Aplastic anemia

Definition Panctopenia with hypocellularity A rare and serious condition, aplastic anemia can develop at any age, though it's most common in younger people. Aplastic anemia is a condition that occurs when the body stops producing enough new blood cells bacause the bone marrow does not produce sufficient new cells to replenish blood cells including red and white blood cells as well as platelets.

Definition The term 'aplastic' means the marrow suffers from an aplasia that renders it unable to function properly. Anemia refers to low red blood cell counts, but aplastic anemia patients have lower counts of all three blood cell types: red blood cells, white blood cells, and platelets, termed pancytopenia Aplastic anemia presents with fatigue and at higher risk of infections and uncontrolled bleeding.

Definition Frequently occurs without a known cause. Acquired aplastic anemia is distinguished from iatrogenic marrow aplasia, marrow hypocellularity after intensive cytotoxic chemotherapy for cancer. Known causes include exposure to chemicals (benzene, toluene in glues, insecticides, solvents), drugs (chemotherapy, gold, seizure medications, antibiotics, and others), viruses (HIV, Epstein-Barr), radiation, immune conditions (systemic lupus erythematosus, rheumatoid arthritis), pregnancy, paroxysmal nocturnal hemoglobinuria, and inherited disorders (Fanconi's anemia).

Etiology 70% of aplastic anemia cases are idiopathic, but other known causes are: Hereditary: o Fanconi anemia o Dyskeratosis congenital o Schwachman-Diamond syndrome o Amegakaryocytic thrombocytopenia

Etiology Acquired: o Direct stem cell destruction o Drugs o Toxic chemicals o Infection (viral, hepatitis) o Immune disorders o Collagen vascular diseases

Etiology Most cases of aplatic anemia are idiopathic, little other than history separates these cases from those presumed etilogy such as a drog exposure. Some of these include: Radiation, chamicals, drugs, infections, immunologic disease, pregnancy, paroxysmal nocturnal hemoglobinuria

Radiation Marrow aplasia is a major acute sequela of radiation. Radiation damages DNA; tissues dependent on active mitosis are particularly susceptible. Radiation dose can be approx from the rate and degree of decline in blood counts, dosimetry by reconstruction of exposure can help to estimate the patient’s prognosis and also to protect medical personnel.

Chemicals Benzene primarily affects the CNS and the hematopoietic system. Aplastic anemia caused by bone marrow suppression is the classic cause of death in chronic benzene poisoning. The clinical and hematologic picture of aplastic anemia resulting from benzene exposure is not different from classical aplastic anemia; in some cases, mild bilirubinemia, changes in osmotic fragility, increase in lactic dehydrogenase and fecal urobilinogen, and occasionally some neurological abnormalities are found

Drugs Drugs which are most strongly suspected of causing aplastic anaemia include several drugs which are chemotherapeutic drugs, arthritis, particularly rheumatoid arthritis (particularly anti-inflammatory drugs which are used in the treatment of rheumatoid arthritis), drugs used to control overactive thyroid, some drugs used in psychiatry and a few antibiotics. For most drugs, monitoring the blood count is not of use in preventing the disease because of the delay between taking the drug and the risk of developing aplastic anemia. Once the blood count begins to fall the disease has been triggered and withdrawal of the drug will not reverse this.

Infections Hepatitis is the most common preceding infection, and posthepatitis marrow failure accounts for about 5% of etiologies in most series. Aplastic anemia can rarely follow infectious mononuncleosis, and EBV has been found in the marrow of a few patients, some w/o a suggestive preceding history

Immunologic Diseases Aplasia is a major consequence and inevitable cause of death in Transfusion- associated graft-versus-host disease. It is strongly associated with the rare collagen vascular syndrome called eosinophilic fascitis Pancytopenia with marrow hypoplasia can also occur in SLE.

Pregnancy Aplastic anemia very rarely may occur and recur during pregnancy and resolve with delivery or with spontaneous or induced abortion.

Paroxysmal Nocturnal Hemoglobinuria Paroxysmal nocturnal hemoglobinuria (PNH), sometimes referred to as Marchiafava-Micheli syndrome, is a rare, acquired, potentially life- threatening disease of the blood characterised by complement-induced hemolytic anemia (anemia due to destruction of red blood cells in the bloodstream), red urine (due to the appearance of hemoglobin in the urine) and thrombosis