Assessment and diagnosis
Most important for the diagnosis is the detection of amyloid in a relevant biopsy, followed by classification of the type of amyloid protein.
The below photo shows amyloid accumulation in glomerulus, demonstrated using Congo Red staining. The apple-green fluorescence is characteristic. It appears when using microscopy in polarized light.
Optimally, the biopsy will be from a suspected, involved organ, but in case of clear signs of systemic amyloidosis, the detection of amyloid and type classification can be based on a biopsy from a more “accessible” area, e.g. subcutaneous fat biopsy, bone marrow or rectum. It is, however, essential that the type of amyloid is determined. It is thus a potential error source that in patients with established amyloid in a biopsy, subsequently M-component can be detected in serum or urine, and that this is then interpreted as sufficient basis for an AL amyloidosis diagnosis. Small M components and imbalance in the free light chains can randomly be detected in upwards of 10% of the older population.
Immunohistochemical characterization of the amylogenic protein is often difficult and uncertain. More reliable methods are immune electron microscopy and mass spectrometric characterization.
At AmyC OUH, diagnostics are, whenever possible, based on biopsy material from the clinically involved organ, and a cut is made of the amyloid using laser dissection microscopy with subsequent mass spectrometric characteristic of the protein. Immune electron microscopy is also established and used subsequent to a specific assessment.
If the detected amyloid protein can be associated with hereditary illness, a clinical genetic analysis is performed along with relevant genetic counselling of patients and their families.
I case of verified amyloidosis, careful screening for involved organs is required. This is performed according to a fixed procedure and means, at AmyC OUH, a multidisciplinary approach to the patient. As cardiac involvement requires special prognostics and treatment, a particularly careful echocardiographic assessment is performed – often with the use of additional functional and imaging techniques, including an MR scan of the heart.