CONSTITUTIONAL PROTHROMBIN DEFICIENCY REVEALED BY A FAMILY INVESTIGATION

Congenital prothrombin (factor II) deficiency is an extremely rare inherited coagulation disorder transmitted in an autosomal recessive manner and characterized by wide clinical variability, ranging from mild bleeding manifestations to life threatening hemorrhage. We report a familial case of severe congenital factor II deficiency diagnosed in the hematology laboratory of the Mohammed V Military Teaching Hospital in Rabat. The index case was a 6 year old girl born to a second degree consanguineous marriage, referred for cutaneous bleeding manifestations associated with recurrent knee pain, in a context of prolonged activated partial thromboplastin time and reduced prothrombin time. Coagulation studies revealed an isolated and severe reduction in factor II activity to 3%, with normal levels of the other coagulation factors.Family investigation identified a similar severe deficiency in both brothers, with variable hemorrhagic manifestations, whereas the parents were asymptomatic and exhibited moderately reduced factor II activity, consistent with a heterozygous carrier state.The combination of clinical and biological findings supported the diagnosis of severe constitutional factor II deficiency, most likely type I. This case highlights the importance of family investigation and consideration of consanguinity in the diagnosis of rare bleeding disorders, and underscores the central role of the laboratory in early identification, patient management, and genetic counseling.