{
 "topic": "Thrombocytopenia",
 "slug": "thrombocytopenia",
 "category_id": 15500,
 "summary": "Pediatric thrombocytopenia: the classic ITP presentation and diagnosis-of-exclusion approach, red flags prompting broader work-up, and the distinct differential for neonatal thrombocytopenia.",
 "written_by": "claude-sonnet",
 "references": [
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 ],
 "short": [
  {
   "title": "In short",
   "content": "- Thrombocytopenia is defined as a platelet count under 150,000/mm3 (normal range 150-400 x 10^9/mm3 in children over 1 week old); causes fall into three mechanisms: decreased production, increased destruction, or splenic sequestration.\n- Immune thrombocytopenia (ITP) is the most common cause of acute thrombocytopenia in an otherwise well child, with incidence estimated at 1-6 per 100,000 (one source: 4 per 100,000) children per year; it is a diagnosis of exclusion.\n- Classic ITP presentation: an otherwise healthy child aged 2-10 years (peak 1-4 years, or 2-5 years by another source) with sudden bruising, petechiae, or bleeding 1-4 weeks (up to 1-6 weeks) after a viral illness or immunization; isolated thrombocytopenia (platelets under 100,000/uL, often much lower) with large/reticulated platelets on smear, and no hepatosplenomegaly.\n- 50-65% of ITP patients have a recent viral illness history; 60-75% of children have acute ITP that resolves within 2-4 months regardless of therapy; 5-10% may recur beyond 3 months after apparent resolution, and a minority progress to chronic ITP (over 6 months duration).\n- Intracranial hemorrhage occurs in under 1% of children with ITP but is fatal in about a third of those cases; menstruating girls with platelets under 10,000/uL can have severe blood loss.\n- No additional testing beyond CBC/peripheral smear is needed if the presentation is classic for ITP; if thrombocytopenia persists beyond 3-6 months, further workup includes testing for HIV, hepatitis C, H. pylori, ANA, and anticardiolipin antibodies.\n- Other causes to consider: pseudothrombocytopenia (EDTA-induced platelet clumping - repeat in a citrate or heparin tube), drug-induced thrombocytopenia (sulfonamides, vancomycin, valproic acid, phenytoin, carbamazepine, heparin - onset 1-2 weeks after starting a new drug or acutely after a single dose, recovery within 1-2 days of stopping), SLE (thrombocytopenia is the presenting feature in 20-40% of cases), hemolytic uremic syndrome, DIC, acute leukemia, Wiskott-Aldrich syndrome, type 2B von Willebrand disease, and congenital causes (TAR syndrome, Fanconi anemia).\n- Neonatal thrombocytopenia has distinct causes: maternal (preeclampsia, lupus, ITP, occult TORCH infection), neonatal alloimmune thrombocytopenia (HPA alloimmunity, the most common isolated neonatal cause), hereditary/congenital syndromes (Wiskott-Aldrich, TAR, Fanconi, Turner, Kasabach-Merritt, trisomies), acute illness (sepsis, birth asphyxia, NEC, RDS, PPHN), TORCH/HIV infection, and thrombosis; persistent thrombocytopenia beyond 10 days warrants hematology consultation.\n- Treatment addresses the underlying cause; for ITP, options include observation, IVIG, and corticosteroids, with platelet transfusion reserved to bridge a bleeding crisis; serial platelet counts guide therapy in children without significant clinical bleeding.\n"
  }
 ],
 "long": [
  {
   "title": "Definition",
   "content": "Thrombocytopenia is defined as a platelet count less than 150,000/mm3 (normal range 150-400 x 10^9/mm3 in children older than 1 week). It can arise from decreased platelet production, increased platelet destruction, or splenic sequestration.\n"
  },
  {
   "title": "Epidemiology",
   "content": "Immune thrombocytopenia (ITP), also called immune or idiopathic thrombocytopenic purpura, is the most common cause of acute-onset thrombocytopenia in an otherwise well child, and the most common bleeding disorder presenting in children between 1 and 7 years of age. Reported incidence ranges from 1-6 per 100,000 children per year (one source cites about 4 per 100,000, another estimates 1 in 20,000 children develop autoantibody-mediated thrombocytopenia after a viral exposure). Acute ITP affects boys and girls equally, with peak incidence between 1 and 5 years of age (commonly cited as 2-5 years); chronic ITP more often affects adolescents or adults. ITP appears to occur more often in late winter and spring, following the peak season of viral respiratory illness.\n"
  },
  {
   "title": "Etiology",
   "content": "A recent viral illness or immunization (in the preceding 1-6 weeks) is reported in 50-65% of children with ITP, believed to trigger development of autoantibodies (often directed against the platelet glycoprotein IIb/IIIa complex) that coat circulating platelets, which are then trapped in the spleen and removed by macrophages. Beyond ITP, thrombocytopenia in the pediatric age range is often immune-mediated (including neonatal auto- or alloimmune thrombocytopenia), but can also result from consumptive coagulopathy (DIC, Kasabach-Merritt phenomenon), acute leukemia, and rarer disorders such as Wiskott-Aldrich syndrome and type 2B von Willebrand disease, or occur artifactually with automated cytometers failing to enumerate giant platelet forms (as in Bernard-Soulier syndrome). Other recognized causes include pseudothrombocytopenia (a falsely low count from EDTA-induced platelet clumping, corrected by resampling in a citrate or heparinized tube), drug-induced thrombocytopenia (associated with sulfonamides, vancomycin, valproic acid, phenytoin, carbamazepine, and heparin, typically appearing 1-2 weeks after starting a new medication or acutely after a single dose, with recovery beginning within 1-2 days of stopping the drug), systemic lupus erythematosus (thrombocytopenia can be the initial manifestation, occurring in 20-40% of patients, sometimes with antiphospholipid antibody syndrome), hemolytic uremic syndrome, malignancy, hypersplenism, storage disorders, and congenital causes such as thrombocytopenia-absent radius (TAR) syndrome and Fanconi anemia.\n"
  },
  {
   "title": "Pathophysiology",
   "content": "In ITP, antiplatelet IgG autoantibodies (often against glycoprotein IIb/IIIa) coat circulating platelets; these opsonized platelets are trapped and destroyed in the spleen by macrophages, and the resulting thrombocytopenia may be accompanied by a compensatory increase in bone marrow megakaryocytes.\n"
  },
  {
   "title": "Clinical Features",
   "content": "Classic ITP occurs in an otherwise healthy 2- to 10-year-old child with sudden bruising or bleeding, typically 1-4 weeks after a mild viral illness or vaccination, with generalized petechiae and purpura, isolated thrombocytopenia (platelets under 100,000/uL, and often much lower), normal white blood cell count and hemoglobin, normal PT/PTT, and large or reticulated platelets on peripheral smear. No hepatosplenomegaly is present. Bruising, petechiae, and mucosal bleeding (epistaxis, gum bleeding) are common; major hemorrhage such as severe GI bleeding, hematuria, or intracranial hemorrhage is much less common. Intracranial hemorrhage occurs in under 1% of children with ITP but is fatal in about a third of those cases. In menstruating adolescent girls, a platelet count under 10,000/uL can result in severe blood loss. About 60-75% of children have acute ITP that resolves within 2-4 months of diagnosis regardless of therapy; about 5-10% recur more than 3 months after initial resolution, and thrombocytopenia persisting beyond 6 months is termed chronic ITP.\n"
  },
  {
   "title": "Diagnostics",
   "content": "ITP is a diagnosis of exclusion. No additional testing beyond CBC and peripheral smear is needed if the clinical presentation is fully consistent with ITP. If thrombocytopenia persists longer than 3-6 months, further work-up should include testing for HIV, hepatitis C, and H. pylori infection, along with antinuclear antibody and anticardiolipin antibody testing. A general diagnostic approach to thrombocytopenia starts with history and physical exam, a complete blood count/peripheral smear (and HIV testing) to rule out spurious thrombocytopenia, malaria, or AIDS, then branches based on whether pancytopenia, anemia, or red cell fragments are present (prompting bone marrow examination, direct Coombs test, or ANA testing to evaluate for autoimmune disease, hemolysis, or marrow failure) versus isolated thrombocytopenia (prompting evaluation for congenital anomalies, lymphadenopathy, or a normal exam pointing toward ITP, drug-induced thrombocytopenia, or a congenital thrombocytopenia syndrome).\n"
  },
  {
   "title": "Differential Diagnosis",
   "content": "Key alternative diagnoses to consider include pseudothrombocytopenia, drug-induced thrombocytopenia, SLE, hemolytic uremic syndrome, DIC, acute leukemia, infectious mononucleosis, hypersplenism, and congenital syndromes (TAR syndrome, Fanconi anemia, Wiskott-Aldrich syndrome). Neonatal thrombocytopenia has its own distinct differential: maternal causes (preeclampsia, medications, lupus, ITP, occult TORCH infection), neonatal alloimmune thrombocytopenia (the most common cause in an otherwise healthy newborn), hereditary/congenital syndromes (Wiskott-Aldrich, TAR, Fanconi anemia, Turner syndrome, Kasabach-Merritt syndrome, trisomies), acute neonatal illness (bacterial or fungal sepsis, birth asphyxia, necrotizing enterocolitis, RDS, persistent pulmonary hypertension), TORCH/HIV infection, and thrombosis (associated with indwelling central catheters, or infant of a diabetic mother, dehydration, or asphyxia). Neonatal thrombocytopenia is rarely a primary disorder of megakaryopoiesis; it usually reflects systemic illness or transplacental transfer of maternal antiplatelet antibodies, and is often seen with congenital viral infections (rubella, CMV, toxoplasmosis, syphilis) and perinatal gram-negative bacterial infection. Marked thrombocytopenia with abnormal abdominal findings is a common combination in necrotizing enterocolitis and other causes of necrotic bowel.\n"
  },
  {
   "title": "Treatment",
   "content": "Treatment targets the underlying cause. For ITP, options include observation, intravenous immunoglobulin (IVIG), and corticosteroids; in children without significant clinical bleeding, serial platelet counts help guide the course of therapy. Platelet transfusion is often used to bridge a bleeding crisis regardless of underlying cause, though it does not address the underlying destructive process in immune-mediated thrombocytopenia. In neonates, persistent thrombocytopenia beyond 10 days warrants hematology consultation. Thrombocytopenia in an acutely ill child (including neonates) requires prompt evaluation for underlying viral and bacterial pathogens.\n"
  }
 ],
 "clinical": [
  {
   "title": "Diagnosing Classic ITP versus a More Concerning Cause",
   "content": "In an otherwise healthy 2- to 10-year-old with sudden bruising, petechiae, or mucosal bleeding 1-4 weeks after a mild viral illness or vaccination, confirm isolated thrombocytopenia with a normal white count and hemoglobin, normal PT/PTT, large platelets on smear, and no hepatosplenomegaly - if this pattern holds, no further testing is needed and ITP can be diagnosed clinically. Reassure families that 60-75% of children resolve within 2-4 months regardless of treatment, but counsel on the small (under 1%) but serious risk of intracranial hemorrhage, and specifically warn menstruating adolescents that a platelet count under 10,000/uL raises risk of severe menstrual blood loss. If thrombocytopenia persists beyond 3-6 months, escalate work-up with HIV, hepatitis C, and H. pylori testing plus ANA and anticardiolipin antibodies, since chronic thrombocytopenia raises concern for an underlying disorder like SLE (which presents with thrombocytopenia in 20-40% of cases) rather than simple ITP. Reconsider the diagnosis - and look for pancytopenia, anemia, red cell fragments, hepatosplenomegaly, lymphadenopathy, or congenital anomalies - whenever the presentation deviates from the classic ITP picture, since these findings point toward leukemia, hemolytic uremic syndrome, autoimmune disease, or a congenital marrow-failure syndrome instead.\n"
  },
  {
   "title": "Working Up Neonatal Thrombocytopenia",
   "content": "In a newborn with thrombocytopenia, review the maternal history (preeclampsia, lupus, ITP, medications, occult TORCH infection) and the neonatal clinical status (well-appearing vs. acutely ill) to narrow the cause. In an otherwise healthy newborn, consider neonatal alloimmune thrombocytopenia (HPA alloimmunity) as the most likely isolated cause; in an acutely ill neonate, evaluate for sepsis, birth asphyxia, necrotizing enterocolitis, or TORCH/HIV infection, and consider thrombosis (particularly with an indwelling central catheter) as another cause. Note associated congenital anomalies that might point to Wiskott-Aldrich syndrome, TAR syndrome, Fanconi anemia, Turner syndrome, Kasabach-Merritt syndrome, or a trisomy. Refer to hematology for any neonate with thrombocytopenia persisting beyond 10 days, and pursue prompt evaluation for viral and bacterial pathogens in any acutely ill child (neonate or older) presenting with new thrombocytopenia.\n"
  }
 ]
}