Pitfalls in the diagnosis of primary amyloidosis.

Primary (AL) amyloidosis is the most prevalent type of systemic amyloidosis, and management of this disease has evolved through the years from supportive care to aggressive treatments that include immunomodulatory agents and high-dose chemotherapy with hematopoietic stem cell transplantation. However, other types of amyloidosis are increasingly recognized, such as familial amyloidosis and senile cardiac amyloidosis, and management of these conditions is different from that of AL amyloidosis. Congo red staining with exhibition of an apple-green birefringence is diagnostic of amyloid. Immunohistochemistry can detect amyloid deposits but has limitations, and newer molecular techniques such as mass spectrometry show promise in determining types of amyloidosis. Physicians need to be aware of clinical scenarios that can mimic AL amyloidosis to avoid misdiagnosis and harm to the patient.