Scurvy's Bleeding: A Paradox Explained
Scurvy, a severe vitamin C deficiency, has long been associated with hemorrhagic manifestations, such as bleeding gums, petechiae, and ecchymoses. A common assumption might be that such bleeding implies a prolonged bleeding time. However, the standard bleeding time test, which measures the time it takes for a small incision to stop bleeding, actually remains normal in scurvy. This surprising result clarifies the core pathophysiology of the disease, pointing away from a primary coagulation disorder and toward a fundamental defect in blood vessel integrity.
The Misconception: Why Bleeding Time Is a Misleading Indicator
The bleeding time test is a historical method used to assess primary hemostasis, specifically the function of platelets and the initial formation of a platelet plug at the site of a small vascular injury. A prolonged bleeding time typically indicates a problem with platelet function (e.g., in conditions like von Willebrand disease) or a low platelet count (thrombocytopenia). The fact that bleeding time is normal in scurvy reveals that, for the most part, platelet number and function are unaffected by a lack of vitamin C. This is a crucial distinction that has led to the test being largely superseded by more specific and sensitive assays today.
The Core Problem: Defective Collagen Synthesis
The true cause of bleeding in scurvy lies in the critical role vitamin C plays in collagen synthesis. Vitamin C, or ascorbic acid, is a necessary cofactor for the enzymes prolyl hydroxylase and lysyl hydroxylase. These enzymes hydroxylate the amino acids proline and lysine, a step that is essential for the formation of stable, cross-linked collagen fibrils. Collagen is the most abundant structural protein in the body, providing strength and integrity to connective tissues, including the walls of capillaries and larger blood vessels.
Without sufficient vitamin C, the collagen produced is weak, unstable, and unable to properly support the vascular walls. This defective connective tissue leads to structurally fragile capillaries that easily rupture under normal blood pressure, causing blood to leak into surrounding tissues. This mechanism explains the characteristic petechial and perifollicular hemorrhages seen in scurvy, especially in dependent areas like the legs, where hydrostatic pressure is greatest.
Platelet Function and Coagulation in Scurvy
While some older research may have suggested an impact on platelet function, a comprehensive experimental study found that platelet number, aggregation response, and glass bead retention were all normal in subjects with induced vitamin C deficiency. The study concluded that mucocutaneous hemorrhage in scurvy is not a result of impaired platelet function. The broader coagulation cascade, which is assessed by tests like prothrombin time (PT) and activated partial thromboplastin time (aPTT), also typically remains unaffected in scurvy. This is because vitamin C is not directly involved in the synthesis or activation of the specific clotting factors that comprise these pathways, unlike vitamin K.
Scurvy vs. Platelet Disorder: A Comparison
| Feature | Scurvy (Capillary Fragility) | Platelet Disorder (e.g., Thrombocytopenia) |
|---|---|---|
| Bleeding Time Test Result | Normal | Prolonged |
| Underlying Cause | Defective collagen leading to weakened capillary walls | Abnormal platelet count or function |
| Mechanism of Bleeding | Structural failure of blood vessel walls | Failure to form a proper platelet plug at the site of injury |
| Classic Bleeding Symptoms | Perifollicular hemorrhages, ecchymoses, bleeding gums | Petechiae, purpura, easy bruising, spontaneous bleeding |
| Platelet Count | Typically normal | Low |
Conclusion: The Bigger Picture of Scurvy
The most important takeaway is that the bleeding associated with scurvy is a vascular problem, not a platelet or coagulation problem. The normal bleeding time test is a historical but informative finding that reinforces this distinction. Vitamin C deficiency's impact on collagen synthesis leads to widespread capillary fragility, which is the direct cause of the hemorrhages and other tissue-related symptoms. With treatment, which involves vitamin C supplementation, capillary stability can be rapidly restored, and bleeding stops within 24 hours in many cases. This highlights the critical role of adequate vitamin C intake in maintaining healthy connective tissues and preventing hemorrhagic disease.
For more information on the pathophysiology and treatment of vitamin C deficiency, see the Medscape overview of scurvy.(https://emedicine.medscape.com/article/125350-overview)
