Dr Isobel Yeap1, Dr Aruna Wijewardana1, Dr John Vandervord1
1Royal North Shore Hospital, St Leonards, Australia
Factor XII deficiency has an estimated incidence of 1-3%. For many years, it was believed to be unique amongst the factor deficiencies in the sense that it was thought to have no clinical significance. It is typically diagnosed incidentally on pathology tests: ex vivo it causes a prolongation of partial thromboplastin time (PTT), but in vivo it has been shown to have no effect on haemostasis. Large-scale human studies have proven contradictory. Some studies have suggested an inverse association between factor XII levels and risk of myocardial infarction, while other have suggested that factor XIIa may contribute to thrombus formation.
We present an interesting case of a patient with Factor XII deficiency who presented with a 13% burn to her forearm, face and abdomen due to smoking in bed. She was taken to the operating theatre eight times for repeated debridement and application of split thickness skin grafts. Due to significant post-operative bleeding, her haemoglobin dropped to 57. She required regular blood transfusions, in total receiving 22 units of packed red blood cells.
Recent studies involving murine models have shown that mice with Factor XII deficiency have impaired formation of thrombi in arterial injury models. Burns surgery involves extensive and repeated debridement of dermal skin, which is rich in capillaries, venules and arterioles. We propose that our patient may have been unable to achieve adequate haemostasis of the small vessels sheared during debridement, such that her Factor XII deficiency may have been responsible for her delayed but significant post-operative oozing.
Isobel is a resident medical officer who has worked with the Severe Burns Unit and Plastic Surgery Department at Royal North Shore Hospital. Prior to studying medicine, she completed her Bachelor (Honours) in Economics.