Immune thrombocytopenia

Classification and triggering factors

Although primary immune thrombocytopenia is idiopathic in nature (the exact cause cannot be determined), specialists identify a number of triggers that frequently precede the manifestation of the disease. These include past or persistent infections (bacterial agents, cytomegalovirus, Epstein-Barr virus, adenovirus), drug effects (use of paracetamol, diuretics, and sulfonamides), and vaccination (predominantly against measles and rubella).

According to the international consensus of 2010, the pathology is classified by the duration of the course:

• Acute ITP: newly diagnosed episode lasting less than 3 months.
• Persistent ITP: disease persists from 3 to 12 months.
• Chronic ITP: duration of thrombocytopenia exceeds 12 months.

Pathogenesis: how platelets are destroyed

The disease is based on accelerated platelet destruction, which inevitably impairs normal vascular hemostasis. Specific immune complexes settle on the membranes of blood platelets. These "tagged" cells are sent to the spleen, where macrophages immediately recognize and destroy them.

Platelet deficiency triggers a cascade of endothelial dysfunction and leads to bleeding:

1. The physiological "marginal pooling" of platelets along the vessel wall disappears.
2. The angiotrophic function is lost—the vascular wall is deprived of adequate nutrition.
3. There is a sharp drop in serotonin levels, which are normally released by blood platelets, causing vessels to lose their contractility.
4. Due to endothelial weakness, erythrocytes freely penetrate into surrounding tissues, forming ecchymoses (bruises).

Clinical presentation: dry and wet purpura

The severity of symptoms directly depends on the degree of thrombocytopenia. If the cell count remains above 30 × 10⁹/L, "dry" purpura develops, limited exclusively to the cutaneous hemorrhagic syndrome. With a further drop in parameters, "wet" purpura occurs, involving the mucous membranes (especially the hard and soft palate) and sclera. Retinal hemorrhages are particularly hazardous as they threaten vision loss.

The thrombocytopenic (petechial-macular) type of bleeding is characterized by specific features of the rash:

• Spontaneity: they appear without physical impact or trauma.
• Painlessnes: the patient experiences no discomfort.
• Polymorphism: small petechiae (2–3 mm), larger elements (4–5 mm), and extensive ecchymoses are visible simultaneously.
• Polychromia: elements have different shades due to the staged breakdown of pigments (conversion of bilirubin to biliverdin).
• Asymmetry: chaotic arrangement without favored localizations.

Localization of bleeding and organ lesions

Massive bleeding in "wet" purpura poses a threat of developing secondary posthemorrhagic anemia. The most frequent localizations of hemorrhages include:

• Uterine bleeding (menorrhagia) — 80–85% (most typical for the pubertal period in girls).
• Nosebleeds (epistaxis) — 35–40%.
• Gum bleeding — 15–20%.
• Gastrointestinal bleeding — 10–15%.
• Renal bleeding (hematuria) — 7–10%.

Internal organ involvement is not a typical sign of ITP, but if it occurs, the prognosis worsens sharply. The development of hemorrhagic stroke (cerebral hemorrhage) is accompanied by intense headache, vomiting, seizures, and leads to persistent neurological deficit. Bilateral adrenal hemorrhage can provoke acute adrenal insufficiency.

Stages of the chronic course and remission

Chronic immune thrombocytopenia proceeds cyclically and includes 3 periods. The first period is a hemorrhagic crisis, accompanied by vivid clinical symptoms, a profound drop in platelets, and prolonged bleeding time.

Outside of a crisis, the patient's condition is evaluated by the level of normalization of parameters:

• Clinical remission: visually, there is no bleeding or bruising, but thrombocytopenia persists in lab tests, bleeding time is prolonged, and endothelial tests (pinch and tourniquet tests) remain positive.
• Clinical and hematological remission: complete recovery with no clinical symptoms and no laboratory abnormalities.

Class and exam questions

What else to study on this topic

• Clinical characteristics of the 2nd and 3rd periods of chronic ITP
• Methodology for performing and evaluating endothelial tests (tourniquet and pinch tests)
• Pathogenesis of secondary posthemorrhagic anemia against the background of profuse bleeding
• Management tactics for adolescent girls with uterine bleeding in ITP

Other topics in "Chapter 10. Diseases of the Blood and Blood-Forming Organs"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.