Cystinosis
Cystinosis
Also known as:CTNS-related cystinosis, nephropathic cystinosis, ocular cystinosis, China Second Rare Disease Catalog item 21
Cystinosis is an inherited CTNS-related lysosomal storage disorder in which cystine builds up inside cells, mainly damaging the kidneys and eyes but also affecting the thyroid, muscles, pancreas, and reproductive system.
Start Here
A quick guide to the next step: which department to start with, what to prepare, and what to ask.
Infants with excessive thirst and urination, dehydration, poor growth, rickets, or electrolyte problems should see pediatric nephrology or metabolic genetics; light sensitivity or corneal crystals should involve ophthalmology.
CTNS affects the lysosomal transporter that moves cystine out of cells. When cystine accumulates, it forms crystals and damages organs, with infant kidney Fanconi syndrome and corneal crystals being key early clues.
Care focuses on early cysteamine therapy, replacing kidney tubular losses, protecting kidney function, and treating corneal crystals with eye medicine. Advanced kidney failure may require dialysis or transplant.
Cystinosis is autosomal recessive. Parents are usually healthy carriers. Genetic counseling after diagnosis helps with parental confirmation, sibling screening, and future pregnancy planning.
Early symptoms may be labeled feeding problems, rickets, dehydration, renal tubular acidosis, or poor growth. The combination of Fanconi syndrome and eye findings should prompt testing.
This page helps patients and families organize care leads. It does not replace a clinician’s diagnosis or treatment plan. For testing, medication, referrals, emergency care, and support applications, follow qualified clinicians, medical institutions, support organizations, and official sources.
Diagnosis Path
Organized around the practical patient journey: identify clues, avoid common delays, then prepare for care.
When to Suspect It
- An infant has excessive urination and thirst, repeated dehydration, vomiting, constipation, poor appetite, or poor height and weight gain.
- Tests suggest Fanconi syndrome: urine glucose with normal blood glucose, low phosphate, low potassium, metabolic acidosis, proteinuria, or aminoaciduria.
- There is rickets, bowed legs, bone pain, weakness, eye light sensitivity, tearing, or squinting.
- An adolescent or adult has unexplained tubular kidney problems, corneal crystals, or family history.
Common Wrong Turns
- Treating rickets only as nutrition or vitamin D deficiency without checking urine glucose, electrolytes, and kidney tubules.
- Replacing fluids and electrolytes without looking for the metabolic cause of Fanconi syndrome.
- Treating light sensitivity as conjunctivitis or dry eye without slit-lamp examination.
- After diagnosis, not monitoring leukocyte cystine level, extra-kidney organs, and adherence.
Departments to Start With
- Pediatric nephrology
- Metabolic genetics
- Pediatric ophthalmology
- Nephrology
Before the Visit
- Track thirst, urination, dehydration, vomiting, constipation, feeding, growth curves, and bone problems.
- Bring urinalysis, urine glucose, urine protein, electrolytes, blood gas, kidney function, phosphate, calcium, alkaline phosphatase, and bone imaging.
- Bring slit-lamp examination results, corneal crystal documentation, and prior genetic reports.
- Summarize family history of kidney failure, poor childhood growth, recurrent dehydration, or eye problems.
Tests to Ask About
- Leukocyte cystine level for diagnosis and treatment monitoring.
- CTNS genetic testing with parental and sibling confirmation when appropriate.
- Fanconi syndrome evaluation: urine glucose, aminoaciduria, phosphate, potassium, bicarbonate, urine protein, and kidney function.
- Slit-lamp examination and follow-up of thyroid, pancreas, muscles, swallowing, and reproductive issues.
Questions for the Doctor
- Is this nephropathic, intermediate, or ocular cystinosis, and what is the kidney stage?
- What is the cysteamine treatment target, and how often should leukocyte cystine be checked?
- Which electrolytes, alkali, phosphate, vitamin D, or nutrition support are needed?
- How should eye treatment, extra-kidney monitoring, and transplant planning be scheduled?
- Should family members be tested, and what reproductive counseling is available?
Basic Information
Medical Notes
More complete medical explanations are kept here for discussion with clinicians.
Symptoms
Nephropathic cystinosis usually appears in infancy with renal Fanconi syndrome, causing excessive urination and thirst, repeated dehydration, vomiting, poor growth, electrolyte problems, metabolic acidosis, and hypophosphatemic rickets. Without sufficient treatment, chronic kidney disease or kidney failure can develop.
Cystine crystals in the cornea can cause light sensitivity, eye pain, tearing, and visual discomfort. Later-onset kidney disease or ocular-only disease can occur. Some people also develop thyroid, pancreas, muscle, swallowing, or male fertility problems.
Diagnosis
Diagnosis combines Fanconi syndrome, corneal crystals, leukocyte cystine levels, and CTNS genetic testing. Slit-lamp examination can show corneal cystine crystals, though they may not be obvious in very young infants.
Clinicians also rule out other causes of Fanconi syndrome or renal tubular acidosis, such as hereditary fructose intolerance, galactosemia, Wilson disease, mitochondrial disease, and drug or toxin-related tubular injury.
Treatment
Systemic cysteamine lowers intracellular cystine and is central to slowing kidney and extra-kidney damage. Corneal crystals usually require cysteamine eye treatment because systemic therapy has limited corneal effect.
Care also includes fluids, alkali, potassium, phosphate, vitamin D, nutrition support, and rickets management. Dialysis or kidney transplant may be needed for end-stage kidney disease, but extra-kidney cystine issues still require monitoring after transplant.
Long-term Care
Follow-up includes leukocyte cystine levels, kidney function, urine protein, electrolytes, bones, growth, ophthalmology, thyroid, blood glucose, muscles, and swallowing function. Because medication schedules can be complex, adherence support matters.
Patients should keep genetic reports, cystine levels, kidney function trends, and transplant records for care across centers.
Fertility and Family
Cystinosis is autosomal recessive. Parents are often carriers, and pregnancy risk depends on both parental variants. Siblings may need screening.
Families planning pregnancy can discuss carrier testing, prenatal diagnosis, or preimplantation genetic testing.
When to Seek Urgent Care
Seek emergency care for marked dehydration, sleepiness, persistent vomiting, seizures, deep rapid breathing, severe weakness, abnormal heartbeat, low urine output, or infection with worsening kidney function. Bring the diagnosis and current fluid, electrolyte, and cysteamine plan.
Prognosis
Early diagnosis and sustained cysteamine plus kidney tubular support can delay kidney failure and extra-kidney complications; delayed treatment or poor adherence increases risk.