LAUSR

To the Editor: Cystinosis is an autosomal recessive disorder, in which, free cystine accumulates continuously in lysosomes throughout the body [1]. We diagnosed cystinosis when proximal renal tubular acidosis (PRTA), with or without Fanconi syndrome was identified [2]. The same was confirmed when slit-lamp examination revealed corneal cystine crystals. We lacked facilities to study the leukocyte cystine content and pathogenic mutations in the CTNS gene. From 2009 till date, we have identified 8 patients of cystinosis. These were followed till 2021. The age range at presentation was 7 mo to 32 y. The age of patients at presentation was: 7 mo, 8 mo, 15 mo, 18 mo, 36 mo, 12 y, 17 y, and 32 y. There were 3 girls, 4 boys, and 1 adult male. The interval between the first presentation and the diagnosis of cystinosis was 17.7 ± 17.9 mo. The PRTA was diagnosed in 8 (100%) patients, Fanconi syndrome in 5 patients (62.5%), chronic kidney disease (CKD) in 6 (75%) patients, and CKD stage 5D in 5 (62.5%) patients; growth retardation was noticed in all but the adult; infertility was noticed in the adult (12.5%). Slit-lamp examination of eyes revealed corneal crystals in all 8 patients (100%). Renal biopsy revealed cellular variant of focal and segmental glomerulosclerosis in 1 patient while in another it was normal. The mean duration of follow-up was 6.5 ± 2.6 y (range: 1 to 12 y). We treated the patients with the sodium bicarbonate tablets, potassium citrate syrup, calcium and vitamin D supplementation. Chronic kidney disease (CKD) stage 5D evolved in 5 patients. The age of onset of CKD stage 5D was 8.8 y (6–17 y). All but one patient was initiated on peritoneal dialysis. In patients younger than 5 y at the end of the follow-up, the weight and height were < 3rd percentile.