The history of cystinosis is one of the most successful examples of rare disease research leading to meaningful treatments. In a recent interview with the European Medical Journal, William Gahl—a physician-scientist who helped uncover the cause of cystinosis and develop its first targeted therapy—reflects on how understanding of the disease has changed over the past 50 years and what future advances may mean for families.

Early Days: When Little Was Known

When the researcher first encountered children with cystinosis during his pediatric training, there was no treatment to address the underlying disease process. Doctors knew that cystinosis caused severe kidney problems in infancy and childhood, but they did not understand exactly why.

At that time, children with the most severe form of cystinosis typically developed Fanconi syndrome, a condition in which the kidneys lose important nutrients and minerals into the urine, during their first year of life. Many reached kidney failure by age 9 or 10.

As kidney transplantation became available in the late 1960s, patients began surviving into adulthood. This revealed something important: cystinosis was not just a kidney disease. Doctors began to recognize problems affecting the eyes, muscles, hormones, nervous system, and other organs.

Discovering the Cause of Cystinosis

One of the most important breakthroughs came when researchers determined what was happening inside cells.

Cells contain structures called lysosomes, which act like recycling centers. They break down proteins and other materials into smaller building blocks that can be reused. In people with cystinosis, the amino acid cystine accumulates abnormally inside lysosomes.

For many years, scientists assumed that cystinosis must be caused by a missing enzyme because most known lysosomal diseases were enzyme disorders. However, experiments failed to support that theory.

Eventually, researchers discovered that the real problem was different: cystine could not leave the lysosome because the transport system responsible for moving it out was defective. The protein that normally performs this task is called cystinosin.

This finding changed not only the understanding of cystinosis but also the wider field of rare diseases. It showed that some diseases are caused not by faulty enzymes, but by faulty cellular transport systems.

Understanding Why the Disease Affects So Many Organs

As research progressed, doctors learned that cystinosis exists on a spectrum.

Some individuals have the classic infantile form, which is the most severe, while others have milder forms that develop later in childhood or adulthood. Researchers discovered that these differences are related to how much function remains in the cystinosin protein.

Scientists also learned why cystinosis causes such a broad range of symptoms. The buildup of cystine damages many tissues throughout the body. The kidneys are affected particularly early because they constantly process and recycle proteins, generating large amounts of cystine.

This growing understanding allowed doctors to identify patients earlier and tailor treatment more effectively.

The Development of Cysteamine: A Landmark Achievement

Perhaps the most important advance in cystinosis care was the development of cysteamine, the first medication designed to address the underlying disease.

Researchers discovered that cysteamine works around the defective transport system. Inside the lysosome, it reacts with accumulated cystine and converts it into compounds that can leave the lysosome through alternative pathways.

This elegant solution arose directly from understanding the disease mechanism at the cellular level.

However, turning that discovery into an approved treatment took many years.

Because cystinosis is rare, finding enough patients for clinical trials was difficult. Researchers also had to determine how best to measure treatment success. Kidney damage develops slowly, making it challenging to demonstrate benefits during a study period.

The interviewee notes that some early studies included patients who already had advanced kidney failure. Those studies failed to show benefit, temporarily discouraging some physicians from using cysteamine. Eventually, larger and longer studies demonstrated that the drug could preserve kidney function when started earlier.

International clinical trials began in 1978, and an oral cysteamine treatment received U.S. Food and Drug Administration approval in 1994.

Later improvements included:

• Delayed-release cysteamine capsules that can be taken every 12 hours instead of every 6 hours.
• Cysteamine eye drops, which dissolve cystine crystals in the cornea, the transparent front surface of the eye.

Together, these therapies transformed cystinosis from a disease associated with early death into a chronic condition that can be managed throughout life.

The Importance of Lifelong Care

Although treatment has dramatically improved outcomes, cystinosis remains a complex, lifelong condition.

Today’s patients require care from many specialists, including kidney doctors, eye doctors, neurologists, endocrinologists (hormone specialists), transplant teams, physical therapists, social workers, and counselors.

The interview emphasizes that cystinosis has become a “team enterprise,” requiring coordinated care across multiple medical disciplines.

Families continue to face challenges, including:

• Managing treatment schedules.
• Transitioning from pediatric to adult medical care.
• Accessing centers with expertise in cystinosis.
• Coping with cysteamine’s unpleasant taste and smell, which can make long-term adherence difficult.

Why Newborn Screening Could Be Revolutionary

One of the most promising developments discussed in the interview is newborn screening.

Currently, children are often diagnosed around 14 months of age, after kidney damage has already begun. Research suggests that identifying affected babies shortly after birth and starting cysteamine within the first weeks of life may prevent much of this early injury.

The interviewee describes newborn screening as potentially “of huge importance for the community.” Early studies have demonstrated that very early treatment can protect both the kidney tubules and the filtering units of the kidneys.

For families, this could mean healthier childhoods and better long-term outcomes.

Looking Toward Gene Therapy

Researchers are also exploring ways to go beyond cysteamine.

Gene therapy aims to correct or replace the faulty gene responsible for cystinosis. Rather than treating the consequences of the disease, gene therapy could potentially address the root cause.

The interview highlights gene therapy directed at organs most affected by cystinosis, particularly the kidneys and muscles, as one of the most promising future approaches.

Other experimental strategies include gene editing and specialized genetic medicines designed to target specific DNA changes.

Lessons for the Entire Rare Disease Community

The cystinosis story offers important lessons that extend far beyond a single disease.

The researcher stresses that progress depended on several factors working together:

• Fundamental laboratory research to understand the disease mechanism.
• Accurate diagnostic tests.
• Long-term clinical trials.
• Government funding and support.
• Pharmaceutical industry involvement.
• Active engagement by patient advocacy organizations.
• Information sharing among researchers worldwide.

Patient organizations played a particularly important role by supporting research, raising awareness, and helping connect families and scientists.

A Message of Hope

Perhaps the strongest theme throughout the interview is that scientific understanding can change lives.

Fifty years ago, cystinosis was largely viewed as a devastating childhood kidney disease with few treatment options. Today, physicians understand its genetic cause, can measure disease activity, have treatments that slow its progression, and are exploring newborn screening and gene-based therapies that may further improve outcomes.

As the interviewee advises future researchers, it is important to “keep their eye on the prize: treatment.”

For families living with cystinosis, the history of the disease provides a powerful reminder that research matters. Every major improvement in care, from identifying the defective cellular transport system to developing cysteamine and exploring gene therapy, began with scientists asking fundamental questions about how the disease works. Those discoveries have already transformed countless lives and continue to create hope for the future.