ESPE Abstracts

Introduction: Cystinosis is an inherited (autosomal recessive) lysosomal storage disorder characterized by accumulation of cystine crystals in kidney, liver, eyes and brain. Patients can present to pediatric endocrinology clinics with growth retardation and vitamin D resistant rickets particularly in nephropathic infantile form. Here, we aimed to present genetic and clinical spectrum of ten patients who have been followed with the diagnosis of cystinosis, a rare cause of hypophosphatemic rickets, in our clinic.

Material and method: The study included ten patients who have been followed with diagnoses of cystinosis in our outpatient clinic. Data regarding presenting complaint, history, physical examination findings, anthropometric measurements, age, and laboratory findings were extracted from electronic database. Blood samples were drawn into EDTA tubes from all patients and mutation analyses were performed.

Findings: It was found that age range was 2 and 12 years in patients and age at diagnosis was ranging from 6 to 18 months. Overall ten patients (four girls and six boys) from nine families were identified. There was consanguinity between parents in seven families and there was an affected sibling in three families. Proteinuria of varying degrees and hypophosphatemic rickets were present in all patients at presentation. Renal failure of varying degrees developed in four patients during follow-up. In one patient, cystine crystals were detected in eyes at presentation. No cystine crystal was detected in patients underwent bone marrow aspiration. In CTNS gene, c18-21del14bp mutation was detected in four patients, whereas homozygote p.E227E(c.681G>A) mutation was detected in six patients. These mutations were among those recently identified and should considered as explanatory for the disease.

Conclusion: In the present study, we aimed to emphasize that patients presented with hypophosphatemic rickets should be evaluated for proximal tubular dysfunction and cystinosis should be considered in such patients, as consanguinity between parents is relatively high in our province.