Proteus syndrome | |
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Other names | Partial gigantism-nevi-hemihypertrophy-macrocephaly syndrome, Wiedemann syndrome |
Alex Green, a 7-year-old boy with Proteus syndrome, confirmed to have the AKT1 p.E17K somatic variant. Alex died at the age of 9. | |
Specialty | Medical genetics |
Proteus syndrome is a rare disorder with a genetic background [1] that can cause tissue overgrowth involving all three embryonic lineages. Patients with Proteus syndrome tend to have an increased risk of embryonic tumor development. [2] The clinical and radiographic symptoms of Proteus syndrome are highly variable, as are its orthopedic manifestations. [3] [4]
Only a few more than 200 cases have been confirmed worldwide, with estimates that about 120 people are currently alive with the condition. [5] As attenuated forms of the disease may exist, there could be many people with Proteus syndrome who remain undiagnosed. Those most readily diagnosed are also the most severely disfigured.
The syndrome is named after the Greek sea-god Proteus, who could change his shape. The condition appears to have been first described in the American medical literature by Samia Temtamy and John Rogers in 1976. [6] [7] American pathologist Michael Cohen described it in 1979. [8]
Proteus syndrome causes an overgrowth of skin, bones, muscles, fatty tissues, and blood and lymphatic vessels. Proteus syndrome is a progressive condition wherein children are usually born without any obvious deformities. Tumors of skin and bone growths appear as they age typically in early childhood. The musculoskeletal manifestations are cardinal for the diagnosis of Proteus syndrome. [3] The severity and locations of these various asymmetrical growths vary greatly but typically the skull, one or more limbs, and soles of the feet will be affected. There is a risk of premature death in affected individuals due to deep vein thrombosis and pulmonary embolism caused by the vessel malformations that are associated with this disorder. Because of carrying excess weight and enlarged limbs, arthritis and muscle pain may also be symptoms. Further risks may occur due to the mass of extra tissue.[ citation needed ]
The disorder itself does not uniformly cause learning impairments: the distribution of intelligence deficits among those with Proteus syndrome appears higher than that of the general population, although this is difficult to determine with statistical significance. [9] In addition, the presence of visible deformity have a negative effect on the social experiences of the affected individual, causing emotional difficulties, social rejection and stigma.[ citation needed ]
Affected individuals are at increased risk for developing certain tumors including unilateral ovarian cystadenomas, testicular tumors, meningiomas, and monomorphic adenomas of the parotid gland.[ citation needed ]
Hemimegalencephaly is often found to be associated. [10]
The musculoskeletal manifestations of Proteus syndrome are frequent and recognizable. Patients tend to demonstrate a unique pattern of skeletal abnormalities. The orthopaedic features are usually bilateral, asymmetrical, progressive and involving all four limbs and spine. Affected patients usually have localized periarticular limb distortions, limb length discrepancy, and spine deformity. Patients with Proteus syndrome can have regular bone configuration and contours despite the bone enlargement. [3] Patients can also exhibit deformation of the skull in the form of dolichocephaly or elongated skull and facial abnormalities. Because of the rarity of the syndrome and the variability of signs, the orthopaedic management should be individualized. [3]
In 2011 researchers determined the cause of Proteus syndrome. In 26 of 29 patients who met strict clinical criteria for the disorder, Lindhurst et al. identified an activating mutation in AKT1 kinase in a mosaic state. [11]
Previous research had suggested the condition linked to PTEN on chromosome 10, [12] while other research pointed to chromosome 16. [13] Prior to the findings regarding AKT1 in 2011, other researchers expressed doubt regarding the involvement of PTEN or GPC3 , which codes for glypican 3 and may play a role in regulating cell division and growth regulation. [14] [15]
Many sources classify Proteus syndrome to be a type of nevus syndrome. The lesions appear to be distributed in a mosaic manner. [20] It has been confirmed that the disorder is an example of genetic mosaicism. [11]
A team of doctors in Australia have trial-tested the drug rapamycin in the treatment of a patient said to have Proteus syndrome and have found it to be an effective remedy. [21] However, the diagnosis of Proteus syndrome in this patient has been questioned by others. [22]
The Proteus syndrome research team in the National Human Genome Research Institute at the United States National Institutes of Health have initiated a Phase 0 dose finding trial with the AKT1 inhibitor ARQ 092, which is being developed by the Arqule Corporation. In earlier tests on tissue and cell samples obtained from patients, ARQ 092 reduced phosphorylation of AKT and downstream targets of AKT in as little as two hours. [23] The Phase 0 trial opened in November 2015. [24] This trial is based on in vitro data showing inhibition of AKT1 in cell lines from patients with Proteus syndrome. [25]
In a 1986 article in the British Medical Journal , Michael Cohen and J.A.R. Tibbles put forward the theory that Joseph Merrick (an Englishman known as the "Elephant Man") had Proteus syndrome. However, the exact condition that Joseph Merrick had is still not known with certainty. [26] [27]
Mandy Sellars has been diagnosed by some doctors as having this condition. [5] Her legs and feet have grown at a disproportionate rate since birth. However, in 2013, Sellars's case was profiled on British television in a special called Shrinking My 17 Stone Legs, in which it was determined that Sellars's condition was not, in fact, Proteus syndrome, but rather the often-misdiagnosed PIK3CA-related overgrowth spectrum, a syndrome caused by a PIK3CA gene mutation.[ citation needed ]
Megalencephaly is a growth development disorder in which the brain is abnormally large. It is characterized by a brain with an average weight that is 2.5 standard deviations above the mean of the general population. Approximately 1 out of 50 children (2%) are said to have the characteristics of megalencephaly in the general population.
A benign tumor is a mass of cells (tumor) that does not invade neighboring tissue or metastasize. Compared to malignant (cancerous) tumors, benign tumors generally have a slower growth rate. Benign tumors have relatively well differentiated cells. They are often surrounded by an outer surface or stay contained within the epithelium. Common examples of benign tumors include moles and uterine fibroids.
Protein kinase B (PKB), also known as Akt, is the collective name of a set of three serine/threonine-specific protein kinases that play key roles in multiple cellular processes such as glucose metabolism, apoptosis, cell proliferation, transcription, and cell migration.
A hamartoma is a mostly benign, local malformation of cells that resembles a neoplasm of local tissue but is usually due to an overgrowth of multiple aberrant cells, with a basis in a systemic genetic condition, rather than a growth descended from a single mutated cell (monoclonality), as would typically define a benign neoplasm/tumor. Despite this, many hamartomas are found to have clonal chromosomal aberrations that are acquired through somatic mutations, and on this basis the term hamartoma is sometimes considered synonymous with neoplasm. Hamartomas are by definition benign, slow-growing or self-limiting, though the underlying condition may still predispose the individual towards malignancies.
Cowden syndrome is an autosomal dominant inherited condition characterized by benign overgrowths called hamartomas as well as an increased lifetime risk of breast, thyroid, uterine, and other cancers. It is often underdiagnosed due to variability in disease presentation, but 99% of patients report mucocutaneous symptoms by age 20–29. Despite some considering it a primarily dermatologic condition, Cowden's syndrome is a multi-system disorder that also includes neurodevelopmental disorders such as macrocephaly.
Phosphatase and tensin homolog (PTEN) is a phosphatase in humans and is encoded by the PTEN gene. Mutations of this gene are a step in the development of many cancers, specifically glioblastoma, lung cancer, breast cancer, and prostate cancer. Genes corresponding to PTEN (orthologs) have been identified in most mammals for which complete genome data are available.
Bannayan–Riley–Ruvalcaba syndrome (BRRS) is a rare overgrowth syndrome and hamartomatous disorder with occurrence of multiple subcutaneous lipomas, macrocephaly and hemangiomas. The disease is inherited in an autosomal dominant manner. The disease belongs to a family of hamartomatous polyposis syndromes, which also includes Peutz–Jeghers syndrome, juvenile polyposis and Cowden syndrome. Mutation of the PTEN gene underlies this syndrome, as well as Cowden syndrome, Proteus syndrome, and Proteus-like syndrome, these four syndromes are referred to as PTEN Hamartoma-Tumor Syndromes.
Simpson–Golabi–Behmel syndrome (SGBS) is a rare inherited congenital disorder that can cause craniofacial, skeletal, vascular, cardiac, and renal abnormalities. There is a high prevalence of cancer associated in those with SGBS which includes wilms tumors, neuroblastoma, tumors of the adrenal gland, liver, lungs and abdominal organs. The syndrome is inherited in an X-linked recessive manner. Females that possess one copy of the mutation are considered to be carriers of the syndrome but may still express varying degrees of the phenotype, suffering mild to severe malady. Males experience a higher likelihood of fetal death.
Pallister–Hall syndrome (PHS) is a rare genetic disorder that affects various body systems. The main features are a non-cancerous mass on the hypothalamus and extra digits (polydactylism). The prevalence of Pallister-Hall Syndrome is unknown; about 100 cases have been reported in publication.
A papillary hidradenoma, also termed hidradenoma papilliferum or mammary-like gland adenoma of the vulva, is a rare, but nonetheless most common benign tumor that occurs in and between anal and genital regions of females. These hidradenomas are sharply circumscribed, nodular tumors that usually develop in women's anogenital area but uncommonly occur in other sites in women and men. Papillary hidradenomas that develop outside of the anogenital region are termed ecctopic papillary hidradenomas or ectopic hidradenoma papilliferums.
Glypicans constitute one of the two major families of heparan sulfate proteoglycans, with the other major family being syndecans. Six glypicans have been identified in mammals, and are referred to as GPC1 through GPC6. In Drosophila two glypicans have been identified, and these are referred to as dally and dally-like. One glypican has been identified in C. elegans. Glypicans seem to play a vital role in developmental morphogenesis, and have been suggested as regulators for the Wnt and Hedgehog cell signaling pathways. They have additionally been suggested as regulators for fibroblast growth factor and bone morphogenic protein signaling.
RAC(Rho family)-alpha serine/threonine-protein kinase is an enzyme that in humans is encoded by the AKT1 gene. This enzyme belongs to the AKT subfamily of serine/threonine kinases that contain SH2 protein domains. It is commonly referred to as PKB, or by both names as "Akt/PKB".
Glypican-3 is a protein that, in humans, is encoded by the GPC3 gene. The GPC3 gene is located on human X chromosome (Xq26) where the most common gene encodes a 70-kDa core protein with 580 amino acids. Three variants have been detected that encode alternatively spliced forms termed Isoforms 1 (NP_001158089), Isoform 3 (NP_001158090) and Isoform 4 (NP_001158091).
Lhermitte–Duclos disease (LDD), also called dysplastic gangliocytoma of the cerebellum (DGC), is a rare, slowly growing tumor of the cerebellum, a gangliocytoma sometimes considered to be a hamartoma, characterized by diffuse hypertrophy of the granular layer of the cerebellum. It is often associated with Cowden syndrome. It was described by Jacques Jean Lhermitte and P. Duclos in 1920.
Overgrowth syndromes in children constitute a group of rare disorders that are characterised by tissue hypertrophy. Individual overgrowth syndromes have been shown to overlap with regard to clinical and radiologic features. The details of the genetic bases of these syndromes are unfolding. Any of the three embryonic tissue layers may be involved. The syndromes may manifest in localized or generalized tissue overgrowth. Latitudinal and longitudinal growth may be affected. Nevertheless, the musculoskeletal features are central to the diagnosis of some syndromes such as Proteus syndrome.
The PI3K/AKT/mTOR pathway is an intracellular signaling pathway important in regulating the cell cycle. Therefore, it is directly related to cellular quiescence, proliferation, cancer, and longevity. PI3K activation phosphorylates and activates AKT, localizing it in the plasma membrane. AKT can have a number of downstream effects such as activating CREB, inhibiting p27, localizing FOXO in the cytoplasm, activating PtdIns-3ps, and activating mTOR which can affect transcription of p70 or 4EBP1. There are many known factors that enhance the PI3K/AKT pathway including EGF, shh, IGF-1, insulin, and calmodulin. Both leptin and insulin recruit PI3K signalling for metabolic regulation. The pathway is antagonized by various factors including PTEN, GSK3B, and HB9.
Macrocephaly-capillary malformation (M-CM) is a multiple malformation syndrome causing abnormal body and head overgrowth and cutaneous, vascular, neurologic, and limb abnormalities. Though not every patient has all features, commonly found signs include macrocephaly, congenital macrosomia, extensive cutaneous capillary malformation, body asymmetry, polydactyly or syndactyly of the hands and feet, lax joints, doughy skin, variable developmental delay and other neurologic problems such as seizures and low muscle tone.
CLOVES syndrome is a rare overgrowth syndrome with complex vascular anomalies. CLOVES syndrome affects people with various symptoms, ranging from mild fatty soft-tissue tumors to vascular malformations encompassing the spine or internal organs.
Facial infiltrating lipomatosis (FIL), also referred to as congenital infiltrating lipomatosis of the face or facial infused lipomatosis, is an ultra-rare craniofacial overgrowth condition caused by a genetic mutation of the PIK3CA gene. The condition is a part of the PIK3CA related overgrowth spectrum (PROS). The disease is congenital and non-hereditary. First described by Slavin and colleagues in 1983.
Papillomatosis of the breast (PB) is a rare, benign, epitheliosis-like lesion, i.e. an overgrowth of the cells lining the ducts of glands that resembles a papilla or nipple-like nodule/tumor. PB tumors develop in the apocrine glands of the breast. PB is also termed juvenile papillomatosis because of its frequent occurrence in younger women and Swiss cheese disease because of its microscopic appearance. Rarely, PB has also been diagnosed in very young, adolescent, and adult males.
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