Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology is usually 150,000–450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration Splenic sequestration Severe Congenital Neutropenia of platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship are often asymptomatic until platelet counts Platelet counts The number of platelets per unit volume in a sample of venous blood. Coagulation Studies are < 50,000/µL. Clinical manifestations of thrombocytopenia include easy bruising Easy bruising Chédiak-Higashi Syndrome or bleeding, petechiae Petechiae Primary Skin Lesions, purpura, and when severe, spontaneous mucosal and/or internal bleeding. Diagnosis is made with a CBC and blood smear Blood smear Myeloperoxidase Deficiency; additional testing may be required to determine the underlying etiology if it is not evident from the clinical scenario. Management involves treating the underlying etiology and platelet transfusions.
Last updated: 7 May, 2021
Thrombocytopenia is a deficiency of platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology, typically defined as < 150,000 platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology per microliter of whole blood.
Thrombocytopenia can be classified as mild, moderate, or severe on the basis of platelet counts Platelet counts The number of platelets per unit volume in a sample of venous blood. Coagulation Studies:
Thrombocytopenia can be caused by decreased production, increased destruction, or sequestration of platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology.
Mechanism | Examples |
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Decreased production | Failure of
bone
Bone
Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy.
Bones: Structure and Types marrow:
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Decreased
thrombopoietin
Thrombopoietin
A humoral factor that stimulates the production of thrombocytes (blood platelets). Thrombopoietin stimulates the proliferation of bone marrow megakaryocytes and their release of blood platelets. The process is called thrombopoiesis.
Platelets: Histology:
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Nutritional:
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Congenital
Congenital
Chorioretinitis:
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Increased destruction | Immune-mediated:
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Consumption in thrombi |
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Sequestration in the spleen Spleen The spleen is the largest lymphoid organ in the body, located in the LUQ of the abdomen, superior to the left kidney and posterior to the stomach at the level of the 9th-11th ribs just below the diaphragm. The spleen is highly vascular and acts as an important blood filter, cleansing the blood of pathogens and damaged erythrocytes. Spleen: Anatomy |
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Mixed or unclear mechanisms | Infection-induced thrombocytopenia:
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Dilution |
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Pseudothrombocytopenia (a falsely low platelet count due to clumping) |
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Under normal physiologic conditions, platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology are produced from the fragmentation Fragmentation Chronic Apophyseal Injury of megakaryocytes in the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types marrow.
Platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology are the principle cells involved in formation of the initial platelet plug Platelet plug Hemostasis (i.e., primary hemostasis Primary hemostasis Hemostasis).
Formation of the temporary hemostatic plug:
The disrupted endothelial surface exposes VWF to the passing blood.
Platelets
Platelets
Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm.
Platelets: Histology
bind
BIND
Hyperbilirubinemia of the Newborn to the VWF via their GpIb
receptors
Receptors
Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell.
Receptors and are activated.
Platelet activation
Platelet activation
A series of progressive, overlapping events, triggered by exposure of the platelets to subendothelial tissue. These events include shape change, adhesiveness, aggregation, and release reactions. When carried through to completion, these events lead to the formation of a stable hemostatic plug.
Hemostasis
triggers
Triggers
Hereditary Angioedema (C1 Esterase Inhibitor Deficiency) them to secrete ADP, which stimulates the expression of the GpIIb/IIIa
receptors
Receptors
Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell.
Receptors on the
platelets
Platelets
Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm.
Platelets: Histology. The GpIIb/IIIa
receptors
Receptors
Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell.
Receptors
bind
BIND
Hyperbilirubinemia of the Newborn to
fibrinogen
Fibrinogen
Plasma glycoprotein clotted by thrombin, composed of a dimer of three non-identical pairs of polypeptide chains (alpha, beta, gamma) held together by disulfide bonds. Fibrinogen clotting is a sol-gel change involving complex molecular arrangements: whereas fibrinogen is cleaved by thrombin to form polypeptides a and b, the proteolytic action of other enzymes yields different fibrinogen degradation products.
Hemostasis, which is able to
bind
BIND
Hyperbilirubinemia of the Newborn a platelet on each end, causing
platelets
Platelets
Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm.
Platelets: Histology to aggregate. As more
platelets
Platelets
Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm.
Platelets: Histology are bound to one another, the
platelet plug
Platelet plug
Hemostasis is generated. As the
coagulation cascade
Coagulation cascade
The coagulation cascade is a series of reactions that ultimately generates a strong, cross-linked fibrin clot.
Hemostasis is activated,
thrombin
Thrombin
An enzyme formed from prothrombin that converts fibrinogen to fibrin.
Hemostasis converts the weaker
fibrinogen
Fibrinogen
Plasma glycoprotein clotted by thrombin, composed of a dimer of three non-identical pairs of polypeptide chains (alpha, beta, gamma) held together by disulfide bonds. Fibrinogen clotting is a sol-gel change involving complex molecular arrangements: whereas fibrinogen is cleaved by thrombin to form polypeptides a and b, the proteolytic action of other enzymes yields different fibrinogen degradation products.
Hemostasis into the stronger
fibrin
Fibrin
A protein derived from fibrinogen in the presence of thrombin, which forms part of the blood clot.
Rapidly Progressive Glomerulonephritis, creating a much more stable clot.
In thrombocytopenia, a platelet deficiency results in:
Drug-induced thrombocytopenia may be due to direct toxic effects on the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types marrow (e.g., chemotherapy Chemotherapy Osteosarcoma) or to drug-dependent antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions. Drug-dependent antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions:
Unlike most drug-induced thrombocytopenias, HIT is associated with a markedly increased risk of thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus rather than bleeding.
Petechiae Petechiae Primary Skin Lesions on the lower leg Leg The lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg: Anatomy of a patient with immune thrombocytopenic purpura Immune thrombocytopenic purpura Immune thrombocytopenic purpura (ITP), formerly known as idiopathic thrombocytopenic purpura, is a condition that develops secondary to immune-mediated destruction of platelets, resulting in thrombocytopenia (platelet count < 100,000/mm³). Immune thrombocytopenic purpura can be either primary or secondary due to drugs or underlying disease. Immune Thrombocytopenic Purpura
Image: “ Petechiae Petechiae Primary Skin Lesions on lower leg Leg The lower leg, or just “leg” in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg: Anatomy” by James Heilman, MD. License: CC BY-SA 4.0Purpura evident on the distal extremities of a pediatric patient
Image: “Purpura2” by Okwikikim. License: Public DomainThe diagnosis of thrombocytopenia itself is made with laboratory evaluations. Clues to the underlying etiology can be obtained from the history and exam, and additional lab testing can further aid in diagnosis.
The following tests should be ordered for all patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with thrombocytopenia:
Peripheral blood film in a patient with
DIC
DIC
Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage.
Disseminated Intravascular Coagulation demonstrating thrombocytopenia,
schistocytes
Schistocytes
Hemolytic Uremic Syndrome, and spherocytes:
Many reticulocytes (immature
RBCs
RBCs
Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production.
Erythrocytes: Histology) are present, indicating a brisk hematopoietic
bone
Bone
Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy.
Bones: Structure and Types marrow response.
Platelet counts
Platelet counts
The number of platelets per unit volume in a sample of venous blood.
Coagulation Studies are reduced (none seen here) because of consumption due to
DIC
DIC
Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage.
Disseminated Intravascular Coagulation. Normally, there should be at least 8
platelets
Platelets
Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm.
Platelets: Histology in a single 1000×-oil-immersion field; 1 platelet indicates approximately 20,000
platelets
Platelets
Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm.
Platelets: Histology/µL in the peripheral blood.
Peripheral smears showing a paucity of platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology
Image: “ Peripheral blood smear Peripheral Blood Smear Anemia: Overview and Types and bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types marrow aspirate” by Shabneez Hussain. License: CC BY 2.0The following tests should be ordered only as clinically indicated to help identify the underlying etiology.
Hypocellular bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types marrow in a patient with aplastic anemia Aplastic Anemia Aplastic anemia (AA) is a rare, life-threatening condition characterized by pancytopenia and hypocellularity of the bone marrow (in the absence of any abnormal cells) reflecting damage to hematopoietic stem cells. Aplastic anemia can be acquired or inherited, however, most cases of AA are acquired and caused by autoimmune damage to hematopoietic stem cells. Aplastic Anemia
Image: “Hypocellular bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types marrow showing only little hematopoiesis Hematopoiesis The development and formation of various types of blood cells. Hematopoiesis can take place in the bone marrow (medullary) or outside the bone marrow (extramedullary hematopoiesis). Bone Marrow: Composition and Hematopoiesis” by Department of Obstetrics of Gynaecology, Erasmus University Medical Center, PO Box 2040, 3000 CA CA Condylomata acuminata are a clinical manifestation of genital HPV infection. Condylomata acuminata are described as raised, pearly, flesh-colored, papular, cauliflower-like lesions seen in the anogenital region that may cause itching, pain, or bleeding. Condylomata Acuminata (Genital Warts) Rotterdam, The Netherlands. License: CC BY 2.0Management of thrombocytopenia depends mainly on addressing the underlying cause, monitoring platelet counts Platelet counts The number of platelets per unit volume in a sample of venous blood. Coagulation Studies, and preventing/controlling any bleeding complications.