A 49-year-old woman was admitted to our hospital for back pain with marked thoracic and extremity deformities leading to bed-rest for three years. She was diagnosed with hypophosphatemic osteomalacia based on her symptoms, X-ray and bone scintigram, high serum alkaline phosphatase level, and low serum levels of both phosphorus and 1,25 dihydroxyvitamin D(3) with inhibition of phosphorus reabsorption. Fanconi syndrome with renal tubular acidosis, vitamin D deficiency and primary biliary cirrhosis were related to the pathogenesis of osteomalacia in this case. Several causal diseases may be concomitantly responsible for acceleration of the severity of osteomalacia in this patient.