How amyloidosis can present with swollen shoulders

An interesting case courtesy of this week’s NEJM:

A 66-year-old man presented with a two-year history of fatigue, paresthesia of the legs and feet, weight loss, and shoulder enlargement, with limitation of movement. On physical examination, periorbital ecchymoses (the “raccoon” sign) and infiltration of the periarticular tissues of the shoulders were found.

A biopsy specimen of abdominal fat that was stained with Congo red was positive for amyloid, and serum monoclonal paraprotein (lambda light chain) was detected by immunoelectrophoresis.

Amyloidosis is a disorder where insoluable protein fibers are deposited into tissues and organs, impairing their function. The heart, kidneys, liver, skin, lungs, and muscle can all be affected.

The “shoulder pad” sign is an enlargement of the anterior shoulder due to fluid in the joint and/or amyloid infiltration of the synovial membrane and surrounding structures. This type of soft tissue swelling can occur in up to 75% of amyloid cases.

The following X-ray demonstrates the shoulder pad sign (from UptoDate):