Coffin–Lowry syndrome is a
genetic disorder
A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders ...
that is
X-linked dominant and which causes severe mental problems sometimes associated with abnormalities of growth, cardiac abnormalities,
kyphoscoliosis, and auditory and visual abnormalities.
Presentation
Symptoms of disease are more severe in males, who are generally diagnosed in early childhood. Children with CLS display cognitive disabilities of varying severity. Additional neuromuscular features include
sleep apnea
Sleep apnea (sleep apnoea or sleep apnœa in British English) is a sleep-related breathing disorder in which repetitive Apnea, pauses in breathing, periods of shallow breathing, or collapse of the upper airway during sleep results in poor vent ...
, muscular spasticity, progressive loss of muscle strength and tone leading to
paraplegia
Paraplegia, or paraparesis, is an impairment in motor or sensory function of the lower extremities. The word comes from Ionic Greek ()
"half-stricken". It is usually caused by spinal cord injury or a congenital condition that affects the neura ...
or partial paralysis. Affected individuals are at elevated risk of
stroke
Stroke is a medical condition in which poor cerebral circulation, blood flow to a part of the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemor ...
. Some patients experience stimulus-induced drop attacks (SIDAs, temporary paralytic episodes without loss of consciousness), triggered by unpredictable environmental stimuli (touch, scents, sounds, etc.).
SIDA episodes become more frequent as the disease progresses, and become frequent around adolescence in males.
Additional clinical physical features include small, soft hands with tapered fingers. Distinct facial architecture such as a flattened nose, widely separated and downward sloping eyes, a prominent forehead, and a wide mouth with large lips are reported as coincident facial features in patients with the disorder.
Some individuals experience hearing loss.
Others display
kyphoscoliosis (multidirectional curvature of the spine) which can lead to difficulty with breathing and/or
pulmonary hypertension
Pulmonary hypertension (PH or PHTN) is a condition of increased blood pressure in the pulmonary artery, arteries of the lungs. Symptoms include dypsnea, shortness of breath, Syncope (medicine), fainting, tiredness, chest pain, pedal edema, swell ...
.
Cardiorespiratory complications may arise, which is why it is recommended that CLS patients undergo regular monitoring for spinal irregularities. Physical exams, CT imaging and X-ray imaging are standard methods of assessment.
Causes
The syndrome is caused by
mutation
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...
s in the
RPS6KA3 gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
. This gene is located on the short arm of the
X chromosome
The X chromosome is one of the two sex chromosomes in many organisms, including mammals, and is found in both males and females. It is a part of the XY sex-determination system and XO sex-determination system. The X chromosome was named for its u ...
(Xp22.2). The RPS6KA3 gene makes a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
that is involved with
signaling within cells. Researchers believe that this protein helps control the activity of other genes and plays an important role in the brain. The protein is involved in cell signaling pathways that are required for learning, the formation of long-term memories, and the survival of nerve cells. The protein RSK2 which is encoded by the RPS6KA3 gene is a
kinase
In biochemistry, a kinase () is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule don ...
which phosphorylates some substrates like
CREB
CREB-TF (CREB, cAMP response element-binding protein) is a cellular transcription factor. It binds to certain DNA sequences called cAMP response elements (CRE), thereby increasing or decreasing the transcription of the genes. CREB was first des ...
and
histone H3
Histone H3 is one of the five main histones involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and a long N-terminal end, N-terminal tail, H3 is involved with the structure of the nucleosomes of the 'b ...
. RSK2 is involved at the distal end of the
Ras/MAPK signaling pathway. Mutations in the RPS6KA3 disturb the function of the protein, but it is unclear how a lack of this protein causes the signs and symptoms of Coffin–Lowry syndrome. At this time more than 120 mutations have been found.
[ Some people with the features of Coffin–Lowry syndrome do not have identified mutations in the RPS6KA3 gene. In these cases, the cause of the condition is unknown.
This condition is inherited in an X-linked dominant pattern. A condition is considered X-linked if the gene that causes the disorder is located on the X chromosome (one of the two sex chromosomes). The inheritance is dominant if one copy of the altered gene is sufficient to cause the condition.
A majority of boys with Coffin–Lowry syndrome have no history of the condition in their families. These cases are caused by new mutations in the RPS6KA3 gene (de novo mutations). A new mutation means that neither parent has the altered gene, but the affected individual could pass it on to his children.
]
Genetics
Coffin–Lowry syndrome is an X-linked disorder resulting from loss-of-function mutations in the RPS6KA3 gene, which encodes RSK2 ( ribosomal S6 kinase 2). Multiple mutations have been identified in RPS6KA3 that can give rise to the disorder, including missense mutation
In genetics, a missense mutation is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid. It is a type of nonsynonymous substitution. Missense mutations change amino acids, which in turn alt ...
s, nonsense mutations, insertions and deletions. Individuals with CLS rarely have affected parents, suggesting that most incidents arise from de novo mutation
A de novo mutation (DNM) is any mutation or alteration in the genome of an individual organism (human, animal, plant, microbe, etc.) that was not inherited from its parents. This type of mutation spontaneously occurs during the process of DNA repl ...
s in the germline. The lack of an inheritance pattern may be due to the fact that affected individuals are unlikely to parent children. In 20–30% of cases, however, there is a family history of disease. In these cases, the disorder is typically inherited from the maternal parent. Because RPS6KA3 is located on the X chromosome, males (who possess only one copy of the X chromosome) display more severe symptoms than females. Affected females usually possess one mutated copy of the RPS6KA3 gene and one wild type copy. Random inactivation of one copy of the X chromosome in females mitigates the impact of possessing a mutant allele. Occasionally females are born with two mutated alleles. In these cases the symptoms are as severe as in males with the disease.[Marques Pereira, P., Schneider, A., Pannetier, S. et al. "Coffin–Lowry syndrome". ''European Journal of Human Genetics'' 18, 627–633 (2010). ]
Cell physiology
Mutations in the RPS6KA3 gene can result in expression of an RSK2 protein (ribosomal S6 kinase 2) with reduced or absent kinase function. RSK2 is a downstream component of the MAPK (mitogen-activated protein kinase
A mitogen-activated protein kinase (MAPK or MAP kinase) is a type of serine/threonine-specific protein kinases involved in directing cellular responses to a diverse array of stimuli, such as mitogens, osmotic stress, heat shock and proinflamma ...
) cascade that is itself a kinase. RSK2 phosphorylates cellular proteins (including histone H3, and CREB), which regulate eukaryotic gene expression. In individuals with Coffin–Lowry syndrome, phosphorylation of transcriptional regulators is reduced due to the weakened activity of RSK2 kinase activity. RSK2 is normally activated by the ERK MAP kinase. Mutated RSK2 may be deficient for activation by ERK, or its kinase activity may be reduced despite activation by ERK. The most common mutation in RPS6KA3 is an early stop codon that fails to produce a functional protein, indicating that disease etiology most likely arises from loss-of-function effects. Substitution mutations (which alter a single amino acid) have also been shown to give rise to the disease. RSK2 is highly expressed in the brain, specifically in the neocortex
The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, ...
, hippocampus
The hippocampus (: hippocampi; via Latin from Ancient Greek, Greek , 'seahorse'), also hippocampus proper, is a major component of the brain of humans and many other vertebrates. In the human brain the hippocampus, the dentate gyrus, and the ...
, and Purkinje cell
Purkinje cells or Purkinje neurons, named for Czech physiologist Jan Evangelista Purkyně who identified them in 1837, are a unique type of prominent, large neuron located in the Cerebellum, cerebellar Cortex (anatomy), cortex of the brain. Wi ...
s, all of which are involved in cognitive function and behavior. There is some experimental evidence that RSK2 regulates synaptic transmission and plasticity in neuronal cell types.
Diagnosis
Affected individuals are often short in stature. Behavioral symptoms include aggression and depression, but these may be secondary to the emotional consequences of significant physical disabilities associated with the disorder.[Rogers RC, Abidi FE]
''Coffin–Lowry Syndrome''
16 July 2002 pdated 1 February 2018. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. ''GeneReviews'' [Internet Seattle, Washington: University of Washington, Seattle.
Coffin–Lowry patients may be affected by chewing and swallowing difficulties, for which there are diagnostic assessments. Among these are the Videofluoroscopic Swallowing Evaluation (VFSE), the Karaduman Chewing Performance Scale, and the Penetration Aspiration Scale (PAS) which is used to evaluate accidental aspiration of food particles. The Pediatric Assessment Tool (PEDI-EAT-10) also includes measurement of severity of dysphagia (difficulty in swallowing). Molecular genetic testing can be used to confirm the genetic diagnosis of Coffin–Lowry syndrome or to assess pregnancy risk in affected families.
Symptoms table:
* Generally symptoms listed as "rare" are common in more severe cases.
Imaging studies
X-ray and neuroimaging studies may be helpful in confirming a diagnosis of Coffin–Lowry syndrome. Decreased ribosomal S6 kinase activity in cultured fibroblast or transformed lymphoblast cells from a male indicates Coffin–Lowry syndrome. Studies of enzyme activity can not be used to diagnose an affected female.
Molecular genetic testing on a blood specimen or cells from a cheek swab is available to identify mutations in the RSK2 gene. This testing can be used to confirm but not rule out the diagnosis of Coffin–Lowry syndrome because not all affected individuals have a detectable mutation.
Treatment
There is no cure for Coffin–Lowry syndrome. Clinical objectives are centered on symptom management. Because stimulus-induced drop attacks (SIDAs) can result in physical harm to patients with the disorder, the use of medication to prevent or reduce the number of SIDA episodes is a safety priority. Physical precautionary measures have also been used to protect patients from injury, including the use of a helmet or a wheelchair. Because sudden excitement or fright can trigger a SIDA episode it is important to minimize exposure to startling stimuli. Medications prescribed include benzodiazepines
Benzodiazepines (BZD, BDZ, BZs), colloquially known as "benzos", are a class of central nervous system (CNS) depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat co ...
(tranquilizers used to treat anxiety), valproate (used to manage epilepsy
Epilepsy is a group of Non-communicable disease, non-communicable Neurological disorder, neurological disorders characterized by a tendency for recurrent, unprovoked Seizure, seizures. A seizure is a sudden burst of abnormal electrical activit ...
and bipolar disorder
Bipolar disorder (BD), previously known as manic depression, is a mental disorder characterized by periods of Depression (mood), depression and periods of abnormally elevated Mood (psychology), mood that each last from days to weeks, and in ...
), and selective serotonin reuptake inhibitors
Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions.
SSRIs primarily work by blo ...
(SSRIs) (used to treat major depression). When affected individuals display aggressive or destructive behavior that could harm themselves or others, the antipsychotic medication risperidone
Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder, as well as aggressive and self-injurious behaviors associated with autism spectrum disorder. It is t ...
may eventually be prescribed. It is recommended that spinal development be monitored regularly by X-ray and physical exams. Echocardiograms are recommended every 5–10 years to assess cardiac function and development. Families are encouraged to receive genetic counseling in order to understand and prepare to provide care for children affected by Coffin–Lowry syndrome.
Prognosis
Lifespan may be significantly shortened in males with Coffin–Lowry syndrome. Patients may survive into their late twenties, but generally die young due to cardiac, respiratory, and post-operative complications. The progression of reduced cardiac functioning over time may necessitate surgical procedures to counteract mitral valve
The mitral valve ( ), also known as the bicuspid valve or left atrioventricular valve, is one of the four heart valves. It has two Cusps of heart valves, cusps or flaps and lies between the atrium (heart), left atrium and the ventricle (heart), ...
dysfunction, congenital heart disease, patent ductus arteriosus
Patent ductus arteriosus (PDA) is a medical condition in which the ''ductus arteriosus'' fails to close after childbirth, birth: this allows a portion of oxygenated blood from the left heart to flow back to the lungs from the aorta, which has a h ...
, and ventricular hypertrophy. Kyphoscoliosis may worsen over time and contribute to these pathologies.
Epidemiology
The prevalence of CLS is uncertain due to the rarity of the disease, but CLS is estimated to affect between 1 in 50,000 and 1 in 100,000 people. Prenatal testing is available to test for CLS of an offspring if a family member has been diagnosed with CLS.
History
Coffin–Lowry was first described by Grange S. Coffin (b. 1923) in 1966 and independently by Robert Brian Lowry (b. 1932) in 1971. Dr. Temtamy showed that the cases represented a single syndrome in 1975.
In 1972, Peter G. Procopis and B. Turner published a case study on a family of four brothers with Coffin-Lowry Syndrome, with female relatives, specifically sisters, only possessing some mild deformities and abnormalities. In 1975, Samia Temtamy reported eight patients from three different families displaying symptoms of Coffin-Lowry Syndrome, suggesting that the disorder is more common than believed and often goes underdiagnosed. On the basis of these reports, AG Hunter, Simone Gilgenkrantz, and ID Young established Coffin-Lowry Syndrome as a novel medical diagnosis and named it for the two doctors to originally describe its clinical symptoms.
Additional case studies have since expanded the original list of clinical signs and symptoms. In 2002, Helen Fryssira and RJ Simensen identified a 3 base pair deletion in the gene encoding RSK2, which was the first report of the gene responsible for Coffin-Lowry.
Culture
The Coffin–Lowry Syndrome Foundation acts as a clearinghouse for information on Coffin–Lowry syndrome and hosts a forum for affected families. The family matching program facilitates community building and resource sharing for recent diagnoses.
The Coffin-Lowry Syndrome Foundation was created in 1991. The mission of the Foundation is to provide informational links, resources, and databases to families and patients dealing with the disease and enables them to communicate with one another. Families and patients can share their experiences and retrieve advice on the foundation's online site as well as locate helpful services, telephone support, and day-to-day news on medical progress into understanding and treating those affected by Coffin-Lowry Syndrome. The symbol of the foundation is an apple, chosen for its representation of knowledge, feminine beauty, immortality, rebirth, and peace. The foundation provides a support network and source of hope for the families of patients with Coffin-Lowry Syndrome.
References
Sources
''This article incorporates public domain text fro
The U.S. National Library of Medicine
and th
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External links
GeneReviews/UW/NIH entry on Coffin–Lowry syndrome
Coffin-Lowry syndrome: MedlinePlus Genetics
{{DEFAULTSORT:Coffin-Lowry syndrome
Deficiencies of intracellular signaling peptides and proteins
Rare genetic syndromes
Syndromes affecting the heart