Immune thrombocytopenia (ITP)

Background

Immune thrombocytopenia (ITP), also known as idiopathic thrombocytopenic purpura and immune thrombocytopenic purpura), is an autoimmune bleeding disorder where the body produces IgG autoantibodies against platelets, leading to their premature destruction (predominantly in the spleen) and impaired production in the marrow. In adults, it is usually chronic, whereas in children it's often acute and self-limiting.

Epidemiology

Incidence:

• Adults: Approximately 3-6 per 100,000/year
• Children: similar incidence; childhood cases more likely to spontaneously remit

Other epidemiology:

• Chronic ITP is most common in women aged 20–40.
• 75% of paediatric cases follow vaccination or infection (most commonly chickenpox or glandular fever).

Pathophysiology
IgG autoantibodies target platelet surface glycoproteins, most commonly GPIIb/IIIa and GPIb/IX, leading to opsonization and accelerated destruction of platelets, primarily in the spleen. It should be noted that in acute ITP non-specific immune complex attachment may occur rather than attachment of IgG autoantibodies.

Autoantibodies may also impair platelet production by affecting megakaryocytes in the bone marrow.

Dysregulation of T-cell immunity, including autoreactive cytotoxic T cells and reduced regulatory T-cell activity, further contributes to platelet destruction and reduced production.

Overall platelet lifespan may be reduced from around 10 days to just a few hours. Platelet turnover may increase up to 5-fold.

The net result is isolated thrombocytopenia, which manifests clinically as mucocutaneous bleeding, petechiae, and, in severe cases, hemorrhage, with bone marrow typically showing normal or increased megakaryocytes as a compensatory response.

Classification

ITP may be classified as primary or secondary based on cause. It may also be divided into acute and chronic forms.

• Primary (idiopathic) ITP: No underlying cause; isolated thrombocytopenia <100 × 10⁹/L
• Secondary ITP: Occurs in association with other conditions—e.g., SLE, CLL, HIV, HCV, drug reactions, or H. pylori infection.
• Acute ITP: very sudden onset, usually resolves within weeks to months.
• Chronic ITP: insidious onset, often relapsing and remitting.

Clinical presentation
Bleeding manifestations include:

• Petechiae
• Purpura and/or ecchymoses
• Gum or nose bleeds
• Menorrhagia
• Serious haemorrhage (≤10% in adults)

Children often present after viral illness and typically recover within weeks. Adults may have persistent thrombocytopenia, often asymptomatic or with mild bleeding. Splenomegaly is usually absent.

Diagnosis

Diagnosis is made via confirming isolated thrombocytopenia (platelet count <100 × 10³/microliter) without other abnormalities and excluding other causes.

Management

The treatment goal in ITP is to raise platelet count to a safe level, not necessarily to normalise it.

First-line:

• Corticosteroids (prednisone or high-dose dexamethasone)
• IVIG or anti-D immunoglobulin for severe bleeding or steroid-refractory cases

Second & Third-line:

• Splenectomy
• Rituximab
• Thrombopoietin receptor agonists e.g., romiplostim, eltrombopag
• Fostamatinib (a SYK inhibitor)

Prognosis

• Children: >80% of children with ITP recover on their own in six to twelve months regardless of whether they receive medication. Approximately 70% resolve within 6 months.
• Adults: Remission in 20–40%; many remain dependent on long-term therapy but maintain bleeding control.

Summary table