Immune thrombocytopenic purpura

Background

• Abbreviation: ITP
• Known as both "idiopathic" or "immune" thrombocytopenic purpura
• Acquired autoimmune disease resulting in destruction of platelets
• Because circulating platelets are functional, life-threatening bleeding only once platelet count <10K

Types

Charateristic	Acute ITP	Chronic ITP
Common age group	Younger children	Adults
Sex	Affects men/women equally	Usually women
Duration	Resolves in 1-2 months	Lasts > 3 months
Cause	Typically follows viral illness	More likely to have an underlying disease or autoimmune disorder (e.g. SLE)
Prognosis		Rarely remits spontaneously or with treatment

Clinical Features

• Petechiae
• Epistaxis
• Gingival bleeding
• Menorrhagia
• GI bleeding
• Intracranial hemorrhage

Differential Diagnosis

Thrombocytopenia

Decreased production

• Marrow infiltration (tumor or infection)
• Viral infections (rubella, HIV)
• Marrow Suppression (commonly chemotherapy or radiation)
• Congentital thrombocytopenia
  • Fanconi anemia
  • Alport syndrome
  • Bernand Soulier
• Vitamin B12 and/or folate deficiency

Increased platelet destruction or use

• Idiopathic thrombocytopenic purpura
• Thrombotic Thrombocytopenic Purpura (TTP)
• Hemolytic Uremic Syndrome (HUS)
• Disseminated Intravascular Coagulation (DIC)
• Viral infections (HIV, mumps, varicella, EBV)
• Drugs (heparin, protamine)
• Postransfusion or Posttransplantation
• Autoimmune destruction (SLE or Sarcoidosis)
• Mechanical destruction
  • Artificial valves
  • ECMO
• HELLP syndrome
• Excessive hemorrhage
• Hemodialysis, extracorporeal circulation
• Splenic Sequestration
  • Occurs in Sickle cell disease and Cirrhosis

Drug Induced

• sulfa antibiotics, ETOH, ASA, thiazides/furosemide

Comparision by Etiology

	ITP	TTP	HUS	HIT	DIC
↓ PLT	Yes	Yes	Yes	Yes	Yes
↑PT/INR	No	No	No	+/-	Yes
MAHA	No	Yes	Yes	No	No
↓ Fibrinogen	No	No	No	No	Yes
Ok to give PLT	Yes	No	No	No	Yes

Petechiae/Purpura (by cause)

• Abnormal platelet count and/or coagulation
  • Septicemia
  • Idiopathic thrombocytopenic purpura (ITP)
  • Hemolytic uremic syndrome
  • Leukemia
  • Coagulopathies (e.g. hemophilia)
  • Henoch-Schonlein Purpura (HSP)
  • Acute hemorrhagic edema of infancy (AHEI)
• Hypersensitivity vasculitis
• Primary vasculitides
  • Wegener's
  • Microscopic polyangiitis
  • Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome)
• Secondary vasculitides
  • Connective tissue disorder
    • Systemic lupus erythematosus
  • Scurvy
  • Infectious disease
    • Hepatitis B
    • Hepatitis C
• Trauma

Evaluation

• Diagnosis of exclusion
• Must differentiate acute ITP from chronic ITP, which suggests an underlying disorder
• CBC shows normal cell lines except for the platelets (may have mild anemia)

Management

Options

• First choice in adults: Corticosteroids
  • Prednisone 60-100mg/d with taper after count reaches normal (50-75% remission rate by 3 wks)
  • Methylprednisolone 30mg/kg/d IV x 3 days (for life-threatening bleeding)
• First choice in children: Intravenous Immunoglobulin G (IVIG) 1gm/kg/d x 2 days
• High dose Anti-D (RhoGAM): patient must be Rh+ for it to work
  • Causes shift towards splenic destruction of antibody-coated Rh+ RBCs
  • Thereby has less functional capacity to destroy platelets
  • Dosage dependent on Hb level in mg/dL
    • Hb>10, 250 IU/kg IV x1 over 5min
    • Hb<10, 125 IU/kg IV x1 over 5min
• Platelet transfusion
  • Indicated for life-threatening bleeding
  • Will ultimately be destroyed
  • Transfuse only following first dose of methylprednisolone or IVIG
    • Holding transfusion until after first dose results in greater rise in platelet count
    • Calculate number of packs needed to increase count to over 50k (1 pack generally increases by 10k)
• Estrogen for uterine bleeding: 25mg IV x1

Indications

Adults

• Platlet >30K and asymptomatic: usually do not require treatment
• Platlet count <30K: prednisone
• Platlet <50K AND bleeding: prednisone
• Life-threatening bleeding: IVIG, methylprednisolone, platelet transfusion

Children

• Platelet count >30K: usually do not require treatment
• Platelet count <20K + significant bleeding: IVIG
• Platelet count <10K: IVIG
• Life-threatening bleeding: IVIG, methylprednisolone, platelet transfusion

Other Options

• Splenectomy if above fails
• Rho(D) Immune Globulin (RhoGAM)
  • Will induce mild hemolysis in Rh+ patients that decreases macrophage activity
  • Spleen will not destroy platelets covered in antibodies
• Rituximab
  • May help as ITP is autoimmune process

Disposition

• Admit: platelet count <20K or significant mucous membrane bleeding
• Discharge: platelet count >20K AND asymptomatic OR only minor petechiae

Complications

• Rare: more common in elderly
  • Intracerebral bleeding
  • Severe GI bleeding

See Also

• ITP in Pregnancy

References

Authors

Ross Donaldson