Glycoprotein VI deficiency

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Glycoprotein VI deficiency is a bleeding disorder associated with a decreased ability to form blood clots. Normally, blood clots protect the body after an injury by sealing off damaged blood vessels and preventing further blood loss. Because people with glycoprotein VI deficiency cannot form blood clots normally, they have an increased risk of nosebleeds (epistaxis) and may experience abnormally heavy or prolonged bleeding following minor injury or surgery. In some affected individuals, spontaneous bleeding under the skin causes areas of discoloration (ecchymosis). Women with glycoprotein VI deficiency often have heavy or prolonged menstrual periods (menorrhagia).

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Glycoprotein VI deficiency can be caused by mutations in the GP6 gene, which provides instructions for making a protein called glycoprotein VI (GPVI). This protein is embedded in the outer membrane of blood cells called platelets, which are an essential component of blood clots. In response to an injury that causes bleeding, the GPVI protein begins clot formation by attaching (binding) to another protein called collagen that is found on blood vessel walls. The binding of GPVI to collagen also signals additional platelets to come together to increase the size of the clot.

GP6 gene mutations can lead to the production of no GPVI protein; an abnormally short, nonfunctional GPVI protein; or a protein that is less able to bind to collagen. Without GPVI binding to collagen, platelets cannot come together efficiently to form a clot, leading to the bleeding problems associated with glycoprotein VI deficiency.

Some cases of glycoprotein VI deficiency are not caused by GP6 gene mutations; instead these cases are acquired, which means they do not appear to be caused by inherited gene mutations. These acquired cases of glycoprotein VI deficiency are associated with autoimmune disorders such as immune thrombocytopenia purpura, Graves' disease, or systemic lupus erythematosus (SLE). Autoimmune disorders occur when the immune system malfunctions and attacks the body's own cells and tissues. Some individuals with these autoimmune disorders produce immune proteins called antibodies that attack and destroy the GPVI protein. As a result, there is a shortage (deficiency) of functional GPVI protein on the surface of platelets, which leads to bleeding problems characteristic of glycoprotein VI deficiency.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

When this condition is caused by mutations in the GP6 gene, it is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

The prevalence of glycoprotein VI deficiency is unknown. At least 15 cases have been described in the scientific literature.

Understanding terms used in the source

These definitions explain medical words used above. A definition is not evidence that another condition is present, and it does not predict how a symptom will develop. Ask the clinician which terms apply to the actual examination or test result.

Systemic lupus erythematosus

A chronic, relapsing, inflammatory, and often febrile multisystemic disorder of connective tissue, characterized principally by involvement of the skin, joints, kidneys, and serosal membranes.

Menorrhagia

Prolonged and excessive menses at regular intervals in excess of 80 mL or lasting longer than 7 days.

Prolonged

Applied to an abnormality whose duration is extended over a longer period of time than is expected or usual (e.g., prolonged fever lasts longer than one usually sees with an infection).

Affected

This term applies to a family member who is diagnosed with the same condition as the individual who is the primary focus of investigation (the proband).

Purpura

Purpura (from Latin: purpura, meaning purple) is the appearance of red or purple discolorations on the skin that do not blanch on applying pressure. They are caused by bleeding underneath the skin. This term refers to an abnormally increased susceptibility to developing purpura. Purpura are larger than petechiae.

Which doctor should you see?

The suggested department for discussing Glycoprotein VI deficiency is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Glycoprotein VI deficiency. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.