An Extremely Low-Birth-Weight Infant With Bone Fragility Due to Fanconi Syndrome

Fanconi syndrome is a generalized dysfunction of the renal proximal tubule, leading to growth failure and rickets during childhood. There are few reports of this syndrome in neonates, especially in extremely low-birth-weight infants. We present a case of an extremely low-birth-weight Asian girl with bone fragility because of Fanconi syndrome without underlying diseases. She was born at 29 weeks of gestation and weighed 418 g (-5.2SD). Based on blood and urine analyses, she was diagnosed with Fanconi syndrome. Metabolic acidosis was easily corrected with bicarbonate supplementation. However, the control of the rickets was very difficult, with multiple bone fractures observed despite supplementation of calcium, phosphorus, and vitamin D. Her renal tubular function finally improved at 6 months of age, and oral supplementation of bicarbonate, calcium, and phosphorus was discontinued before discharge. The genetic test for inherited causes of Fanconi syndrome showed no abnormalities. Hypoperfusion during the fetal period was assumed to be one of the causes of Fanconi syndrome in this case.