Trichorhinophalangeal syndrome, or TRPS, is an uncommon genetic condition that influences the development of bones and cartilage, leading to distinct physical characteristics. The name combines “tricho” for hair, “rhino” for the nose, and “phalangeal” for the bones of the fingers and toes. These areas, along with overall stature, are the most noticeably impacted parts of the body.
Genetic Causes and Types of TRPS
The root cause of TRPS lies within mutations of the TRPS1 gene, located on chromosome 8. This gene provides instructions for making a protein that plays a role in the formation of bone, cartilage, and hair follicles. When the TRPS1 gene is altered, this protein cannot function correctly, disrupting normal development in these tissues.
The condition is inherited in an autosomal dominant pattern, meaning inheriting just one copy of the mutated gene from a parent is enough to cause the disorder. In many instances, the genetic change is not inherited but occurs as a new, or de novo, mutation in an individual with no family history of the syndrome.
There are three recognized classifications of TRPS. Type I is caused by a mutation within the TRPS1 gene itself and is the most common form. A more complex form, Type II, is also known as Langer-Giedion syndrome and results from a larger piece of missing genetic material on chromosome 8 that includes both the TRPS1 and EXT1 genes.
The loss of the EXT1 gene contributes to additional skeletal issues not seen in Type I. A third classification, Type III, is also caused by mutations in the TRPS1 gene but results in more severe short stature and shortening of the fingers and toes. Because of the shared genetic cause, some classifications consider Type III a more severe presentation on the spectrum of Type I.
Recognizable Symptoms and Physical Features
Individuals with TRPS have sparse, fine, and slow-growing scalp hair. Eyebrows may also be sparse, particularly in the outer portions. These signs extend to the nails, which can be thin or abnormally formed.
A prominent, pear-shaped or bulbous nose is a hallmark of the syndrome. This is often accompanied by a long, flat philtrum—the vertical groove between the base of the nose and the upper lip—and a thin upper lip. Large or prominent ears are also a common finding.
Skeletal abnormalities primarily affect the hands and feet, with short fingers and toes (brachydactyly) being common. X-rays often reveal cone-shaped epiphyses, which are the growing ends of the bones in the fingers and toes. This unusual cone shape can cause the fingers to deviate sideways.
People with TRPS often have short stature. Joint problems are also prevalent, including hypermobility in childhood that can transition to pain and stiffness in adulthood. Hip dysplasia is a frequent concern, and those with Type II also develop multiple benign bony growths called osteochondromas due to the deletion of the EXT1 gene.
The Diagnostic Process
A TRPS diagnosis begins with a clinical evaluation by a physician. This involves assessing the individual’s physical traits, reviewing growth patterns, and taking a family medical history.
Radiographic imaging is also used, especially X-rays of the hands and feet, to look for underlying skeletal markers. The most notable finding is the presence of cone-shaped epiphyses in the phalanges. This specific abnormality is a strong indicator of the syndrome.
Confirmation of a TRPS diagnosis comes from molecular genetic testing. A blood sample is analyzed to identify a mutation in the TRPS1 gene or, for suspected Type II cases, a larger deletion including the EXT1 gene. A positive genetic test provides a conclusive diagnosis and helps classify the TRPS type.
Management and Supportive Care
Since there is no cure for TRPS, management focuses on addressing specific symptoms to improve quality of life. This requires a multidisciplinary team of specialists to monitor and treat the various health issues associated with the condition.
Orthopedic care is a primary component of management. This includes regular monitoring of the joints, especially the hips, for signs of dysplasia or early-onset osteoarthritis. For the painful bony growths (exostoses) seen in TRPS Type II, surgical removal may be recommended, and severe hip dysplasia may require hip replacement surgery.
Physical and occupational therapies help maintain function, manage joint pain, preserve mobility, and assist with fine motor skills. For chronic pain from joint and bone issues, management may include non-steroidal anti-inflammatory drugs (NSAIDs) or other non-opioid analgesics.
Other aspects of health also require specialized attention. Growth patterns are monitored, and in some cases of documented growth hormone deficiency, hormone therapy may be considered. Due to potential dental anomalies like extra teeth, specialized dental and orthodontic care is often necessary. Some individuals may also find practical advice on hair care or the use of wigs to be beneficial.