Clinical Images in Nephrology and Dialysis
Case Answer
A 27 year-old woman with hypertension, focal glomerular sclerosis, and ESKD had been on in-center hemodialysis for 4 years. Her monthly laboratory values revealed persistent elevation of the serum intact parathyroid hormone (PTH) (1500 pg/ml), despite dietary phosphate restriction, phosphate binders, and high doses of paricalcitol. During the previous year, she had missed several scheduled surgery appointments for a parathyroidectomy.
While walking down stairs, the patient fell, immediately experienced severe bilateral knee pain, and was unable to stand up. She was seen in the emergency room, where she was noted to have moderate bilateral knee swelling and inability to extend her legs. A radiograph of the knees showed no evidence of fracture, and the patient was prescribed narcotic analgesics.
The bilateral knee pain persisted for several days, and she was unable to bear weight. When she saw her nephrologist a few days later, she had persistent bilateral knee swelling and severe pain on attempted leg extension. Pertinent laboratory values included: serum phosphorus 10.5 mg/dl, serum calcium 9.6 mg/dl, PTH 2004 pg/ml, and alkaline phosphatase 767 IU/L.
She was admitted to the hospital where she underwent a total parathyroidectomy and bilateral knee surgery (Figure 1). Postoperatively, she had external plastic splints placed for 2 weeks to immobilize the knees. After several weeks of vigorous physical therapy, she was able to ambulate without difficulty. The repeat serum PTH was 12 pg/ml.
Figure 1.
Clinical images case for K360. Surgical scars in the knees and neck for this patient.
Discussion
Secondary hyperparathyroidism is a common complication in patients with secondary hyperparathyroidism. Severe cases may result in pathologic bone fractures, vascular calcification, or refractory anemia. Nontraumatic patellar tendon rupture is a rare complication of severe secondary hyperparathyroidism in patients on dialysis (1,2). The mechanism is thought to be due to severe bone resorption at the site of tendon insertion. Flexion of the knee during minor activity can cause the patellar ligament to snap acutely at its insertion site in the kneecap. The presenting symptoms include acute knee pain and inability to extend the leg or bear weight. Magnetic resonance imaging is useful in visualizing the anatomic abnormality. Definitive therapy requires surgically reconnecting the patellar ligament to the kneecap, in conjunction with parathyroidectomy to alleviate renal osteodystrophy. Rupture of other lower extremity tendons, including the quadriceps and Achilles tendon, has also been described in patients with severe secondary hyperparathyroidism who are on dialysis.
Teaching Points
If a dialysis patient with severe secondary hyperparathyroidism develops acute knee pain and inability to extend the leg in the absence of trauma, you should suspect a patellar tendon rupture.
Magnetic resonance imaging is the diagnostic test of choice for potential patellar tendon rupture.
Disclosures
M. Allon reports personal fees from CorMedix outside of the submitted work.
References
- 1.Chen CM, Chu P, Huang GS, Wang SJ, Wu SS: Spontaneous rupture of the patellar and contralateral quadriceps tendons associated with secondary hyperparathyroidism in a patient receiving long-term dialysis. J Formos Med Assoc 105: 941–945, 2006 [DOI] [PubMed] [Google Scholar]
- 2.Kalantar-Zadeh K, Singh K, Kleiner M, Jarrett MP, Luft FC: Nontraumatic bilateral rupture of patellar tendons in a diabetic dialysis patient with secondary hyperparathyroidism. Nephrol Dial Transplant 12: 1988–1990, 1997 [DOI] [PubMed] [Google Scholar]