulocytosis (decrease in white blood cells such as neutrophils, basophils, and eosinophils)
     • Amegakaryocytic thrombocytopenia (decreased number of platelets)
2. Qualitative (dysplastic anemia): normal amount of blood cells with abnormal structure
   • Global
     • Myelodysplastic syndromes
   • Partial
     • Dyserythropoiesis (defective development of red blood cells)
     • Dysgranulopoiesis (defective development of granulocytes)
     • Dysthrombopoiesis (defective development of platelets)

Bone marrow failure is a rare disease with an incidence of 1.5 to 2 cases per million inhabitants per year.

The main symptoms are a consequence of pancytopenia (decrease of red, white blood cells, and platelets in the blood).

• Anemia related symptoms (low level of hemoglobin in the blood) such as weakness, fatigue, headache, or general malaise.
• Thrombocytopenia related symptoms (low level of platelets in the blood) such as mucocutaneous bleeding (ecchymosis or bruising near the surface of the skin, bleeding gums, epistaxis or nose bleeding). Retinal hemorrhage with consequent visual impairment can also appear.
• Symptoms due to granulocytopenia (low levels of granulocytes in the blood) such as oral mucosal ulcers or bacterial infections are less common.

It is commonly suspected when a blood test is performed and there is simultaneously a low level of red blood cells, white blood cells, and platelets in the blood.

Subsequently, a bone marrow aspiration and biopsy should be performed for a better diagnosis.

There are two clinical types of bone marrow failure: a severe one, often mortal before 3 months, and a moderate one with better survival rates.

High levels of reticulocytopenia, granulocytopenia, monocytopenia, and thrombocytopenia have a poorer prognosis.

On the other hand, an increase in Mean Corpuscular Volume (MCV) and HbF (fetal hemoglobin) are identified as a favorable outcome.

In the biopsy, an empty bone marrow and interstitial injury are bad prognostic factors.

The recommended treatment is based on:

1. General care.
   
   First, the underlying cause should be treated if it is known.
   
   Supportive therapy is also important, such as blood transfusions of red blood cells and platelets. Most patients die from bleeding and infection. However, it is important to limit the number of transfusions and doing them only when they are necessary. Patients with hemoglobin level around of 7-8 g/dl can continue their normal life without transfusions.
   
   Platelet transfusion is indicated when there is bleeding diathesis (a tendency to bleed or bruise easily due to lack of coagulation factors) and severe thrombocytopenia (less than 15-20 x 10⁹ platelets/L). Infections must be aggressively treated with a combination of antibiotics, even before the underlying agent is identified.
   
   
2. Specific therapeutics.
   
   Based on various types of measurements:
   1. Immunosuppressive therapy
      
      One of the standard treatments for patients with moderate bone marrow failure is the combination of cyclosporine and horse ATG (antithymocyte globulin) or thymoglobulin.
      
      
   2. Administration of anabolic drugs
      
      It is adequate in moderate cases. Oxymetholone or similar are often used in doses of 2 mg/kg/day, orally. Three to six months are necessary to notice an improvement.
      
      When it is effective, hemoglobin levels are the first to rise, then the white blood cell (WBCs) count, and finally platelet count although platelet count sometimes remains unchanged.
      
      Side effects include virilization, muscle cramps, cholestasis, and hepatic adenoma (rare).
      
      
   3. Bone marrow transplant (BMT)
      
      If a BMT is considered, transfusions must be avoided, especially those from matching donors, since they may increase the probability of rejection.