Genetic and long-term data on a patient with permanent isolated proximal renal tubular acidosis

A 12-year-old girl presented with permanent isolated proximal renal tubular acidosis (pRTA), glaucoma, band keratopathy, mild cataract and short stature. Severe metabolic acidosis was caused by the impairment of bicarbonate reabsorption in the proximal tubules and alkali therapy improved her acidaemia. A homozygous G to A transition at nucleotide 1,678 in the basolateral kidney type Na⁺/HCO₃ ⁻ (kNBC) co-transporter gene SLC4A4, which is critical in HCO₃ ⁻ resorption in renal proximal tubules, was identified. Her height and height velocity (HV) were very low (−4.0 SD and −4.4 SD, respectively) before alkali treatment, but both improved after initiating alkali therapy at the age of 2 years and 3 months. The patient's body height and HV were 131.5 cm (−2.7 SD) and 4.0 cm (−2.0 SD), respectively at the age of 12 years. Conclusion This case demonstrates that early administration of alkali therapy and sustained correction of acidosis, even if inadequate to correct the metabolic acidosis, can markedly improves growth in permanent isolated proximal renal tubular acidosis. Received: 3 April 2000 / Accepted: 5 July 2000