McKusick-Kaufman syndrome

McKusick-Kaufman syndrome is a condition that affects the development of the hands, feet, heart, and reproductive system. It is characterized by a combination of three features: extra fingers and/or toes (polydactyly), congenital heart defects, and genital abnormalities. The most common genital abnormality is hydrometrocolpos, an accumulation of fluid in the vagina and uterus.

In people with McKusick-Kaufman syndrome, the extra digits are typically on the same side of the hand or foot as the pinky or little toe (postaxial polydactyly). The congenital heart defects in individuals with McKusick-Kaufman syndrome can include an atrial septal defect or a ventricular septal defect, which are openings in the wall (septum) that separates the upper or lower chambers of the heart. 

A genital abnormality called hydrometrocolpos is common in individuals with McKusick-Kaufman syndrome. Hydrometrocolpos can occur if part of the vagina  fails to develop (vaginal agenesis) or if a membrane blocks the opening of the vagina. The blockage allows fluid to build up in the vagina and uterus, stretching these organs and leading to a fluid-filled mass. Other genital abnormalities associated with McKusick-Kaufman syndrome can include a 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. However, Bardet-Biedl syndrome has several features that are not typically seen in people with McKusick-Kaufman syndrome. These include a gradual loss of vision, developmental disabilities, kidney abnormalities, and obesity. Because some of these features are not apparent at birth, the two conditions can be difficult to tell apart in infancy and early childhood.

Both McKusick-Kaufman syndrome and Bardet-Biedl syndrome belong to a group of conditions called ciliopathies. Ciliopathies are inherited disorders that affect the structure or function of cilia, the microscopic, finger-like projections found on the surface of cells. Cilia are involved in signaling pathways that transmit information between cells.