cystinosis

Cystinosis is a rare metabolic disease caused by an abnormal buildup of cystine inside cell compartments called lysosomes. This buildup can damage various organs, most the kidneys and eyes. Mutations in the CTNS gene affect the normal movement of cystine in and out of cells, leading to problems that may be seen in different forms, including infantile nephropathic, juvenile nephropathic, and ocular types. It is estimated to affect about 1 to 9 in 100,000 people. The severity and specific features can vary considerably from person to person.

The clinical presentation of cystinosis reflects its multisystem nature. Renal involvement is prominent, with nearly all affected individuals experiencing signs of renal Fanconi syndrome, hypophosphatemia, hypokalemia, aminoaciduria, proteinuria, and overall renal tubular dysfunction, which contribute to chronic kidney problems. Ocular symptoms, such as corneal opacity and photophobia, frequently occur along with other features like fatigue, vomiting, dehydration, and polydipsia. Endocrine and musculoskeletal issues, including short stature, delayed puberty, myopathy, muscle weakness, and metabolic complications such as type I diabetes mellitus and hypothyroidism, are also reported. Not all individuals experience all of these features, and severity varies considerably.

Cystinosis arises from pathogenic variants in the CTNS gene, which encodes a protein essential for transporting cystine out of lysosomes. When the CTNS protein does not function properly, cystine accumulates within the lysosomes, leading to cellular damage and dysfunction in organs such as the kidneys and eyes. Specific details regarding the inheritance pattern are not provided; however, genetic counseling can help families understand potential risks and consider options for family planning.

Currently, management focuses on supportive care and symptom relief, as there are no FDA-approved treatments specifically for cystinosis. Treatment is tailored to the individual and typically involves a multidisciplinary approach with regular monitoring and surveillance to track kidney function, ocular health, and other systemic complications. Patients benefit from coordinated care involving specialists who can address the renal, ocular, endocrine, and musculoskeletal aspects of the disease. Genetic counseling is also recommended to inform families about the condition and discuss potential future options.

Outcomes in cystinosis vary depending on the severity of symptoms, the age at diagnosis, and access to comprehensive care. With current standards of care and supportive management, many individuals experience improvements in quality of life despite early challenges with kidney function and growth. The clinical course is highly variable and may include periods of stabilization following early complications. Outcomes described in medical literature continue to evolve as standards of care improve. Families often find it helpful to connect with specialists familiar with this condition for ongoing guidance and support.

Cystinosis is an active area of research with several clinical trials currently investigating novel treatment approaches. Active research efforts are exploring ways to improve cystine clearance and mitigate organ damage, and individuals interested in clinical trials can search ClinicalTrials.gov or consult their care team about eligibility.