A 14-month-old girl was admitted to our clinic due to failure to thrive. Her weight and height were below the third percentile for age. Laboratory examination showed signs of alkalosis, hypokalemia, and hypochloremia. However, her urinalysis was consistent with renal tubular acidosis. Radiologic examination showed signs of active rickets. Based on clinical and laboratory findings, we focused on the probable diagnosis of cystinosis. Slit-lamp examination of the cornea confirmed our diagnosis. We should note that the presence of alkalosis does not exclude the possibility of diagnosis of cystinosis and we should be aware that if any slight doubt of cystinosis exists, patients should be carefully and completely evaluated for diagnosis.