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AL amyloidosis is a rare disorder characterised by tissue deposition of a fibrillary proteinaceous material, formed from monoclonal immunoglobulin light (or exceptionally heavy) chains. Although it may complicate multiple myeloma or B-cell lymphomas, AL amyloidosis is often associated with a low burden of clonal plasma cells ("primitive" AL amyloidosis). The mechanisms involved in the formation of AL amyloid deposits remain unclear, but are probably related to structural peculiarities of monoclonal immunoglobulin light chains. AL amyloidosis is usually a systemic disease, often revealed by renal involvement, the most common complication of the disease. The longterm prognosis of AL amyloidosis is poor, mainly related to amyloid restrictive cardiomyopathy leading to congestive heart failure. Oral melphalan and prednisone is considered the standard treatment for AL amyloidosis, but with limited increase in the median survival. High-dose intra-venous melphalan with autologous stem cell transplantation is an effective treatment, aimed at eliminating the clonaly expanded plasma cells, which has been shown to induce complete hematologic remissions and to prolong survival. However, the tolerability of such treatment is low, limiting its use to selected patients. The development of new drugs, able to interfere with amyloid fibril deposition, may provide a new therapeutic approach.

A frequent complication of hemodialysis is deposition of beta 2-microglobulin amyloid in tendons and joints. Soft tissues involvement is exceptional. A 74 year-old woman on hemodialysis for 21 years developed two bilateral and symmetric tumours in gluteal regions causing discomfort when sitting. Histology, immunohistochemistry and electron microscopy showed that deposit consisted of predominant beta 2-microglobulin and lambda light chain. This is an unusual localisation of amyloidosis developing late in the course of hemodialysis. It may be perhaps initiated by chronic traumatism and be promoted by the light chain lambda of immunoglobulin.

Intravesical Bacillus Calmette-Guerin has proved to be the most effective treatment of superficial bladder carcinoma. This therapy may induce a renal failure of variable severity, sometimes associated with multiple organ failure. Renal prognosis of this complication is not well defined. We report on a 68 year-old male patient who developed granulomatous hepatitis and acute tubulo-interstitial nephritis with mononuclear infiltrates containing numerous epithelioid cells, following the third course of intravesical BCG. Eleven cases of renal impairment due to intravesical BCG have been previously described, as part of a systemic disease in seven patients. The potential pathophysiological mechanisms of this rare complication are precised.