How is AL amyloidosis primarily diagnosed?

AL amyloidosis, a condition characterized by the deposition of amyloid protein resulting from immunoglobulin light chains, is primarily diagnosed through a histological examination that involves Congo red staining. This specific staining method is crucial because it highlights amyloid deposits in tissues with a characteristic apple-green birefringence under polarized light. This histological confirmation is essential for diagnosing amyloidosis, differentiating it from other conditions that may present with similar symptoms.

While other methods, such as blood tests, can provide supporting evidence by detecting abnormal free light chains, they are not definitive for the diagnosis of AL amyloidosis on their own. Imaging techniques like X-rays are primarily used to assess organ involvement or complications rather than to identify amyloid deposits directly. Hence, a histological examination with Congo red staining remains the gold standard for confirming the presence of amyloid in tissue samples.