Trichorhinophalangeal syndrome type II

Trichorhinophalangeal syndrome type II (TRPS II) is a condition that causes bone and joint malformations; distinctive facial features; intellectual disability; and abnormalities of the skin, hair, teeth, sweat glands, and nails. The name of the condition describes some of the areas of the body that are commonly affected: hair (tricho-), nose (rhino-), and fingers and toes (phalangeal).

People with this condition have multiple noncancerous (benign) bone tumors called osteochondromas. Affected individuals may develop a few to several hundred osteochondromas. These bone growths typically begin in infancy to early childhood and stop forming around adolescence. Depending on the location of the osteochondromas, they can cause pain, limited range of joint movement, or damage to blood vessels or the spinal cord. Individuals with TRPS II may have reduced bone mineral density (osteopenia). Affected individuals often have slow growth before and after birth resulting in short stature. In TRPS II, the ends (epiphyses) of one or more bones in the fingers or toes are abnormally cone-shaped. Additionally, the fingernails and toenails are typically thin and abnormally formed.

Children with TRPS II often have an unusually large range of joint movement (hypermobility). However, as osteochondromas begin to develop, typically starting between infancy and mid-childhood, the joints begin to stiffen, leading to decreased mobility. Individuals with TRPS II may also have a misalignment of the hip joints (hip dysplasia), which often develops in early adulthood but can occur in infancy or childhood.

The characteristic appearance of individuals with TRPS II involves thick eyebrows; a broad nose with a rounded tip; a long, smooth area between the nose and the upper lip (philtrum); a thin upper lip; and small teeth that are either decreased (oligodontia) or increased (supernumerary) in number. Almost all affected individuals have sparse scalp hair. Males are particularly affected by hair loss, with many being nearly or completely bald soon after puberty. Some children with this condition have loose skin, but the skin becomes tighter over time. Individuals with TRPS II may experience excessive sweating (hyperhidrosis).

Most individuals with TRPS II have mild intellectual disability.