About nephropathic cystinosis
What is nephropathic cystinosis?
Nephropathic cystinosis is the most common form of cystinosis, a rare, inherited condition that affects every cell of the body by causing buildup of the amino acid cystine. The buildup of cystine causes kidney and other problems throughout the body. These problems cause the body to lose too much sugar (glucose), proteins, and salts (electrolytes) through the urine. Nephropathic cystinosis may lead to slow body growth and small stature, weak bones, hypothyroidism, blindness, muscle weakness, pulmonary dysfunction, and developing and worsening kidney failure.1-5
It is estimated that there are currently about 500 people in the United States—and 2,000 worldwide—diagnosed with this disorder.6 Nephropathic cystinosis is classically associated with blond-haired, blue-eyed children of European descent, although all races and ethnic backgrounds may be affected.3 The disease tends to affect more males than females, 1:4:1 according to one study.4
How nephropathic cystinosis affects the body
Although nephropathic cystinosis affects the entire body, the kidneys and eyes are typically affected first.3 Nephropathic cystinosis is the leading cause of Fanconi syndrome, a disorder of the kidney tubules in which important nutrients and minerals are released into the urine and must be replaced.3,7 Before the availability of cystine-depleting medication, nephropathic cystinosis would progress to kidney failure, usually between 9 and 10 years of age.5,7 Today, cystine-depleting medication may delay the progression of cystinosis and certain complications of the disease.4
In the eyes, cystine crystals form on the cornea. This can cause people with cystinosis to experience severe light sensitivity, which means that a bright sunny day can be painful; they may want to avoid bright lights or wear sunglasses to be more comfortable. Sometimes they may need to wear sunglasses indoors.3,8 Cystine-depleting eyedrops are used to dissolve corneal crystals.3 In addition to forming in the kidneys and eyes, cystine crystals can also form in such organs and tissue as the liver, spleen, lymph nodes, thyroid, intestines, muscle, brain, and bone marrow.3
Over time, nephropathic cystinosis can lead to damage to the heart, central nervous system, and muscle tissue.3 Ongoing, regular treatment is needed to continuously lower cystine concentration in the cells, which may delay or prevent irreversible organ damage.7 To determine how effectively treatment is working, people with nephropathic cystinosis should monitor their cystine concentration via frequent white blood cell cystine testing.11