Factor XIII A-subunit (Specialist drug)

How it works

It replaces the deficient factor XIII A-subunit, restoring the transglutaminase that cross-links fibrin to stabilise the clot and protect it from premature breakdown.

Prescribing in practice

• Inhibitory antibodies to factor XIII can develop and reduce efficacy, so loss of response should prompt inhibitor testing under specialist supervision.
• It replaces only the A-subunit and is therefore not suitable for the rare B-subunit deficiency, so the deficiency type must be confirmed before use.
• Hypersensitivity and, rarely, thromboembolic events can occur, and viral-safety considerations apply to factor products.

Monitoring

Monitor factor XIII activity levels to guide prophylactic dosing and screen for inhibitors if breakthrough bleeding occurs.

Counselling the patient

• Report new or breakthrough bleeding despite regular treatment, as this may indicate an inhibitor.
• Report any allergic-type reaction during or after administration.
• Attend scheduled reviews so factor levels can be checked and prophylaxis adjusted.

Evidence & guidelines

Replacement therapy is the established approach for congenital factor XIII deficiency, managed within specialist haemophilia and bleeding-disorder centres.