CLOTS AND CRACKS

OSTEOPOROSIS AS A CONSEQUENCE OF PROTEIN C DEFICIENCY AND WARFARIN USE

Abstract

INTRODUCTION/BACKGROUND
Activated protein C is essential in anticoagulation. Protein C deficiency results in inappropriate blood clot formation due to dysregulated coagulation. We report a case of osteoporosis secondary to protein C deficiency and warfarin use.

CASE
A 30-year-old male initially presented with a superior sagittal sinus thrombosis, complicated with a left frontal lobe venous infarct at the age of 21. He reported a family history significant for venous thromboembolism. A thrombophilia screen done during presentation revealed a moderately low protein C activity at 44.6% (reference interval 70–140) with normal protein S levels. Autoimmune workup including anticardiolipin, and lupus anticoagulants were negative. Long-term warfarin was initiated for the treatment of the cerebral venous thrombosis (CVT).

Three years after CVT and warfarin use, old compression fractures involving the T5 and T7 vertebrae were found on routine X-rays done during an admission for rhabdomyolysis. A bone mineral densitometry (BMD) showed a Z score of -2.8 at the femoral neck, and -1.5 at the L1-L4 vertebrae. Screening for causes of secondary osteoporosis, specifically hyperparathyroidism, hyperthyroidism, hypogonadism, acromegaly, chronic kidney disease, and Cushing syndrome were negative. The patient’s inability to attain peak bone mass would likely be due to severe illness (CVT) suffered at a young age.

Upon diagnosis of osteoporosis, warfarin was replaced with rivaroxaban for anticoagulation and vitamin D replacement and calcium supplements were started, while no anti-osteoporosis medications were initiated. Annual BMD was done, and the latest imaging showed an improvement of 2.4% in the femoral neck compared to the previous year. Apart from the previously noted vertebral compression fractures, no new fractures were appreciated during follow-up. BMD monitoring will continue every 2 years.

CONCLUSION
Osteoporosis in the young should be thoroughly investigated and managing the underlying condition is key to proper treatment.