Heart failure in hypophosphatemic rickets: complications from high-dose phosphate therapy

To report a rare case of hypophosphatemic rickets (HR) leading to extensive cardiac complications.

We present the clinical course and autopsy findings of a patient with HR, treated with chronic phosphate-only therapy as a child, who subsequently developed tertiary hyperparathyroidism leading to extensive cardiac calcifications and complications. We also review the literature on the pathophysiology of calcifications from HR.

A 34-year-old man was diagnosed with HR at 4 years of age after presenting with growth delay and leg bowing. Family history was negative for the disease. He was initiated on high-dose phosphate therapy (2-6 g of elemental phosphorus/day) with sporadic calcitriol use between 4-18 years of age. For 6 years he received phosphate-only therapy. Subsequently, he developed nephrocalcinosis, heart valve calcifications, severe calcific coronary artery disease, heart block, and congestive heart failure. At a young age, he required an aortic valve replacement and a biventricular pacemaker that was subsequently upgraded to an implantable cardioverter defibrillator. Autopsy showed extensive endocardial, myocardial, and coronary artery calcifications.

Cardiac calcification is a known sequela of tertiary hyperparathyroidism when it occurs in patients with renal failure, but it is rarely seen in HR due to high phosphate therapy. Phosphate alone should never be used to treat HR; high doses, even with calcitriol, should be avoided. It is important to be cognizant of high-dose phosphate effects and to consider parathyroidectomy for autonomous function, if needed. This case emphasizes the importance of appropriate therapy, monitoring, and management of patients with HR.