Myhre syndrome | |
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Other names | LAPS syndrome, Laryngotracheal stenosis, Arthropathy, Prognathism, and Short stature syndrome [1] |
Myhre syndrome is inherited in an autosomal dominant manner [2] | |
Specialty | Medical genetics |
Myhre syndrome (MS) is an ultrarare genetic disorder caused by dominant gain-of-function (GOF) mutations in the SMAD4 gene. [3] MS mutations are missense heterozygous mutations affecting only Ile500 or Arg496 residues of the SMAD4 protein. [4] MS patients exhibit manifestations of connective tissue disease including dysfunction of the integumentary, cardiovascular, respiratory, gastrointestinal, and musculoskeletal systems and is often characterized by proliferative systemic fibrosis. [5] Some of these features are life threatening, such as airway or arterial narrowing (laryngotracheal stenosis or aortic coarctation) and fibroproliferation of tissues including lung, heart, and liver. [6] Consistent with these clinical observations, cells isolated from patients with MS demonstrate increased TGF-β signaling. [7]
In contrast, loss-of-function (LOF) mutations in SMAD4 predispose individuals to gastrointestinal polyps, a higher risk of colorectal cancer, and a risk of forming arteriovenous malformations (AVM) a hallmark manifestation of hereditary hemorrhagic telangiectasia (HHT). [8] Patients also have external phenotypes similar to Marfan syndrome. [9]
Biologically, SMAD4 plays a prominent role in both canonical TGF-β and other TGF-β superfamily signaling. [10] The systemic manifestations of these two disorders suggest opposite biologic effects, such as the finding of aortic aneurysm in SMAD4-JP-HHT (LOF of SMAD4) versus the aortic hypoplasia seen in Myhre syndrome (GOF in SMAD4). [9]
The clinical presentation is variable but includes: [11] [12] [13] [14] [15] [16]
The facial abnormalities include:
The Musculo-skeletal abnormalities include:
Cardiovascular abnormalities include:
Other anomalies
Myhre syndrome is due to mutations in the SMAD4 gene. [3] This gene encodes a protein - transducer mediating transforming growth factor beta. Some researchers believe that the SMAD4 gene mutations that cause Myhre syndrome impair the ability of the SMAD4 protein to attach (bind) properly with the other proteins involved in the signaling pathway. Other studies have suggested that these mutations result in an abnormally stable SMAD4 protein that remains active in the cell longer. Changes in SMAD4 binding or availability may result in abnormal signaling in many cell types, which affects development of several body systems and leads to the signs and symptoms of Myhre syndrome. [17] [18]
The patients of this disease exhibit hypertrophic phenotype in their muscle tissues. Myostatin target genes are found to be downregulated while bone morphogenetic protein (BMP) target genes display both upregulated and downregulated genotypes. [18]
The diagnosis of Myhre syndrome is established in a proband with characteristic clinical findings and a heterozygous pathogenic (or likely pathogenic) variant in SMAD4 detected by molecular genetic testing. [11] Because Myhre syndrome is typically caused by a de novo pathogenic variant, most probands represent a simplex case (i.e., a single occurrence in a family). [11] Rarely, the family history may be consistent with autosomal dominant inheritance (e.g., affected males and females in multiple generations). [19]
There are currently no disease specific therapies, although the use of losartan has been suggested to prevent fibrosis. [20]
This disorder was first reported in 1981. [21] It has many similarities to LAPS Syndrome and they both arise from the same mutations in the SMAD4 gene. It is believed that they are the same syndrome. [1]
Adams–Oliver syndrome (AOS) is a rare congenital disorder characterized by defects of the scalp and cranium, transverse defects of the limbs, and mottling of the skin.
Tyrosine-protein kinase transmembrane receptor ROR2, also known as neurotrophic tyrosine kinase, receptor-related 2, is a protein that in humans is encoded by the ROR2 gene located on position 9 of the long arm of chromosome 9. This protein is responsible for aspects of bone and cartilage growth. It is involved in Robinow syndrome and autosomal dominant brachydactyly type B. ROR2 is a member of the receptor tyrosine kinase-like orphan receptor (ROR) family.
SMAD4, also called SMAD family member 4, Mothers against decapentaplegic homolog 4, or DPC4 is a highly conserved protein present in all metazoans. It belongs to the SMAD family of transcription factor proteins, which act as mediators of TGF-β signal transduction. The TGFβ family of cytokines regulates critical processes during the lifecycle of metazoans, with important roles during embryo development, tissue homeostasis, regeneration, and immune regulation.
Noonan syndrome with multiple lentigines (NSML) which is part of a group called Ras/MAPK pathway syndromes, is a rare autosomal dominant, multisystem disease caused by a mutation in the protein tyrosine phosphatase, non-receptor type 11 gene (PTPN11). The disease is a complex of features, mostly involving the skin, skeletal and cardiovascular systems, which may or may not be present in all patients. The nature of how the mutation causes each of the condition's symptoms is not well known; however, research is ongoing. It is a RASopathy.
22q13 deletion syndrome, known as Phelan–McDermid syndrome (PMS), is a genetic disorder caused by deletions or rearrangements on the q terminal end of chromosome 22. Any abnormal genetic variation in the q13 region that presents with significant manifestations (phenotype) typical of a terminal deletion may be diagnosed as 22q13 deletion syndrome. There is disagreement among researchers as to the exact definition of 22q13 deletion syndrome. The Developmental Synaptopathies Consortium defines PMS as being caused by SHANK3 mutations, a definition that appears to exclude terminal deletions. The requirement to include SHANK3 in the definition is supported by many but not by those who first described 22q13 deletion syndrome.
Loeys–Dietz syndrome (LDS) is an autosomal dominant genetic connective tissue disorder. It has features similar to Marfan syndrome and Ehlers–Danlos syndrome. The disorder is marked by aneurysms in the aorta, often in children, and the aorta may also undergo sudden dissection in the weakened layers of the wall of the aorta. Aneurysms and dissections also can occur in arteries other than the aorta. Because aneurysms in children tend to rupture early, children are at greater risk for dying if the syndrome is not identified. Surgery to repair aortic aneurysms is essential for treatment.
Arterial tortuosity syndrome is an extremely rare congenital connective tissue condition disorder characterized by tortuosity, elongation, stenosis, or aneurysms in major and medium-size arteries including the aorta.
3C syndrome is a rare condition whose symptoms include heart defects, cerebellar hypoplasia, and cranial dysmorphism. It was first described in the medical literature in 1987 by Ritscher and Schinzel, for whom the disorder is sometimes named.
Vici syndrome, also called immunodeficiency with cleft lip/palate, cataract, hypopigmentation and absent corpus callosum, is a rare autosomal recessive congenital disorder characterized by albinism, agenesis of the corpus callosum, cataracts, cardiomyopathy, severe psychomotor retardation, seizures, immunodeficiency and recurrent severe infections. To date, about 50 cases have been reported.
Fibrillin-1 is a protein that in humans is encoded by the FBN1 gene, located on chromosome 15. It is a large, extracellular matrix glycoprotein that serves as a structural component of 10–12 nm calcium-binding microfibrils. These microfibrils provide force bearing structural support in elastic and nonelastic connective tissue throughout the body. Mutations altering the protein can result in a variety of phenotypic effects differing widely in their severity, including fetal death, developmental problems, Marfan syndrome or in some cases Weill-Marchesani syndrome.
Keutel syndrome (KS) is a rare autosomal recessive genetic disorder characterized by abnormal diffuse cartilage calcification, hypoplasia of the mid-face, peripheral pulmonary stenosis, hearing loss, short distal phalanges (tips) of the fingers and mild mental retardation. Individuals with KS often present with peripheral pulmonary stenosis, brachytelephalangism, sloping forehead, midface hypoplasia, and receding chin. It is associated with abnormalities in the gene coding for matrix gla protein, MGP. Being an autosomal recessive disorder, it may be inherited from two unaffected, abnormal MGP-carrying parents. Thus, people who inherit two affected MGP alleles will likely inherit KS.
A ciliopathy is any genetic disorder that affects the cellular cilia or the cilia anchoring structures, the basal bodies, or ciliary function. Primary cilia are important in guiding the process of development, so abnormal ciliary function while an embryo is developing can lead to a set of malformations that can occur regardless of the particular genetic problem. The similarity of the clinical features of these developmental disorders means that they form a recognizable cluster of syndromes, loosely attributed to abnormal ciliary function and hence called ciliopathies. Regardless of the actual genetic cause, it is clustering of a set of characteristic physiological features which define whether a syndrome is a ciliopathy.
Gerodermia osteodysplastica (GO) is a rare autosomal recessive connective tissue disorder included in the spectrum of cutis laxa syndromes.
X-linked recessive chondrodysplasia punctata is a type of chondrodysplasia punctata that can involve the skin, hair, and cause short stature with skeletal abnormalities, cataracts, and deafness.
Fryns syndrome is an autosomal recessive multiple congenital anomaly syndrome that is usually lethal in the neonatal period. Fryns (1987) reviewed the syndrome.
Distal 18q- is a genetic condition caused by a deletion of genetic material within one of the two copies of chromosome 18. The deletion involves the distal section of 18q and typically extends to the tip of the long arm of chromosome 18.
Aicardi–Goutières syndrome (AGS), which is completely distinct from the similarly named Aicardi syndrome, is a rare, usually early onset childhood, inflammatory disorder most typically affecting the brain and the skin. The majority of affected individuals experience significant intellectual and physical problems, although this is not always the case. The clinical features of AGS can mimic those of in utero acquired infection, and some characteristics of the condition also overlap with the autoimmune disease systemic lupus erythematosus (SLE). Following an original description of eight cases in 1984, the condition was first referred to as 'Aicardi–Goutières syndrome' (AGS) in 1992, and the first international meeting on AGS was held in Pavia, Italy, in 2001.
Omodysplasia type 2 is a very rare genetic disorder characterised by abnormalities in the skull, long bones and genitourinary system.
Cole–Carpenter syndrome is an extremely rare autosomal recessive medical condition in humans. The condition affects less than 10 people worldwide. It is characterised by dysmorphic features and a tendency to fractures.
DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent infections, developmental disability, intellectual disability and cleft palate. Associated conditions include kidney problems, schizophrenia, hearing loss and autoimmune disorders such as rheumatoid arthritis or Graves' disease.
This article incorporates text from the United States National Library of Medicine (), which is in the public domain.
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