Flashcards in Platelet Disorders Deck (84)
What is the normal lifespan of a platelet?
Name nine conditions associated with thrombocytopenia.
ITP, DIC, thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), HELLP syndrome (Hemolytic anemia, Elevated Liver function tests, Low Platelets), dilution, transfusion, amniotic fluid embolism, and drug-induced thrombocytopenia.
Name (6) drugs that can cause thrombocytopenia.
Heparin, quinine, quinidine, phenytoin, gold salts, and alcohol.
What is the expected platelet morphology in patients with Bernard-Soulier syndrome?
What is the expected platelet morphology in patients with Wiskott-Aldrich syndrome?
What are the expected smear findings in patients with MYH9-related disorders?
Large platelets and white cell inclusions called Dohle bodies
What is the expected platelet morphology in patients with gray platelet syndrome?
What is Wiskott-Aldrich syndrome?
An extremely rare X-linked disorder characterized by severe thrombocytopenia and small platelets that can develop in the neonatal period. Affected males develop eczema and immunodeficiency.
How might one differentiate between the thrombocytopenia of Wiskott-Aldrich syndrome and that of ITP?
Platelets are small in Wiskott-Aldrich, and large in ITP.
What oncologic process are patients with Wiskott-Aldrich at higher risk for developing?
What are the expected clinical features of patients with Wiskott-Aldrich syndrome?
Severe thrombocytopenia with small platelets, eczema, and immunodeficiency.
What is the inheritance pattern associated with Wiskott-Aldrich syndrome?
What are the clinical characteristics of patients with MYH9-related disorders?
Bleeding tendency, renal failure, sensorineural hearing loss, and/or cataracts.
What is TAR syndrome?
Amegakaryocytic Thrombocytopenia with Absent Radii. An inherited disorder that presents with bleeding in the neonatal period. Thrombocytopenia is severe, and there is an increased risk of death during the neonatal period and early infancy as a result of intracranial bleeds associated with platelet counts of <30,000.
When do most patients with TAR syndrome present?
Half are symptomatic within the first week of life, and 90% are symptomatic by 4 months of age.
How might one differentiate between patients with absent radii due to TAR syndrome vs those with absent radii due to Fanconi anemia or Trisomy 18?
Patients with TAR syndrome have absent radii but normal thumbs. Those with Fanconi anemia and Trisomy 18 have absent radii and abnormal thumbs.
What physical exam abnormalities can be seen in patients with TAR syndrome?
Absent radii, other upper extremity abnormalities (hypoplastic carpals and phalanges, syndactyly, clinodactyly, and phocomelia), lower extremity abnormalities (hip dysplasia, femoral and/or tibial torsion, and deformities of the knees and/or feet), dysmorphic facial features (micrognathia, hypertelorism, broad forehead, low-set and posteriorly rotated ears), and congenital heart disease (most often ASD, VSD, or tetralogy of Fallot).
How is clinically significant bleeding treated in patients with TAR syndrome?
With platelet transfusion.
What are the three potential processes for the development of acquired thrombocytopenia?
Decreased production of platelets, increased destruction of platelets, and sequestration of platelets in an enlarged spleen.
What should you suspect if a patient with sepsis has associated thrombocytopenia?
What blood disorder is common in neonates with CMV?
What is pseudothrombocytopenia?
It is not true thrombocytopenia. Platelets clump together in the collection tube, resulting in a factitiously low platelet count on the automated reader.
What is the next diagnostic step if a patient has an unexpectedly very low platelet count after previously having normal counts?
Review the smear to look for pseudothrombocytopenia. If present, redraw the sample in a sodium citrate tube to prevent clumping and thus provide an accurate count.
What preceding medical history is commonly reported in children diagnosed with ITP?
A history of recent (in the preceding 1-6 weeks) viral infection or immunization is found in a large percentage of those affected.
What is usually the first clinical sign of ITP?
Acute bruising, petechiae, or bleeding.
Within what age range does the peak incidence of ITP occur in children?
Between 2 and 5 years of age.
In what population is chronic ITP more common?
Chronic ITP more commonly occurs in adolescents and adults.
What is the incidence of intracranial hemorrhage in patients with ITP?
Intracranial hemorrhage occurs in <1% of children with ITP and is fatal in 1/3 of these cases.
Describe the peripheral blood smear findings in ITP.
The few platelets seen on the smear are megathrombocytes - large, but not as large as RBCs.