Cystinosis: practical tools for diagnosis and treatment

Abstract

Cystinosis is the major cause of inherited Fanconi syndrome, and should be suspected in young children with failure to thrive and signs of renal proximal tubular damage. The diagnosis can be missed in infants, because not all signs of renal Fanconi syndrome are present during the first months of life. In older patients cystinosis can mimic idiopathic nephrotic syndrome due to focal and segmental glomerulosclerosis. Measuring elevated white blood cell cystine content is the corner stone for the diagnosis. The diagnosis is confirmed by molecular analysis of the cystinosin gene. Corneal cystine crystals are invariably present in all patients with cystinosis after the age of 1 year. Treatment with the cystine depleting drug cysteamine should be initiated as soon as possible and continued lifelong to prolong renal function survival and protect extra-renal organs. This educational feature provides practical tools for the diagnosis and treatment of cystinosis.

Clinical utility gene card for: Cystinosis

“…Growth hormone may be indicated in patients with stunted growth despite adequate nutrition and electrolyte balance. [20][21][22] (2) Systemic cysteamine therapy (1.3-1.9 g/m 2 /day) should be administered immediately after making the diagnosis and continued life-long (also after kidney transplantation) to reduce cystine WBC levels to o1 nmol cystine/mg protein. 20,22 (3) Topical cysteamine eye drops (0.5%) should be administered at least 4 times daily to reduce corneal cystine crystals.…”

“…[20][21][22] (2) Systemic cysteamine therapy (1.3-1.9 g/m 2 /day) should be administered immediately after making the diagnosis and continued life-long (also after kidney transplantation) to reduce cystine WBC levels to o1 nmol cystine/mg protein. 20,22 (3) Topical cysteamine eye drops (0.5%) should be administered at least 4 times daily to reduce corneal cystine crystals. 16 (4) Renal transplantation 3.2 Predictive Setting: The tested person is clinically unaffected but carries an increased risk based on family history (To be answered if in 1.9 'B' was marked)…”

Infantile Nephropathic Cystinosis: A Novel CTNS Mutation

“…There are three different clinical forms of cystinosis according to disease severity, which depend on the age at presentation and the degree of accumulation of cystine: the infantile nephropathic form, which is the most common and most severe form of cystinosis; the late-onset adolescent form (intermediate form or juvenile nephropathic form); and the benign adult form (non-nephropathic form or ocular non-nephropathic form) [2]. The function of proximal tubular transporters is progressively lost in INC because of the accumulation of cystine, which results in Fanconi' s syndrome.…”

“…The CTNS gene, which consists of 12 exons, is located on chromosome 17p13.3. Over 100 mutations have been reported [2]. Here, we report two patients with INC together with their molecular genetic analysis and describe a new mutation on the CTNS gene.…”

“…This metabolic disorder causes abnormal accumulation of cystine in lysosomes [1]. Infantile nephropathic cystinosis (INC) is one of the major complications of the disease and is characterized by failure to thrive and clinical symptoms related to Fanconi's syndrome during the first year of life [2]. The CTNS gene, which consists of 12 exons, is located on chromosome 17p13.3.…”