Evaluation of genotype, phenotype, treatment and long-term prognosis of patients with cystinosis followed in Çukurova University Medical Faculty Balcali Hospital

Aim:The aim was to examine the demographic, genetic characteristics, systemic involvements at firstand last admission, treatment responses and renal involvement of patients followed-up with cystinosis. The relationship between clinical findings and age at diagnosis, cystine levels at diagnosis and follow-up were evaluated. The patients were assessed in terms of genotype-phenotype relationship, bone health and neurological involvement. Material and Method: Patients followed-up between 2000-2021 were evaluated retrospectively. Age at first admission-diagnosis, parental consanguinity, positive family history, complaints at admission, anthropometric data at first-last admission, kidney functions, systemic findings, leukocyte cystine levels, cerebral imaging, electromyography, bone mineral densities, hearing, intelligence and development tests, gonad and thyroid hormone results were recorded. Results: Of 51 patients, 51% were female, 49% male. 88.2%had infantile, 11.8% juvenilecystinosis. Parental consanguinity was 84.3% and positive family history was 39.2%. A significant decrease was observed in the glomerular filtration rates at the last admission in juvenile type patients (p=0.028). A positive correlation was observed between the age at which chronic kidney disease developed and the age at diagnosis (r=0.512; p=0.008). The leukocyte cystine levels were higher in those with endocrine system involvement at first admission. Six patients had osteopenia, 4 patients had osteoporosis, three patients had neuropathy, and 1 had myopathy. 8 patients had personal-social, fine motor, gross motor and language developmental delay detected by DENVER-II test. Varying degrees of mental retardation was present in 12 patients. The most common pathogenic variants in CTNS gene were c.451A>G(41.2%), c.681G>A(39.2%), c.834_842del(15.7%). Patients with c.451A>G variant had delay at the age at diagnosis and development of chronic kidney disease. Statistically significant differences were found between laboratory, clinical and kidney functions of eight sibling couples. Conclusion:With our study, 1 new pathogenic variant was added to the literature. The c.451A>G variant associated with infantile cystinosis was seen in 6 patients with the juvenile type. The highest number of patients with mental involvement was reported. The differences in siblings with the highest number were noted.Our thesis study has been one of the most comprehensive studies done in our country. Keywords: Cystinosis, Cystine, CTNS, Chronic Kidney Failure, Kidney Transplant