1999 Nature America Inc.• http://genetics. nature. com correspondence nature genetics• volume 23• november 1999 265 sanguineous parents of normal stature. When blood gas analysis revealed pH 7.080 and HCO3–5 mEq/l, the urine pH was 5.5 and HCO3–was 0.3 mEq/l. Urinalysis revealed no glucose, and urinary excretion of amino acids was normal. She is now 11 years old, of short stature (125 cm,–2.4 sd) and has pRTA, bilateral glaucoma, cataracts and bandkeratopathy. Her serum amylase was 242 IU/l. Plasma HCO3–and serum amylase were normal in parents of both patients. cDNA sequencing of the entire kidney SLC4A4 ORF in the patients II. 1 in families A and B revealed a homozygous A→ C transversion at nt 1,043 and a homozygous G→ A transition at nt 1,678, respectively (Fig. 1a, d). Genomic DNA sequencing showed the homozygous mutation in each patient and heterozygosity in their parents, which we confirmed by PCR amplification and digestion of genomic DNA with restriction endonuclease, respectively (Fig. 1b, c, e, f). These two mutations co-