• Decreased production
• Increased destruction
• Sequestration
• Pseudothrombocytopenia

• Artifactually low platelet count due to in vitro clumping of platelets
• Usually caused by antibodies that bind platelets only in presence of chelating agent (EDTA)
• Seen in healthy individuals and in a variety of disease states
• Diagnosis:
 Marked fluctuations in platelet count without apparent cause
 Thrombocytopenia disproprotionate to symptoms
 Clumped platelets on blood smear
 "Platelet satellitism" - platelets stuck to WBC
 Abnormal platelet/leukocyte histograms
 Platelet count varies with different anticoagulants

Platelet clumping in EDTA No clumping in heparin

Blood 2012;119:4100

• Marrow failure (pancytopenia)
 aplastic anemia, chemotherapy, toxins
• B-12, folate or (rarely) iron deficiency
• Viral infection
•
Drugs that can selectively reduce platelet production
 Alcohol
 Estrogens
 Thiazides
 Chlorpropamide
 Interferon
• Amegakaryocytic thrombocytopenia
 myelodysplasia (pre-leukemia)
 immune? (related to aplastic anemia)
• Cyclic thrombocytopenia (rare)
• Inherited thrombocytopenia

• Congenital aplastic anemia/Fanconi's anemia
• Congenital amegakaryocytic thrombocytopenia
• Thrombocytopenia with absent radius syndrome (recessive)
• Bernard-Soulier syndrome (recessive, giant platelets, defective function, GPIb defect)
• May-Hegglin anomaly and related disorders (dominant, leukocyte inclusions, giant platelets, MYH-9 mutation)
• Other autosomal dominant syndromes (platelets may be normal or giant)
• Wiskott-Aldrich syndrome (X-linked, immunodeficiency, eczema)

PMN inclusions
Giant platelets
(macrothrombocytopenia)

Macrothrombocyte
Drachman, Blood 2004:103:390
Microthrombocytes

• Benign thrombocytopenia of pregnancy
 Occurs in up to 5% of term pregnancies
 Accounts for about 75% of cases of thrombocytopenia
 Asymptomatic, mild, occurs late in gestation
• Microangiopathy (Preeclampsia/eclampsia, HELLP)
• ITP (? increased incidence in pregnancy)

•
•
•
•

• Autoimmune (ITP)
 Childhood
 Adult
• Drug-induced
 Heparin
 Quinine, others
• Immune complex (infection, etc)
• Alloimmune
 Post-transfusion purpura
 Neonatal purpura

• Caused by re-exposure to foreign platelet antigen via blood product transfusion
– Almost all cases in multiparous women
– HPA-1a (formerly PL A1) antigen most commonly involved (present in 98% of population)
• Antibodies cause destruction of patient’s own platelets by uncertain mechanism
– Possibly due to coating of patient’s platelet by donor platelet microparticles
• Typically presents as sudden onset of severe thrombocytopenia
(<10K) 5-7 days after transfusion
– Consider this diagnosis whenever there is sudden, severe, unexplained drop in platelet count in hospitalized patient
• Diagnosis: clinical suspicion, demonstrate anti HPA-1a (or other) alloantibodies in serum
• Treatment: IVIG, avoid giving HPA-1a positive platelets; wash RBC to remove passenger platelets

• Immune complex-mediated platelet destruction
 Childhood ITP
 Bacterial sepsis
 Hepatitis C, other viral infections
• Activation of coagulation cascade
 Sepsis with DIC
• Vascular/endothelial cell damage
 Viral hemorrhagic fevers
 Rocky Mountain Spotted Fever
• Damage to platelet membrane components by bacterial enzymes (eg, S pneumoniae sialidase)
• Decreased platelet production
 Viral infections (EBV, measles)
• Mixed production defect/immune consumption
 HIV infection

DRUG-INDUCED IMMUNE THROMBOCYTOPENIA
• Quinine type:
 Drug binds to platelet membrane
 Antibody binds to drug
 Exposed Fc portion targets platelet for destruction
 Thrombocytopenia typically severe, with bleeding
 Some patients develop microangiopathy with renal failure
(HUS)
• Heparin type:
 Heparin-platelet factor 4 complex forms on platelet surface
 Antibody binds to complex
 Fc portion of antibody binds to platelet/monocyte Fc receptor
 Platelet and monocyte activation triggered
 Thrombocytopenia typically mild to moderate
 Associated with thrombosis in many patients

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Hematology 2009;153

• Childhood form (most < 10 yrs old)
 May follow viral infection, vaccination
 Peak incidence in fall & winter
 ~50% receive some treatment
 ≥75% in remission within 6 mo
• Adult form
 No prodrome
 Chronic, recurrences common
 Spontaneous remission rate about 5%

Childhood (acute) ITP
Adult (chronic) ITP

Epidemiology (adults)
•
Prevalence: 1-10/100,000
•
Slightly more common in women
•
Peak incidence at age 60+
•
About 40% have an associated disorder

• SLE
• Antiphospholipid syndrome
• CLL
• Large granular lymphocyte syndrome
• Autoimmune hemolytic anemia (Evans syndrome)
• Common variable immune deficiency
• Autoimmune lymphoproliferative disorder (ALPS)
• Autoimmune thyroid disease
• Sarcoidosis
• Carcinomas
• Lymphoma
• H pylori infection
• Following stem cell or organ transplantation
• Following vaccination

A PROSPECTIVE STUDY OF ITP IN 245 ADULTS
• Overall incidence 1.6/100,000/yr
• Median age 56, F:M 1.2:1
• 12% presented with bleeding, 28% asymptomatic
• 18% needed no treatment
• Only 12% needed splenectomy
• 63% in remission (plts > 100K) at end of followup period (6-78 mo, median 60)
• 87% had at least partial remission (plts
>30K) and freedom from symptoms
• 1.6% died from complications of disease or its treatment
Age-specific incidence
Brit J Haematol 2003;122:966

Pathogenesis
• ITP plasma induces thrombocytopenia in normal subjects
• Platelet-reactive autoantibodies present in most cases
 Often specific for a platelet membrane glycoprotein
• Antibody coated platelets cleared by tissue macrophages
 Most destruction in spleen (extravascular)
• Most subjects have compensatory increase in platelet production
• Impaired production in some (many?) patients
 Intramedullary destruction?
 Enhanced TPO clearance?

Splenectomy specimen from a patient with chronic ITP. Left: (40x) Activated lymphoid follicles with expanded marginal zone (short arrow), a well-defined dark mantle zone (long arrow), and a germinal center containing activated lymphocytes
(arrowhead). Right: (1000x) PAS stain showing histiocytes with phagocytized platelet polysachharides (arrows). Transfusion 2005;45:287

Clinical features and diagnosis
• Petechiae, purpura, sometimes mucosal bleeding
• Major internal/intracranial bleeding rare
• Mortality rate < 5%
• Absence of constitutional symptoms or splenomegaly
• Other blood counts and coagulation parameters normal
• No schistocytes or platelet clumps on blood smear
• Marrow shows normal or increased megakaryocytes
(optional)
• Rule out other causes of thrombocytopenia (HIV, etc)

Confirmatory laboratory testing
• Serum antiplatelet antibody assay (poor sensitivity)
• Test for specific anti-platelet glycoprotein antibodies (more specific, negative in 10-30%)
Confirmatory testing not necessary in typical cases

Management
• Platelets > 20-30 K, no bleeding: no Rx
 30-70% recover within 3 weeks
• Platelets < 10K, or < 20K with significant bleeding: IVIg or corticosteroids
 prednisone, 1-2 mg/kg/day
 single dose IVIg 0.8-1g/kg as effective as repeated dosing
• Splenectomy reserved for chronic ITP (> 12 mo) or refractory disease with life-threatening bleeding
 pre-immunize with pneumococcal, H. influenzae and meningococcal vaccines

Treatment of newly diagnosed adults
Indications:
 Platelets < 20-30K
 Active bleeding or high bleeding risk, platelets <50K
First line treatment options:
 Glucocorticoids
 IVIG
 Anti-Rh globulin (WinRho)
 Splenectomy
 Rituximab?
Hospitalization often not necessary

Glucocorticoid therapy
• Mechanism of action: Slows platelet destruction, reduces autoantibody production
• Prednisone, 1-2 mg/kg/day (single daily dose)
• Begin slow taper after 2-4 weeks (if patient responds)
• Consider alternative therapy if no response within 3-4 weeks
• About 2/3 of patients respond (plts > 50K) within 1 week
• Most patients relapse when steroids withdrawn
Advantages: high response rate, outpatient therapy
Disadvantages: steroid toxicity (increases with time and dose), high relapse rate

Splenectomy
• Sustained remission in 2/3 of patients
• Almost all responses occur within 7-10 days of splenectomy
• Operative mortality < 1%
• Severe intra- and postoperative hemorrhage rare (about 1% of patients)
• Laparoscopic splenectomy usually preferable technique
• Advantage: High sustained response/cure rate
• Disadvantages: Operative risk (mainly older pts with comorbid disease); post-splenectomy sepsis (fatality rate 1/1500 patientyrs); increased risk of cardiovascular events
• Indication: Steroid failure or relapse after steroid Rx (persistent severe thrombocytopenia or significant bleeding)

• 66% complete response rate (2632 patients)
• No preoperative characteristic consistently predicted response
Type of procedure
Open
Mortality Complication
1%
Laparoscopic 0.2% rate
12.9%
9.6%
Blood 2004;104:2623

Intravenous immunoglobulin therapy
• Possible mechanisms of action:
 Slowed platelet consumption by Fc receptor blockade
 Accelerated autoantibody catabolism
 Reduced autoantibody production
• Dose: 0.4 g/kg/d x 5 days (alternative: 1 g/kg/d x 2 days)
• About 75% response rate, usually within a few days to a week
• Over 75% of responders return to pre-treatment levels within a month
Advantages: rapid acting, low toxicity
Disadvantages: high cost, short duration of benefit, high relapse rate
Indications: Lifethreatening bleeding; pre-operative correction of platelet count, steroids contraindicated or ineffective

Treatment options for relapsed or refractory disease
• No treatment (platelets > 10-20K, no major bleeding or bleeding risk)
• Corticosteroids (low-dose, or pulse high dose)
• I.V. Ig (frequent Rx, very expensive)
• Accessory splenectomy
• Vinca alkaloids
• Danazol
• Colchicine
• Eradication of H. pylori, if present
 Rituximab
 Thrombopoiesis-stimuating drugs
Romiplostim (Nplate)
Eltrombopag (Promacta)
Accessory spleen

• Background: Most patients treated for ITP with corticosteroids relapse when steroids are withdrawn. Many patients can be cured by splenectomy, but some are not. Treatments for relapsed and chronic ITP and adults have variable efficacy.
• Subjects: 57 adults with chronic ITP, with platelet counts <30K. All had at least 2 prior ITP treatments and 31 had been splenectomized.
• Intervention: Rituximab, 375 mg/m2 weekly x 4 doses
• Outcome: Overall 54% response rate (32% with plts >150K, 22% with plts
50-150K). 89% of complete responders remained in remission a median of
72.5 weeks after treatment. Toxicity was minimal.
• Conclusion: Rituximab is a promising treatment for chronic/refractory ITP
British Journal of Haematology 2004; 125: 232
–239

Outcomes 5 years after response to rituximab therapy in children and adults with immune thrombocytopenia
Vivek L. Patel, Matthieu Mahévas, Soo Y. Lee, Roberto Stasi, Susanna Cunningham-Rundles, Bertrand Godeau, Julie Kanter,
Ellis Neufeld, Tillmann Taube, Ugo Ramenghi, Shalini Shenoy, Mary J. Ward, Nino Mihatov, Vinay L. Patel, Philippe Bierling,
Martin Lesser, Nichola Cooper, and James B. Bussel
• 26% of children and 21% of adults with ITP who had an intial response (CR or PR) to rituximab remained in remission without further treatment after 5 years
• No major toxicity observed
• Children did not relapse after 2 years, but adults did
Blood 2012;119:5989

ROMIPLOSTIM FOR CHRONIC ITP
• Patients: 125 patients with chronic ITP (about half had been splenectomized)
• Intervention: Random assignment to treatment with romiplostim
(AMG 531) or placebo
•
Endpoint: Durable platelet response (platelets at least 50K during at least 6 of last 8 wks of treatment)
• Outcome: 16/42 splenectomized patients had durable response with romiplostim, vs 0/21 with placebo. 25/41 nonsplenectomized pts had durable response with romiplostim vs
1/21 with placebo. 20/23 pts on romiplostim stopped or reduced concurrent treatment for ITP, vs 6/16 on placebo.
• No significant toxicity from romiplostim
Lancet 2008;371:395

Lancet 2008;371:395

Lancet 2010

McMillan and Durette, Blood 2004;104:956-60
11 deaths from ITPrelated bleeding;
6 deaths from complications of
Treatment (5%)
Median time to remission 46 mo

•
•
•
•
•

• Up to 50% of patients with ITP and concomitant H pylori infection improve after eradication of infection
• Confirm infection via breath test, stool antigen test or endoscopy
• Higher response rates in:
• Patients from countries with high background rates of infection
• Patients with less severe thrombocytopenia

• Mild cases indistinguishable from gestational thrombocytopenia
• Rule out eclampsia, HIV etc
•
Indications for treatment
 platelets < 10K
 platelets < 30K in 2nd/3rd trimester, or with bleeding
•
Treatment of choice is IVIg
 corticosteroids may cause gestational diabetes, fetal toxicity
• Splenectomy for severe, refractory disease
 some increased risk of preterm labor; technically difficult in
3rd trimester
•
Potential for neonatal thrombocytopenia (approx 15% incidence)
 consider fetal blood sampling in selected cases
 consider Cesarian delivery if fetal platelets < 20K