Case Studies

 Case 9.9 Idiopathic amyloid

A 52-year-old woman presented with increasing swelling of both legs over a period of 3 months. Fourteen years earlier she had been treated for tuberculosis. On examination, she was pale, with gross bilateral leg oedema extending to the umbilicus and a large infected ulcer on the medial aspect of the right leg. Chest X-ray and electrocardiogram were normal but she had a microcytic anaemia (Hb 75g/l) with an erythrocyte sedimentation rate (ESR) of 140mm/h. Her initial biochemical results showed a low serum albumin (14g/l) and marked proteinuria (12g/day) but a normal blood urea, serum creatinine and creatinine clearance. Serum electrophoresis showed no monoclonal band. Serum immunoglobulin levels were: IgG 2.2g/l (NR 7.2-19.0); IgA 1.2g/l (NR 0.8-5.0); and IgM 1.2g/l (NR 0.5-2.0). Electrophoresis of a concentrated (x20) urine sample showed considerable amounts of albumin and gammaglobulin and an M band in the beta region. Immunofixation of the serum and urine showed the presence of monoclonal free lambda light chains in the urine only.

The presence of urinary monoclonal light chains suggested a possible diagnosis of light-chain myeloma or renal amyloid. A rectal biopsy was performed to look for amyloid deposits: this showed deposition of small amounts of amorphous material around blood vessels. This material stained strongly with Congo red and showed green birefringence when viewed under polarized light, an appearance which is characteristic of amyloid. A renal biopsy was also performed: striking deposits of amyloid were found in the GBM, in the tubular basement membrane and in the walls of several arteries.

In view of her past medical history, the amyloid could have been associated with the previous tuberculosis or with the chronic infection of her leg ulcer; this is acute-phase-associated amyloid (see Table 9.5). However, antisera to lambda light chains stained the material in both biopsies, showing that the amyloid was light-chain-associated (Table 9.5) and thus idiopathic or due to multiple myeloma. The absence of suppression of IgA and IgM levels, the lack of infiltration of the bone marrow and the absence of osteolytic lesions on X-ray excluded the diagnosis of multiple myeloma. Therefore, this was idiopathic amyloid. In view of her reasonable renal function, only supportive treatment was given; this consisted of a low-salt, high-protein diet and diuretics. To date, her proteinuria has persisted but has not worsened.