Prospects for effective treatment of AL amyloidosis?
Systemic amyloidosis is a condition characterized by the extracellular deposition of insoluble fibrillar proteins, leading to organ dysfunction. Its various forms are classified according to the nature of the precursor protein constituent of the fibril for example: immunoglobulin light chains in AL amyloidosis, heavy chains in AH amyloid, serum amyloid A protein, (a component of the acute‐phase response) in AA amyloid, and a heterogeneous group of abnormal proteins in the familial amyloidoses (reviewed in reference 1) (Figure 1). AL amyloidosis is at present considered an incurable disease, with 8 months median survival from the time of diagnosis. The prognosis depends on the dominant organ system affected: patients with cardiac involvement have a median survival of 6 months, compared to 21 months in those with renal disease.

Although there is no treatment which will lead to the resolution of amyloid, regression and clinical improvement have been achieved in those forms of amyloid for which treatment of the underlying disorder is available. This is important, for the presence of amyloid does not preclude supportive and substitution treatment, e.g. dialysis for renal failure. It is now possible to demonstrate this reduction in the amyloid load using 123I‐SAP scintigraphy. This novel technique relies on the fact that all amyloid contains a glycoprotein—amyloid P component—which is in dynamic equilibrium with serum amyloid P (SAP). 123I‐labelled SAP injected intravenously into normal human subjects is catabolized and cleared with a half‐life of 24 h. In patients with amyloid, the labelled SAP is taken up by deposits, and scintigraphic imaging combined with clearance studies gives an indication of the amyloid load and its distribution.2

There is now good evidence of regression of AA amyloidosis in patients with juvenile rheumatoid arthritis treated with chlorambucil. Proteinuria diminishes, the amyloid load detected by 123I‐SAP scintigraphy is reduced, and survival …