MKKS Gene

McKusick-Kaufman syndrome is a condition that affects the development of the hands and feet, heart, and reproductive system. It is characterized by a combination of three features: extra fingers and/or toes (polydactyly), heart defects, and genital abnormalities.

Most females with McKusick-Kaufman syndrome are born with a genital abnormality called hydrometrocolpos, which is a large accumulation of fluid in the pelvis. Hydrometrocolpos results from a blockage of the vagina before birth, which can occur if part of the vagina fails to develop (vaginal agenesis) or if a membrane blocks the opening of the vagina. This blockage allows fluid to build up in the vagina and uterus, stretching these organs and leading to a fluid-filled mass. Genital abnormalities in males with McKusick-Kaufman syndrome can include placement of the urethral opening on the underside of the penis (hypospadias), a downward-curving penis (chordee), and undescended testes (cryptorchidism).

The signs and symptoms of McKusick-Kaufman syndrome overlap significantly with those of another genetic disorder, Bardet-Biedl syndrome. Bardet-Biedl syndrome has several features that are not seen in McKusick-Kaufman syndrome, however. These include vision loss, delayed development, obesity, and kidney (renal) failure. Because some of these features are not apparent at birth, the two conditions can be difficult to tell apart in infancy and early childhood.

Bardet-Biedl syndrome is a disorder that affects many parts of the body. The signs and symptoms of this condition vary among affected individuals, even among members of the same family.

Vision loss is one of the major features of Bardet-Biedl syndrome. Loss of vision occurs as the light-sensing tissue at the back of the eye (the retina) gradually deteriorates. Problems with night vision become apparent by mid-childhood, followed by blind spots that develop in the side (peripheral) vision. Over time, these blind spots enlarge and merge to produce tunnel vision. Most people with Bardet-Biedl syndrome also develop blurred central vision (poor visual acuity) and become legally blind by adolescence or early adulthood.

Obesity is another characteristic feature of Bardet-Biedl syndrome. Abnormal weight gain typically begins in early childhood and continues to be an issue throughout life. Complications of obesity can include type 2 diabetes, high blood pressure (hypertension), and abnormally high cholesterol levels (hypercholesterolemia).

Other major signs and symptoms of Bardet-Biedl syndrome include the presence of extra fingers or toes (polydactyly), intellectual disability or learning problems, and abnormalities of the genitalia. Most affected males produce reduced amounts of sex hormones (hypogonadism), and they are usually unable to father biological children (infertile). Many people with Bardet-Biedl syndrome also have kidney abnormalities, which can be serious or life-threatening.

Additional features of Bardet-Biedl syndrome can include impaired speech, delayed development of motor skills such as standing and walking, behavioral problems such as emotional immaturity and inappropriate outbursts, and clumsiness or poor coordination. Distinctive facial features, dental abnormalities, unusually short or fused fingers or toes, and a partial or complete loss of the sense of smell (anosmia) have also been reported in some people with Bardet-Biedl syndrome. Additionally, this condition can affect the heart, liver, and digestive system.