Résumé
Patients with hypothyroidism may have a minor increase in their bleeding tendency, causing easy bruising and menorrhagia. There is a positive correlation between factor VIII coagulant activity and thyroxin serum levels. Thus, patients with hypothyroidism have an acquired coagulation defect that is reversible with thyroxin supplementation. We report two sisters, aged 13 and 11 years, who met the criteria for von Willebrand's disease at the age of eight. Both sisters had a primary hypothyroidism due to Hashimoto's thyroiditis, diagnosed three years later. Thyroid hormone replacement normalized von Willebrand factor, factor VIII, and the bleeding diathesis disappeared. Acquired von Willebrand's disease is an unusual manifestation of hypothyroidism. However the possibility of hypothyroidism should be considered in patients presenting with von Willebrand disease.