Protein S deficiency: early presentation and pulmonary hypertension

Protein S deficiency usually presents in adults with recurrent or unexplained thrombosis and is thought to have autosomal dominant inheritance. We describe the case of a 5 year old girl with pulmonary hypertension but no evidence of venous thrombosis until postmortem examination. Her parents were first cousins. This potentially treatable condition should be sought in children and their relatives screened.