ABSTRACT
The Fanconi's syndrome is characterized by generalized disturbance of proximal tubular function. It leads to excessive losses of amino acids, glucose, phosphate, bicarbonate, and other substrates handled by the proximal tubules. The metabolic consequences are acidosis, hypophosphatemia, hypocalcemia, osteomalacia, osteoporosis, and growth retardation. Adult Fanconi's syndrome is mostly secondary form caused by multiple myeloma, primary amyloidosis, light chain nephropathy, and heavy metal poisoning. We experienced 50-year-old woman with kappa light chain disease whose chief complaints were weakness of both lower extremities and multiple bone pain. This patient had renal glycosuria, hypercalciuria, normal anion gap type metabolic acidosis, osteomalacia and normal distal tubule acidification. Her bone marrow biopsy showed inappropriate proliferation of plasma cell. The patient underwent percutaneous renal biopsy in which was exceptionally observed focal effacement of podocyte foot process. So we report a case of osteomalacia caused by adult Fanconi's syndrome and foot process effacement by kappa -light chain disease.