ABSTRACT
INVESTIGATIONS The differential diagnosis depends on the type of amyloidosis considered. For primary amyloidosis, pinch purpura may be mimicked by senile purpura, anticoagulant medications, or clotting/platelet abnormalities. It is an important condition to diagnose, since it has many systemic manifestations. Skin biopsy is helpful if positive, but cannot exclude the diagnosis. Fat aspiration or rectal biopsy has a higher yield but is more difficult to perform. Serum and urine protein electrophoresis studies can detect abnormal proteins.
