Homocystinuria is a rare genetic disorder that affects the body's ability to process certain amino acids, particularly methionine. This condition is caused by a deficiency in the enzyme cystathionine beta-synthase, which leads to the accumulation of homocysteine in the blood and urine. Symptoms can include developmental delays, vision problems, and an increased risk of blood clots. Diagnosis typically involves blood tests to measure homocysteine levels and genetic testing to identify mutations. Treatment often includes a special diet low in methionine, vitamin supplements, and medications to help lower homocysteine levels, aiming to prevent complications and improve quality of life.