Case Presentation:

A 64 year old man with past medical history of end stage renal disease (ESRD) on hemodialysis (HD) for 11 years, type II diabetes mellitus, HIV on highly active antiretroviral therapy, and recently identified right toe infection presented with sudden onset of severe right hip pain. Two weeks prior to presentation he had been seen in the ED for possible right toe osteomyelitis and had completed a course of Augmentin. During that visit, he had no known hip pain and was able to bear weight on his right foot.

At presentation, his physical exam was significant for tenderness over lateral right hip, inability to bear weight, pain with active range of motion, and a right necrotic great toe. He reported no recent trauma to the affected limb. The Orthopedic service was consulted and recommended MRI of right hip.

The MRI of the right hip revealed capsular and synovial thickening with extensive erosive changes of the right femoral neck with high and low signal intensity infiltrates compatible with amyloidosis involving greater than 50% of the shaft and concerning for an impending pathological fracture. An abdominal fat pad biopsy was negative for amyloid. However, serum β2 microglobulin was elevated at 20 times the upper limit of normal.  Total protein was mildly elevated, serum protein electrophoresis showed a normal electrophoretic pattern. He underwent right hip hemiarthroplasty. Pathology revealed Congo red stain positive deposits consistent with nodular amyloid deposition.

Discussion:

Dialysis related amyloidosis (DRA) is associated with infiltrative osteoarticular lesions. Risk factors for DRA include older age, duration of dialysis, and type of dialysis membrane.1 Although the exact pathogenesis is unknown, it is likely that decreased glomerular filtration rate in ESRD leads to elevated levels of serum β2 microglobulin.  β2 microglobulin amyloid (Aβ2M) fibrils are created in the setting of inflammation and deposit in tissue leading to carpal tunnel syndrome, destructive joint arthropathy, and lytic bone lesions. Post-mortem studies demonstrate that, after 7 years on HD, 90% of patients on HD have Aβ2M deposits.2 Aβ2M leads to destruction of normal bone architecture and lytic lesions, most commonly in the femoral neck, C1-C2 vertebra, and scaphoid bone. Notably, progression of disease correlates to time on HD. Treatment of femoral neck amyloidosis is total joint replacement. HIV infection is also associated with elevated serum β2 microglobulin and may have contributed to this presentation. Despite a high initial suspicion for septic hip joint, our patient was at increased risk for DRA joint arthropathy given an 11-year history of HD, elevated serum Aβ2M, and suspicious findings on MRI that were later confirmed by pathology.

 Conclusions:

DRA can cause cystic hip lesions and consequent pathological fractures. In patients on HD presenting with hip pain, amyloidosis should be considered.

  1. Davison AM. beta 2-microglobulin and amyloidosis: who is at risk?. Nephrol Dial Transplant. 1995;10 Suppl 10:48-51.

  2. Jadoul, Michel, et al. “Histological prevalence of β2-microglobulin amyloidosis in hemodialysis: A prospective post-mortem study.” Kidney international 51.6 (1997): 1928-1932.