Thrombocytopenia

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Contents 1 More Specific Terms 2 Introduction 3 Etiology 4 Genetics 5 Clinical-manifestations 6 Laboratory 7 Radiology 8 Differential-diagnosis 9 Management 10 More General Terms 11 Additional Terms 12 Internet Database 13 References

More Specific Terms

• Evan's syndrome
• heparin-induced thrombocytopenia (HIT)
• HIV-induced thrombocytopenia
• immune or idiopathic thrombocytopenic purpura (ITP)
• macrothrombocytopenia
• neonatal alloimmune thrombocytopenia
• post transfusion purpura
• thrombocytopenia of pregnancy (gestational thrombocytopenia)
• thrombotic thrombocytopenic purpura
• X-linked dyserythropoietic anemia & thrombocytopenia
• X-linked thrombocytopenia with beta-thalassemia; thrombocytopenia, platelet dysfunction, hemolysis, & imbalanced globin synthesis

Introduction

• Abnormal decrease in number of the blood platelets. Thrombocytopenia may be classified as:
• mild: 100,000-150,000/ uL
• moderate: 50,000-100,000/ uL
• severe: <50,000/ uL

Etiology

• congenital

• in-utero forms

• autoimmune thrombocytopenia
• infections

• viremia
• bacteremia
• other infections

• drugs
• thrombocytopenia with absent radius syndrome
• vascular malformations

• hereditary forms

• isolated familial thrombocytopenia
• Wiskott-Aldrich syndrome
• Fanconi syndrome
• Alport's syndrome
• Bernard-Soulier disease
• Glanzmann thrombasthenia
• von Willebrand's disease, platelet type
• May-Hegglin anomaly
• Chediak-Higashi syndrome

• diminished platelet production

• metabolite deficiency

• vitamin B12 deficiency
• folate deficiency

• pharmacologic agents (common)

• acetazolamide
• aspirin
• carbamazepine
• carbenicillin
• chlorpropamide
• chlorthalidone
• estrogens
• furosemide
• gold salts
• heparin*
• indomethacin
• isoniazid
• methyldopa
• moxalactam
• phenylbutazone
• phenytoin & other hydantoins
• quinidine
• quinine
• thiazides
• ticarcillin
• others, many

• physical/toxic agents

• radiation
• chemotherapy
• alcohol (common)

• myelophthisis

• granuloma
• tumor
• fibrosis

• infection

• CMV
• HIV
• protozoan
• rickettsial
• other infections

• diminished/defective megakaryocytes

• myelodysplastic syndrome
• myeloproliferative disease
• aplastic anemia
• paroxysmal nocturnal hemoglobinuria
• collagen-vascular disease
• graft vs host disease

• increased platelet destruction

• immune-mediated

• immune thrombocytopenic purpura ( ITP)
• drug-induced
• alloimmune
• bacterial sepsis without DIC
• some infections
• non-specific systemic allergic events

• microangiopathic

• disseminated intravascular coagulation ( DIC)*
• eclampsia
• malignant hypertension
• thrombotic thrombocytopenic purpura ( TTP)*
• hemolytic uremic syndrome
• renal graft allorejection
• intravascular foreign bodies
• vascular malformations
• burns

• hypersplenism
• post-transfusion purpura
• massive transfusion
• hypothermia
• artificial heart valves
• snake venoms

• splenic pooling
• pseudothrombocytopenia
• * Marks thrombocytopenias considered medical emergencies.

Genetics

• defects in MASTL are the cause of thrombocytopenia type 2

Clinical-manifestations

• symptoms:

• mild: 100,000-150,000/ uL - usually asymptomatic
• moderate: 50,000-100,000/ uL

• easy bruisability
• excessive bleeding during trauma

• severe: <50,000/ uL

• excessive bleeding during surgery < 30,000
• <10,000-20,000 - risk of spontaneous bleeding

• spontaneous bleeding, especially mucosal bleeding due to thrombocytopenia tend to occur immediately after trauma
• non-specific symptoms

• do not distinguish thrombocytopenia as a cause from coagulation disorders
• hematoma
• ecchymosis
• purpura
• organ bleeding

• headache in the setting of severe thrombocytopenia may be a symptom of intracranial bleeding

• signs:

• petechia are much more often a sign of platelet disorders than a sign of microvascular disease
• hemorrhagic petechiae or bullae on mucous membranes may indicate a high risk of clinically significant bleeding

Laboratory

• peripheral blood smear
• partial thromboplastin time ( PTT)
• prothrombin time (PT)
• complete blood count ( CBC)
• fibrin split products
• bone marrow biopsy

Radiology

• CT for evaluation of splenomegaly ( hypersplenism)

Differential-diagnosis

• thrombocytopenia & schistocytes on peripheral smear

• disseminated intravascular coagulaion ( DIC)
• thrombotic thrombocytopenic purpura ( TTP); hemolytic uremic syndrome ( HUS)

• thrombocytopenia & platelet clumps on peripheral smear

• pseudothrombocytopenia

• thrombocytopenia, disorder in 2 cell lines, tear drop cells -> myelodysplasia
• thrombocytopenia, anemia, leukopenia & lymphocytosis

• aplastic anemia

Management

• thrombocytopenias requiring emergency treatment

• heparin-induced thrombocytopenia
• disseminated intravascular coagulation ( DIC)
• thrombotic thrombocytopenic purpura ( TTP)

• platelet transfusions

• each unit or transfused platelets should increase the platelet count by 5000-10,000/ uL in the absence of active platelet destruction
• premedication to avoid febrile & allergic reactions

• hydrocortisone
• diphenhydramine ( Benadryl)
• acetaminophen ( Tylenol)

• contraindications to platelet transfusions:

• thrombotic thrombocytopenic purpura ( TTP)
• hemolytic uremic syndrome ( HUS)
• post-transfusion purpura

• specific treatment for specific causes of thrombocytopenia
• activity

• < 10,000/ mm3: no exercise or active physical therapy
• 10,000-20,000/ mm3

• no resistance training
• aerobic exercise ok

• > 30,000: exercise not restricted

More General Terms

• platelet disorder
• sign/symptom

Additional Terms

• disseminated intravascular coagulation (DIC)
• hemolytic uremic syndrome (HUS)
• hereditary disorders associated with thrombocytopenia
• paroxysmal nocturnal hemoglobinuria (PNH, Marchiafava-Micheli syndrome)
• pseudothrombocytopenia

Internet Database

OMIM: 188000

References

1. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 590-94
2. Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 829-39
3. Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
4. National Guideline Clearinghouse Thrombocytopenia (Finnish Medical Society Duodecim) ngc-guideline: [1]

thrombocytopenia