Abstract
Factor XIII (FXIII) deficiency is a rare coagulopathy with an estimated prevalence of approximately 1 in 1 to 2 million, affecting males and females with equal frequency. FXIII plays a critical role in hemostasis by stabilizing fibrin clots through covalent cross-linking of fibrin monomers, thereby conferring mechanical resistance and durability to the clot structure. Clinically, FXIII deficiency presents with a spectrum of hemorrhagic manifestations including bleeding from the umbilical cord, intracranial hemorrhage, recurrent miscarriages, menorrhagia, epistaxis, gingival bleeding, and poor wound healing. Despite significant bleeding symptoms, routine primary hemostasis screening tests are typically within normal limits since FXIII acts downstream of clot formation. The clot solubility in 5-molar urea is widely used, especially in resource-limited settings. An 11-year-old female patient presented with symptoms including vomiting, lethargy, severe headache, and a subgaleal hematoma. Neurosurgical intervention confirmed intracranial hemorrhage. Her medical history was notable for neonatal umbilical cord bleeding, hematomas, and postdental extraction bleeding. Despite these clinical features, multiple clot solubility tests yielded normal results. Subsequent quantitative assessment of FXIII by chromogenic assay performed on the CS-5100 system revealed a markedly decreased FXIII activity level of 12.4%. This discrepancy highlights the limited insensitivity of the clot solubility test in detecting FXIII deficiency. Therefore, accurate diagnosis of FXIII deficiency necessitates a combined diagnostic approach incorporating both clot solubility testing and specific quantitative FXIII activity measurement. The clot stability test, despite its limitations in detecting FXIII deficiency, is frequently employed in developing countries for screening reduced FXIII levels due to its simplicity. However, the current findings indicate that in patients suspected of FXIII deficiency, accurate diagnosis necessitates the performance of both a clot stability test (5 M urea test) and a specific FXIII activity assay. A comprehensive medical and family history is fundamental to the clinical and laboratory approach to patients presenting with bleeding tendencies. Notably, a subset of patients exhibiting bleeding symptoms may exhibit normal findings on initial first-line hemostasis screening assays.