Spontaneous perinephric hematoma due to acquired factor X deficiency in AL amyloidosis.

Spontaneous perinephric hematoma (SPH) is a rare entity whose diagnosis is challenging because of its varied clinical presentation and lack of any specific etiology. We report a 34-year-old African-American male who presented with left flank pain and was found to have a large left perinephric hematoma, in the setting of undiagnosed AL amylodosis. The case illustrates that while a SPH due to the vascular angiopathy of amyloid is rare, when amyloidosis is associated with abnormal coagulation studies or bleeding at multiple sites, it should be considered because of its protean systemic manifestations and potential response to chemotherapy.