Diagnosis and Symptoms

Cystinosis diagnosis

Cystinosis symptoms typically appear within the first year of life. While children born with cystinosis tend to have normal length and weight at birth, their growth falls notably short during the first year of life.1

If a doctor suspects that a child might have cystinosis, he or she may:2

  • Check the child’s eyes for crystals in the cornea.
  • Order a special blood test called a white blood cell (WBC) cystine test.

This test measures how much cystine has built up in the blood cells. A child with cystinosis can have up to 100 times the normal level.

Cystinosis in the body

Cystinosis can affect every part of the body. Cystine, which forms as crystals in many tissues, can severely damage the kidneys. Both through kidney impairment and Fanconi syndrome, critical elements like water, electrolytes, proteins, potassium, and sugars are lost. Uncontrolled, this impairment can lead to kidney failure.1,2

Over time, toxic levels of cystine accumulation can result in damage to multiple organs and tissues throughout the body, including the:1

  • Kidney
  • Brain
  • Eyes
  • Liver
  • Thyroid
  • Intestines
  • Lymph nodes
  • Muscles
  • Spleen
  • Bones and bone marrow

Common signs & symptoms

Symptoms start to develop between 6 and 12 months of age, and may progress at a different rate for each person. The following are some common symptoms of cystinosis.1

Infancy

Failure to thrive/slowed growth

Children with cystinosis may have normal weight and height at birth, but their growth does not keep up with expectations. This is called “failure to thrive” or “slowed growth” and can be an early indicator of cystinosis, usually becoming evident at 6 to 12 months of age.1

  • Feeding difficulties such as feeling full from consuming large amounts of fluids, lack of appetite (anorexia), vomiting, lacking saliva, and a distorted sense of taste, combined with losses of nutrients in the kidneys, can result in poor nutrition and contribute to slowed growth.1,2 See the Nutrition page to learn more.
  • Underperformance of the thyroid, called hypothyroidism, can also contribute to slowed growth.3
  • Poor growth is also partially due to metabolic acidosis, or the buildup of acid in the body.2

Fanconi syndrome

Cystinosis is the most common cause of Fanconi syndrome, a disorder of the kidney tubules that typically appears in cystinosis patients at around 6 months of age.1 Fanconi syndrome occurs when the renal tubules—tiny canals in the kidneys responsible for reabsorption, secretion, and collection of various substances—cease to function properly. Fanconi syndrome causes loss of many key substances necessary for normal health, including glucose, phosphate, amino acids, calcium, magnesium, sodium, and potassium.2 Urination increases dramatically in Fanconi syndrome, resulting in dangerous dehydration, which worsens kidney impairment and requires immediate medical attention.1

Rickets

In people with cystinosis, important minerals can be lost because of frequent urination. One important nutrient that can be lost is phosphorous. A person who loses too much phosphorous can develop rickets, a softening or weakening of bones.1,4 Although a deficiency of vitamin D is typically the cause of rickets, when rickets occurs in people with cystinosis, it is generally hypophosphatemic rickets, rickets caused by too little phosphorus.2,4 In addition to bone softening, rickets can cause bone deformities and bone fragility, and delay walking in young children.1

Childhood

Photophobia

Sensitivity to light, or photophobia, is a common symptom of uncontrolled cystinosis. With severe photophobia, light isn’t just bright; it’s painful.5 Photophobia arises when cystine crystals accumulate in the cornea during the first 10 years of life.2 Later in life, uncontrolled cystine accumulation could result in retinal blindness.1,2 Avoidance of very bright lights, especially the sun, as well as wearing dark sunglasses can help lessen eye-related symptoms.2,5,6 Cystine-depleting eyedrops can dissolve cystine crystals in the eyes and help to prevent or delay eye-related or ocular complications.1

Hypothyroidism

Hypothyroidism is a condition in which the thyroid gland, located in the front of the neck, does not produce enough thyroid hormones. Hypothyroidism is common in individuals with cystinosis.7 It typically develops by age 10.1
Thyroid hormones control overall metabolism and many other bodily functions, so it’s very important to both growing children and adults. Symptoms are far ranging and can include slowed growth rate; poor muscle tone; puffy face, hands, and feet; dry skin and scalp; and sluggishness and fatigue.3

Hypothyroidism may be controlled with levothyroxine therapy.1

Chronic renal failure/kidney impairment

The rate at which cystinosis affects the kidneys is different in each person with cystinosis. Some people experience a rapid decline in kidney function. In others, the decline might happen slowly or appear to stop for a time.2 When cystine accumulation is not controlled, patients can develop kidney failure, also called end-stage renal disease (ESRD), at around 10 years of age.7 Dialysis or kidney transplant are then needed.1 Cysteamine (cystine-depleting therapy) can delay kidney failure and the need for transplant from about age 10 to about age 20.7

Intense thirst is a common sign associated with cystinosis. This is due to impaired kidney function, which results in the need to urinate frequently. This isn’t just inconvenient. It’s dangerous because the body loses a lot of water, salt, and electrolytes, and there is the potential for reduced volume of blood circulating in the body.2 People with the condition need to drink a lot of fluids and electrolytes to make up for the losses due to dehydration. Vitamin D and phosphates may be administered to make up for the loss of these compounds and to avoid rickets.2

Adulthood

Thanks to treatment innovations, as well as earlier diagnosis, people with cystinosis are living longer than ever before. Later in life, even after a renal transplant, complications of cystinosis may develop owing to longstanding accumulation of cystine crystals.8

Retinal blindness

The retina is a layer of tissue at the back of the eye that senses light and sends images to the brain.9 In people with uncontrolled cystinosis, this sensitive tissue can become damaged and blindness can develop.1 Long-term and regular use of cysteamine (cystine-depleting therapy) can prevent severe damage to the eyes.7

Myopathy, including difficulty swallowing and pulmonary dysfunction

Myopathy is a disease of the muscles. If cystinosis is inadequately treated, a progressive pattern of limb-muscle weakness and wasting can occur. This muscle wasting begins in the hands and can ultimately affect the mouth, throat, and chest. As muscle wasting becomes more severe, weakness in the hands can begin to affect dexterity, making everyday tasks more difficult. Weakness of muscles in the chest can reduce respiration and proper breathing, while muscle wasting around the mouth and throat can result in problems with feeding and swallowing, airway obstruction, and distortion of speech. Long-term use of cysteamine (cystine-depleting therapy) may help prevent myopathy.10

Diabetes mellitus

If cystine builds up in the pancreas, the damage can result in diabetes mellitus.7 In a person with diabetes mellitus (also called Type 2 diabetes), the pancreas doesn’t produce enough insulin, which is important to convert sugar from the foods you eat into energy your cells can use.11 Long-term use of cysteamine (cystine-depleting therapy) can prevent diabetes mellitus.7 If diabetes develops, it requires regular and vigilant treatment with insulin.7 Complications of uncontrolled diabetes are very serious.11

Stomach/gastrointestinal issues

Uncontrolled cystinosis frequently brings gastrointestinal (GI) problems, particularly nausea, vomiting, and dysfunction of the nerves or muscles in the intestinal tract, known as dysmotility.8 These complications could occur later in life, possibly in a person’s 20s or 30s, or after kidney transplant.8 If these GI issues become severe, it may be necessary to place a gastronomy tube (G-tube) to make sure that individuals receive necessary nutrition and medications.1,2

Central nervous system effects

The central nervous system (CNS) refers to the brain and spinal cord. The CNS controls all the workings of your body.12 If cystinosis is left uncontrolled, the CNS can calcify, leading to advanced complications. These complications could be benign (not harmful), such as increased pressure, or they could be devastating, with the brain being affected.8

Male hypogonadism

Many males with cystinosis experience hypogonadism, or low testosterone production, because of the buildup of cystine in the testicles. This can lead to infertility.2 It is currently not known if diligent treatment with cystine-depleting medicine can prevent male hypogonadism.8 See the Reproductive health section for more information on this topic.

References

  1. Gahl WA, Thoene JG, Schneider JA. Cystinosis. N Engl J Med. 2002;347(2):111-121.
  2. Nesterova G, Gahl WA. Cystinosis: The evolution of a treatable disease. Pediatr Nephrol. 2013;28:51-59.
  3. John Hopkins Children’s Center. “Hypothyroidism.” Available at http://www.hopkinschildrens.org/hypothyroidism.aspx. Accessed July 29, 2015.
  4. National Institutes of Health, MedlinePlus. “Rickets.” Available at http://www.nlm.nih.gov/medlineplus/ency/article/000344.htm. Accessed July 29, 2015.
  5. National Institutes of Health, MedlinePlus. “Photophobia.” Available at http://www.nlm.nih.gov/medlineplus/ency/article/003041.htm. Accessed July 30, 2015.
  6. Goodyer, Paul. The history of cystinosis: Lessons for clinical management. Int J Nephrol. 2011:1-7. Available at http://www.hindawi.com/journals/ijn/2011/929456/. Accessed August 20, 2012.
  7. Gahl WA, Kuehl EM, Iwata F, et al. Corneal crystals in nephropathic cystinosis: Natural history and treatment with cysteamine eyedrops. Mol Genet Metab. 2000;71:100-120.
  8. Nesterova G, Gahl WA. Cystinosis. National Center for Biotechnology Information. 2014. Available at http://www.ncbi.nlm.nih.gov/books/NBK1400/. Accessed July 29, 2015.
  9. National Institutes of Health, MedlinePlus. “Photophobia.” Available at http://www.nlm.nih.gov/medlineplus/ency/article/003041.htm. Accessed July 30, 2015.
  10. Gahl WA, Balog JZ, Kleta R. Nephropathic cystinosis in adults: Natural history and effects of oral cysteamine therapy. Ann Intern Med. 2007;147:242-250.
  11. National Institutes of Health, MedlinePlus. “Diabetes.” Available at http://www.nlm.nih.gov/medlineplus/diabetes.html. Accessed July 31, 2015.
  12. National Institutes of Health, MedlinePlus. “Central nervous system.” Available at http://www.nlm.nih.gov/medlineplus/ency/article/002311.htm. Accessed July 31, 2015.