A platelet is a small colorless cell fragment that has no nucleus of its own. It is produced in the bone marrow and plays a key role in blood coagulation. The normal platelet count level in the blood is about 150-450×109 / L of blood.
Platelet disorders may either display an increase or decrease in platelet count. Diseases that exhibit decreased platelet count can be divided into quantitative and qualitative. Both predisposes an individual to increased bleeding.
Qualitative disorders involve abnormal platelet structure or function due to missing or defective proteins on the platelet membrane’s surface or abnormality in platelet granules. On the other hand, quantitative platelet disorders means circulating platelets are not enough because production is not sufficient or platelets are abnormally being destroyed.
I. Decreased Platelet Production
Reduced production of platelets may be inborn or acquired.
A. Congenital (Inherited) Thrombocytopenia
Inborn reduced platelet production:
- Wiskott-Aldrich syndrome
- Congenital amegakaryocytic thrombocytopenia
- Autoimmune lymphoproliferative syndrome
- Fanconi anemia
It is a hereditary disorder of the immune system (immunodeficiency), which is characterized by the triad of recurrent pyogenic bacterial infections, eczema (atopiclike dermatitis) and skin hemorrhagic coagulation disorders (caused by thrombocytopenia and platelet dysfunction). It is due to a mutation in a gene on the X chromosome (X-linked recessive disease mode of inheritance).
The treatment includes bone marrow transplant, symptomatic therapy, prophylaxis of infections, immunoglobulins, corticosteroids (eczema), transfusion of blood and blood derivatives (bleeding) and gene therapy. A hematopoietic stem cell transplant is the only current hope of cure.
It is one of the most common rare genetic diseases that usually involves the bone marrow where an impaired labor (inability to produce blood cells) is evident.
Moreover, this form of anemia is often associated with birth defects, tendency of bleeding, frequent appearance of liver tumors, short stature, myelodysplastic syndrome (the blood stem cells – immature cells – do not become mature blood cells) in about 60-75% of patients.
Also, in this form of anemia, there are possible notable anomalies like ectopic kidney, pelvic kidney, hydronephrosis and hydroureter, open ductus arteriosus, aortic stenosis, coarctation of aorta, missing lobes of the lungs, atrial septal defect, tetralogy of Fallot, pseudotruncus, and other problems in the development such as Bell’s palsy, arterial malformations of brain tissue.
With over 99% of cases, the disorder is inherited in an autosomal recessive way, which means there are two copies of the abnormal gene having the disease develop.
Statistical data indicate that the condition, Fanconi anemia, occurs approximately in every 300,000 people, which makes the condition quite rare. Some data show that the carriers are rather common in the general population and it is almost present in every 200 person. The male to female ratio is 2:1, making it more common on the side of men.
The disease is diagnosed usually before 7 years of age. About 9% are diagnosed in adults. The median age of onset for megaloblastic anemia (first detected abnormality) is seven years.
Symptoms of Fanconi anemia includes:
- A short stature and skin pigmentation during childhood
- The first signs of blood disorder are petechiae (small red spots on the skin caused by minor bleeding from broken capillary blood vessels) and easy bruising
- A later onset is pallor, susceptibility to infections, fatigue and body malaise
- Abnormalities of the hands and forearms
- In every third patient, there are disorders of the reproductive organs and the gonads (such as hypospadias, undescended testicles, atrophic testes, azoospermia, phimosis, micropenis, in males while, bicornuate “heart-shaped” uterus, atrophy of the vagina, in females)
- Disorders of the vision occur in about 20%
- Developmental disorders of the kidneys and urinary tract occurs in about 20%
- Approximately 22% displays microcephaly (reduced volume and size of the skull), some hydrocephalus; micrognathia (snoffiness)
- There may also be spina bifida (split spine), Klippel–Feil syndrome (congenital fusion of 2 cervical vertebrae), supernumerary (extra) ribs, and Sacrococcygeal sinuses
- Congenital dislocation of the hip (Perthes’ disease)
- Hearing disorder occurs about 10%
- In every tenth patient appears to have slow development (intellectual and development delay)
The long-term treatment of choice is bone marrow transplant. Treatment with hematopoietic (blood cell) growth factors and androgens are temporarily used for bone marrow failure. There will also be blood transfusions to maintain counts and treat symptomatic problems.
B. Acquired Thrombocytopenia
Acquired reduction in the production of platelets are induced with alcohol and medications.
Four (4) general causes:
- Nutritional deficiency: B12, Folate
- Drugs & alcohol
- Viral: HIV, Hep
- Infiltrative disease
II. Increased Platelet Destruction
The increased consumption of platelets can be classified into immunological or non-immunological thrombocytopenia.
A. Immunologic Thrombocytopenia
Immunologic low platelet count:
- Immune thrombocytopenia
- Immune thrombocytopenic purpura (ITP)
- Acquired aplastic anemia
- Neonatal alloimmune thrombocytopenia
- Thrombocytopenia after blood transfusion
- Thrombocytopenia induced by toxins
- Cyclic thrombocytopenia
Immune-mediated thrombocytopenic purpura
The immune-mediated thrombocytopenic purpura, also known as ITP is a condition marked by the development of antibodies against platelets. The creation of these antibodies leads to immune-mediated thrombocytopenia.
Described are two forms of ITP: acute and chronic.
The acute form is more common in children, and usually occurs after recovery from an infection. Frequently, the patient has a non-specific viral infection, although sometimes acute ITP occurs when recovering from a bacterial infection.
While adults may also develop acute ITP, the disease occurs more often to be gradual (chronic ITP). Most adults do not remember the previous viral or bacterial infection. Approximately 90% of patients is younger than 40 years. Interestingly, the chronic form of ITP affects women more than men.
B. Non-immunological Thrombocytopenia
Non-immunological low platelet count:
- Disseminated intravascular coagulation
- Thrombotic thrombocytopenic purpura (TTP)
- Hemolytic-uremic syndrome (HUS)
(HUS) is a disorder manifesting thrombocytopenia, microcytic hemolytic anemia (occurs secondary to decomposition of red blood cells), and renal failure. Most cases of HUS usually follows after an acute illness of infection and pain (stomach cramps) due to diarrhea (bloody). It can appear with nausea, vomiting, and fever.
Typically, a week after, the acute disease develops a clinical picture of HUS. Patients may display yellowing of the skin, paleness, anemia, extreme tiredness, or bleeding in the gastrointestinal tract (mucosa).
The amount of urine may also become reduced, and may appear reddish or brown. Sometimes it is accompanied with laboratory signs indicating kidney failure, where blood pressure may either be normal or elevated. In about 25% of patients, neurological symptoms (like headache and confusion) may occur.
Qualitative platelet disorders
Qualitative platelet disorders are characterized by the disturbances in function. In this case, platelet levels may be normal but are defective and cannot normally perform their function. Examples are:
- Bernard-Soulier syndrome
- Glanzmann Thrombasthenia
Bernard – Soulier syndrome
It is a disease in which there is a dysfunction of blood platelets (thrombocytes). There is a decreased number of platelets (thrombocytopenia) but increased percentage (megathrombocytes) with a high tendency of bleeding.
Detailed studies have shown that in this kind of disease, there is a deficit of one glycoprotein on the surface of platelets needed to bind to von Willebrand factor for a major function in the normal process of coagulation (clotting).
The disease is inherited (autosomal recessive), which means that it takes two copies of the gene in order for the disease to manifest.
Increase in the amount of platelets
Essential thrombocytosis or primary thrombocythemia is a chronic disease myeloproliferative neoplasm in which there is an elevation in the total number of blood platelets (thrombocytes) in the blood.
The exact cause of essential thrombocythemia is not fully known, but it is assumed that there is a certain degree of genetic predisposition.
Some research show that essential thrombocythemia is diagnosed in about 6 persons per 100 000 people in one year. Males are equally affected as females, however with the younger population, a higher percentage goes to females.
The disease is more common among members of the older population, although one in five patients is younger than 40 years.
Symptoms displayed in essential thrombocytosis
Nearly every third patient at the time of diagnosis are without any symptoms and signs. When symptoms and/or signs are present, it commonly includes thrombosis of blood vessels in most patients.
The most frequently occurring symptoms are:
- Headache (the most common neurological symptom), although problems with speech, dizziness, fainting, loss of vision, seizures may also be present.
Pain and gangrene may occur on fingers
- Thrombosis of large blood vessels can affect the blood vessels of extremities (deep vein thrombosis)
- May also affect blood vessels of the heart (coronary syndrome)
- The gastrointestinal tract is very often found with forms of bleeding complications
- Bleeding can also occur in the skin, gums, joints and brain tissue
- Possible occurrence of loss of appetite and body weight
Diagnosis of essential thrombocytosis
Medical history with analysis of the clinical picture and a detailed overview can help clear doubts in this kind of condition, but certainly must be performed with subsequent supplementary tests.
The definitive diagnosis can be achieved with laboratory measurements of platelet levels in the blood. Also, in addition to elevated platelet count, anemia and increase in leukocytes may occur.
During the diagnostic process for the condition in question, a bone marrow sample may be needed.
How to treat essential thrombocytosis:
The treatment of essential thrombocytosis usually involves the administration of hydroxyurea, interferon alfa, radioactive phosphorus 32 and low-dose aspirin on a daily basis.
In emergency cases, plasmapheresis may be an option.
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