BACKGROUND: Calciphylaxis combines features of vascular thrombotic occlusion and 
endoluminal calcification. In this study we examine the expression of 
osteopontin as a diagnostic marker and its role in lesional pathogenesis.
METHODS: 25 formalin-fixed, paraffin embedded skin biopsies of 20 females and 5 
males (mean age of 60 years) with a diagnosis of calciphylaxis were assessed for 
osteopontin expression.
RESULTS: Lower extremities were the most commonly involved areas; however a 
truncal and genital distribution was also noted in 3 cases. Renal failure was 
present in 21 of 25 cases. One patient had myeloproliferative disorder and one 
patient had advanced colon cancer. The dominant pathology was localized to the 
subcutaneous fat, characterized by mural calcification and luminal thrombosis 
affecting capillaries, venules, arterioles and small arteries. In 2 cases, a 
subcutaneous thrombogenic vasculopathy without calcification was noted. 
Osteopontin expression was confined to the subcutis, being most striking in 
calcified vessels but also apparent in vessels without calcification, including 
mineral poor variants of calciphylaxis.
CONCLUSION: Calciphylaxis represents a unique calcific thrombogenic 
vasculopathy, not limited to renal failure. Ectopic osteopontin expression may 
define a critical and initial event in the calciphylaxis pathogenesis. 
Therapeutic agents designed to reduce osteopontin expression may be of value in 
its treatment.