We report a patient with renal tubulointerstitial
fibrosis and symptomatic
osteomalacia associated with
Fanconi syndrome. A 55-year-old woman was hospitalized because of an inability to walk. Beginning approximately 2 years previously, she had experienced gradually worsening
pain in the hips, shoulders, and trunk, culminating in a bedridden state. Serum
urea nitrogen was 38 mg/dl;
creatinine, 2.6 mg/dl;
uric acid. 3.6 mg/dl;
phosphate, 2.3 mg/dl; and
alkaline phosphatase, 2111 IU/l. Urinary beta2 microglobulin was 72 331 microg/day.
Aminoaciduria, renal glucosuria, and
proximal renal tubular acidosis with a normal anion gap were also noted. The patient was diagnosed with
Fanconi syndrome. Radiography demonstrated typical Looser zones in the proximal portion of the left and especially the right femoral shaft, and at several other sites. A renal biopsy specimen disclosed severe tubulointerstitial
fibrosis with little cellular infiltration. Glomeruli were largely intact. A bone biopsy specimen indicated
osteomalacia; no
tetracycline labeling could be seen along most trabecular bone surfaces, and the ratio of total osteoid volume to bone volume was increased (71.8%).
Bicarbonate administration (9 g/day) gradually lessened most symptoms, permitting ambulation.
Calcitriol administration decreased excessive intact-
parathyroid hormone emerging after 2 months of
acidosis correction. Thus, severe
acidosis associated with
Fanconi syndrome can induce
osteomalacia showing serious skeletal complications, but also responsiveness to
bicarbonate therapy.