What is Proteus syndrome

TL;DR: Proteus syndrome is an extremely rare, non-hereditary condition characterized by the progressive, disproportionate overgrowth of various body tissues, including skin, bone, and adipose tissue. Because the condition is mosaic, symptoms vary widely between individuals, often requiring a multidisciplinary medical approach to manage complex physical manifestations.

What is Proteus syndrome and how does it affect the body?

Proteus syndrome is a complex disorder that causes localized overgrowth of tissue, meaning only certain parts of the body are affected while others develop normally. This overgrowth is usually asymmetric and progressive, often becoming more pronounced as a child grows. The condition can impact nearly any system in the body, most notably causing skeletal deformities, thick skin growths (such as cerebriform connective tissue nevi), and vascular malformations. Because Proteus syndrome is a mosaic disorder, no two patients experience the exact same clinical presentation, making personalized care essential.

What causes Proteus syndrome?

The biological mechanism behind Proteus syndrome involves a somatic mutation in the AKT1 gene. Crucially, this mutation occurs after conception, which is why the condition is not inherited from parents. This mutation leads to abnormal cell survival and proliferation, resulting in the irregular tissue growth observed in patients. Because this mutation is "mosaic," it is only present in some of the body's cells, which explains why the disease does not affect every organ or tissue uniformly.

What are the primary clinical features of Proteus syndrome?

The manifestations of Proteus syndrome are diverse and often evolve over time. Clinical diagnosis is typically based on a specific set of criteria that distinguish it from other overgrowth syndromes. Common features include:

• Cerebriform connective tissue nevi: Distinctive, thick, raised skin lesions that often resemble the surface of a brain.


• Skeletal overgrowth: Disproportionate bone growth, which can lead to limb length discrepancy, scoliosis, or joint deformities.


• Vascular malformations: Abnormal connections between blood vessels, which carry a risk of deep vein thrombosis (DVT) and pulmonary embolism.


• Adipose tissue dysregulation: Either excessive growth of fatty tissue (lipomas) or a complete lack of fat in certain areas.

How rare is Proteus syndrome?

Proteus syndrome is exceedingly rare; it is estimated that fewer than 100 cases have been documented in medical literature, though this likely underrepresents the true prevalence due to diagnostic challenges. It affects males and females equally, and there is no known geographic, ethnic, or racial predilection. Onset typically occurs in early childhood, though symptoms may be subtle at birth and become more apparent as the child develops.

How is Proteus syndrome differentiated from other conditions?

It is common for Proteus syndrome to be confused with other overgrowth disorders, such as CLOVES syndrome or Klippel-Trenaunay syndrome. The key differentiator is the specific combination of the AKT1 mutation and the presence of cerebriform connective tissue nevi. Unlike many other genetic conditions, Proteus syndrome is not passed down through families, providing reassurance to parents that they are not carriers of the mutation.

Next steps

• Consult with a geneticist or a specialist in pediatric overgrowth disorders to confirm a diagnosis via molecular testing.


• Connect with the DiseaseMaps.org community to share experiences with the 5 members currently mapped with this condition.


• Establish a multidisciplinary care team, including orthopedists, dermatologists, and vascular specialists, to monitor for potential complications like blood clots.


• Visit the NIH Genetic and Rare Diseases (GARD) Information Center for the most up-to-date clinical trial information.

Medical Disclaimer: This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the advice of your physician or other qualified health provider with any questions regarding a medical condition.

References

• NIH Genetic and Rare Diseases (GARD) Information Center: Proteus Syndrome Overview


• Orphanet: Proteus Syndrome (ORPHA:744)


• OMIM (Online Mendelian Inheritance in Man): Proteus Syndrome (#176920)


• The Proteus Syndrome Foundation