Vascular bleeding disorders
- Lesion
When the small vessels themselves are weak, the skin and mucosa bleed even though platelets and clotting tests are normal.
What it is
Vascular bleeding disorders are common but rarely severe. They cause petechiae and purpura of skin and mucous membranes with normal platelet counts and clotting tests. Mechanisms include infections that damage endothelium (meningococcaemia, rickettsiae, infective endocarditis), immune-complex vasculitis caused by drugs or IgA, defective collagen (scurvy, Ehlers–Danlos syndrome), loss of supporting tissue (old age, glucocorticoid excess), malformed vessels (hereditary haemorrhagic telangiectasia) and amyloid infiltration of vessel walls.
Structure
- Telangiectasias: dilated, thin-walled capillaries and venules lined by a single endothelial layer.
- Leukocytoclastic vasculitis: fibrinoid necrosis of venules, neutrophils and nuclear dust, red cell extravasation; IgA deposits in IgA vasculitis.
- Scurvy: poorly formed collagen around vessels and hair follicles with haemorrhage.
Step by step
- Endothelium is damaged (infection, immune complexes) or the vessel support is weak (collagen, amyloid, atrophy).
- Small vessels rupture with ordinary pressures or minor trauma.
- Red cells leak into skin and mucosa: petechiae, purpura, ecchymoses.
- Platelet and coagulation function are intact, so bleeding is usually limited.
- Malformed vessels (HHT) bleed repeatedly from exposed surfaces, causing iron deficiency.
Causes of vascular purpura
| Cause | Mechanism | Key features |
|---|---|---|
| Scurvy | Defective collagen hydroxylation | Perifollicular haemorrhage, gum bleeding |
| Ehlers–Danlos syndrome | Inherited collagen defects | Easy bruising, hyperelastic skin, joint laxity |
| Cushing syndrome and old age | Loss of perivascular support | Senile purpura on forearms, thin skin |
| IgA vasculitis | IgA immune-complex vasculitis | Palpable purpura, abdominal pain, arthritis, nephritis |
| Hereditary haemorrhagic telangiectasia | Malformed thin vessels and arteriovenous malformations | Epistaxis, GI bleeding, lung and brain AVMs |
| Amyloidosis | Amyloid in vessel walls | Periorbital purpura, macroglossia |
Clinical notes
- Fever with spreading petechiae suggests meningococcaemia, an emergency.
- Drug-induced hypersensitivity vasculitis is a common cause of purpura without thrombocytopenia.
Test yourself
Think of the answer, then tap the question to see it.
Which blood tests are abnormal in vascular bleeding disorders?
Usually none: platelet count, PT and PTT are normal.
Which genes are involved in hereditary haemorrhagic telangiectasia?
Genes of the TGF-β signalling pathway, such as endoglin (ENG) and ACVRL1.
Why does scurvy cause bleeding?
Vitamin C is needed to hydroxylate collagen; weak collagen fails to support small vessels.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Hereditary hemorrhagic telangiectasia: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Bleeding Disorders | MedlinePlus (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.