A Case of Adult Fanconi Syndrome with Hypophosphatemic Osteomalacia / 대한내분비학회지

ABSTRACT

The Fanconi syndrome is characterized by generalized disturbance of tubular function. It leads to excessive losses of amino acids, glucose, phosphate, bicarbonate, and other organic and inorganic substrates handled by the proximal tubules. The metabolic consequences are acidosis, hypophosphatemia, hypocalemia, dehydration, rickets, osteomalacia, osteoporosis, and growth retardation. This syndrome may either be congenital or acquired, primary or secondary. Acquired Fanconi syndrome may result from multiple myeloma, Wilsons disease, primary amyloidosis, light chain nephropathy, and heavy metal poisoning such as lead, mercury, and cadmium. A 33-year-old female presented with multiple bone pain, and progressive proximal muscle weakness for 15 months. The blood urea nitrogen, creatinine, calcium, phosphate, and uric acid were 12.1 mg/dL, 1.5 mg/dL, 8.4 mg/dL, 1.8 mg/dL, and 1.7 mg/dL, respectively. The urine volume, protein, calcium, phosphate, and creatinine clearance were 2,330 ml, 343.7 mg, 146 mg, 424 mg, and 44.6 ml/min, respectively in 24 hour collection urine study. The tubular reabsorption rate of phosphate was decreased. In arterial blood gas analysis study, pH was 7.348, bicarbonate was 17.6 mmol/L, which means metabolic acidosis. In chest X-ray, fracture was seen in eighth and ninth left ribs. The whole body bone scan revealed hot uptake at both first and second ribs, right third rib, both eighth and ninth ribs, left sacroiliac joint and right hip joint. Bone densitometry showed moderate osteopenia in spine and femur neck. After NE4Cl loading, the urine pH was decreased below 5.0 at two and third hour, which means proximal renal tubular acidosis. Amino acid such as, hydroxyproline, threonine, serine, asparagine, glutamine excreted much more than normal in 24 hour urine. Bone biopsy showed the presence of increased osteoid volume and osteoid seam width and marked decreased mineral appositional rate as evidence for osteomalacia. The patients symptoms, including bone pain and proximal muscle weakness, were relieved after supplement of calcitonin, Vitamin D and calcium carbonate. We report a case of Fanconi syndrome with hypophosphatemic osteomalacia with brief review of literature.