Cystinosis glossary—words to know

Sometimes medical terms can be difficult to understand. But learning the words used to talk about cystinosis can help you be clear with your doctor, family, and friends. This glossary is a great place to start.

Amino acid: A building block of proteins used in every cell to help the body grow.

Cystine: The amino acid that builds up inside of cells when a person has cystinosis.

Cystine-depleting therapy (CDT): A treatment that works to reduce the buildup of cystine in cells. Learn how taking a CDT as prescribed can help keep cystine levels low around the clock.

Cystine level test: A blood test that measures the amount of cystine in white blood cells at a given time. There are 2 tests that can measure your cystine levels: mixed leukocytes and granulocytes.

Dialysis: A medical treatment to clean the blood when the kidneys do not work as they should.

Fanconi syndrome: A kidney disorder that causes the body to lose important substances needed for good health. It causes extreme thirst and frequent peeing (urination).

Granulocyte: A type of white blood cell that is collected in a blood sample during cystine level testing.

Hypothyroidism: A condition in which the thyroid gland is unable to make enough thyroid hormone, causing the body to not work like it should. Common symptoms include but are not limited to slowed growth, tiredness, and weight gain.

Immune system: A group of cells that protect the body against attacks by germs.

Infertility: Inability to cause pregnancy (for men) or inability to get pregnant (for women). Women of childbearing age with cystinosis may become pregnant.

Kidney transplant: A surgery to place a healthy kidney from a donor into the body of a person with failing kidneys.

Leukocytes: Commonly referred to as white blood cells; a collection of cells that help the body fight infections. One of the 2 available cystine level tests collects leukocytes in a blood sample.

Lysosome: The part of a cell that acts as a “recycling center” by breaking down proteins into amino acids This is the part of the cell where cystine becomes trapped and builds up in people with cystinosis.

Myopathy: A disease that affects the muscles, making a person feel very weak.

Nephropathic cystinosis: Cystinosis of the kidney; often called classic infantile cystinosis because its symptoms usually appear within a child's first year of life. This is the most common (95% of all cases) and most severe form of cystinosis.

Photophobia: In patients with cystinosis, a buildup of cystine in the eyes may result in light sensitivity, or the eye's inability to tolerate light. It may also cause eye pain and severe headaches.

Rickets: Softening and weakening of bones in children, usually caused by a lack of vitamin D (phosphate) in the body.

White blood cells (WBCs): Also called leukocytes; a collection of cells that help the body fight infections.