Lecture 21: ITP Flashcards
What is ITP?
Immune Thrombocytopenia (ITP)
is an acquired autoimmune disorder in which the body’s immune system destroys healthy platelets, leaving the patient at risk for spontaneous bleeding and bruising.
What are the three main categories of causes for ITP (Immune Thrombocytopenia)?
- Environmental Exposures
- Loss of Immune Self-tolerance
- Genetic Predisposition
Which environmental factors are known to trigger ITP?
Infections (often viral)
Vaccines
Toxins
Stress
How does loss of immune self-tolerance contribute to ITP?
- Antigen mimicry leads to cross-reactivity
- Anti-platelet IgG antibodies mistakenly target platelets
- Dysfunction of Tregs impairs immune regulation
What genetic factors can predispose someone to developing ITP?
- Family history of autoimmunity
- Known gene mutations
- Can be an early sign of immunodeficiency
What are the main mechanisms that lead to low platelets in ITP?
(1) Increased Platelet Destruction
(2) Decreased Platelet Production
→ Both processes contribute to low platelet counts.
What are the key epidemiologic features of ITP in children?
(1) Incidence: Affects approximately 5 in 100,000 children per year.
(2) Age Group: Most common between ages 2–5 years.
(3) Clinical Course:
- Typically self-resolves within 3–12 months.
- 80% of cases are newly diagnosed (acute), while
20% may become persistent or chronic.
- Note: It is currently not possible to predict which cases will become chronic.
What is the prevalence of ITP in adults?
Prevalence: Approximately 9.5 cases per 100,000 adults at any given time.
What are the common signs and symptoms of ITP?
Purpura (bruising)
Petechiae
Nosebleeds
Heavy menstrual bleeding
Bleeding in mouth or gums
Blood in vomit, urine, or stool
Fatigue
Rarely, intracranial bleeding
Important: Patient could also be asymptomatic!
What lab findings support a diagnosis of ITP?
-Platelet count < 100 x 10⁹/L
- Normal WBC count
- Normal hemoglobin (unless severe bleeding causes anemia)
- Normal cell morphology on blood smear
Is ITP a diagnosis of exclusion? What red flags suggest alternate diagnoses?
- Yes, ITP is a diagnosis of exclusion
(1) Red flags for other diagnoses:
Constitutional symptoms (fever, weight loss, night sweats)
Bone pain
Recurrent thrombocytopenia
Poor response to treatment
(2) Physical red flags:
Lymphadenopathy
Hepatomegaly
Splenomegaly
General appearance of being unwell
Signs of chronic disease
(3) Investigations:
Low Hb
High MCV
Abnormal WBC or neutrophil count
Abnormal smear (cell morphology)
What are the main categories of thrombocytopenia differentials in children?
- Primary ITP
- Primary Immune Deficiency (PID) or Immune
- Dysregulation Disorder
Inherited Platelet Disorders (IPD)
How can ITP relate to inborn errors of immunity (IEI)?
- ITP can be the first sign of an inborn error of immunity (IEI)
- IEI conditions involve:
(1) Infections
(2) Autoimmunity
(3) Allergy
(4) Autoinflammation
(5) Malignancy (cancer) - IEI are complex genetic disorders, and only some causative genes have been identified so far.
What are the main categories of disorders in the immune system spectrum?
(1) Immunodeficiency Disorders:
Recurrent infections
Severe infections
Unusual (opportunistic) infections
(2) Immune Dysregulation Disorders:
Autoimmune cytopenias (e.g., ITP)
Cancer predisposition
Eczema, severe allergies
Systemic autoimmunity (e.g., Lupus, vasculitis)
Enteropathy/Inflammatory bowel disease
What are the general treatment goals in managing ITP?
- Treat bleeding symptoms, not just the platelet count
- Improve quality of life
- Shared decision-making: Incorporate patient/family values and preferences
What are the first-line treatment options for ITP?
Observation (for mild cases)
IVIG (Intravenous immunoglobulin)
Corticosteroids
What are the second-line treatment options for ITP?
TPO-agents (Thrombopoietin receptor agonists)
Rituximab
Splenectomy
Why is immunology important in understanding human disease?
(1) Understanding immune pathways helps us understand human diseases better.
(2) Identifying which pathway, receptor, or gene is missing, defective, or overactive can help predict symptoms.
(3) Therapeutic targeting: Every immunologic pathway can potentially be targeted by therapies to treat diseases.
