Systemic amyloid A amyloidosis secondary to presumed chronic vertebral osteomyelitis and pressure ulcers in a mandrill (Mandrillus sphinx)

Systemic amyloid A (AA) amyloidosis involves extracellular deposition of fibrils derived from serum amyloid A (SAA) and is typically associated with chronic inflammation. A 16-year-old male mandrill (Mandrillus sphinx) developed lameness and presumed chronic vertebral osteomyelitis, progressed to recumbency, and died. Histopathology revealed Congo red-positive deposits with apple-green birefringence under polarized light in multiple organs, including the liver, spleen, kidneys, heart, and intestines. Immunohistochemistry confirmed SAA immunoreactivity, and mass spectrometry identified SAA-2 as the predominant amyloid protein, establishing systemic AA amyloidosis. No infectious agents were detected in examined tissues; however, vertebral osteomyelitis and pressure ulcers were considered likely sources of persistent inflammation, which may have contributed to the development of systemic AA amyloidosis. This represents the first reported case of amyloid AA amyloidosis in a mandrill, in which amyloid A was identified and confirmed by both immunohistochemistry and mass spectrometry.