BACKGROUND AND OBJECTIVES: Infantile nephropathic cystinosis is a severe disease 
that occurs due to mutations in the cystinosis gene, and it is characterized by 
progressive dysfunction of multiple organs; >100 cystinosis gene mutations have 
been identified in multiple populations. Our study aimed to identify the 
clinical characteristics and spectrum of cystinosis gene mutations in Turkish 
pediatric patients with cystinosis.
DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We identified the clinical 
characteristics and spectrum of cystinosis gene mutations in Turkish patients 
with cystinosis in a multicenter registry that was established for data 
collection. The data were extracted from this registry and analyzed.
RESULTS: In total, 136 patients (75 men and 61 women) were enrolled in the 
study. The most common clinical findings were growth retardation, polyuria, and 
loss of appetite. None of the patients had the 57-kb deletion, but seven novel 
mutations were identified. The most common mutations identified were c.681G>A 
(p.Glu227Glu; 31%), c.1015G>A (p.Gly339Arg; 22%), and c.18_21 del 
(p.Thr7Phefs*7; 14%). These mutations were associated with earlier age of 
disease onset than the other mutations. To understand the effects of these 
allelic variants on clinical progression, the mutations were categorized into 
two major groups (missense versus deletion/duplication/splice site). Although 
patients with missense mutations had a better eGFR at the last follow-up visit, 
the difference was not significant. Patients in whom treatment began at age <2 
years old had later onset of ESRD (P=0.02). Time to ESRD did not differ between 
the patients with group 1 and group 2 mutations.
CONCLUSIONS: The most common cystinosis gene mutations identified in Turkey were 
c.681G>A (p.Glu227Glu), c.1015G>A (p.Gly339Arg), and c.18_21 del 
(p.Thr7Phefs*7). Patients with less severe cystinosis gene mutations tend to 
have better kidney outcome.