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Smith-Magenis syndrome


Other Names for this Disease

  • Chromosome 17p11.2 deletion syndrome
  • SMS
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Overview

What is Smith-Magenis syndrome?

What are the signs and symptoms of Smith-Magenis syndrome?

What causes Smith-Magenis syndrome?

Is Smith-Magenis syndrome inherited?

¿Qué es el síndrome de Smith-Magenis?

¿Cuál es la causa del síndrome de Smith-Magenis?

¿Cuáles son las señales y síntomas del síndrome de Smith-Magenis?

¿Cómo puede ser tratado el síndrome de Smith-Magenis?

¿Cómo es el diagnóstico del síndrome de Smith-Magenis?

What is Smith-Magenis syndrome?

Smith-Magenis syndrome is a developmental disorder that affects many parts of the body. The major features of this condition include mild to moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioral problems. Most people with Smith-Magenis syndrome have a deletion of genetic material from a specific region of chromosome 17. Although this region contains multiple genes, researchers believe that the loss of one particular gene, RAI1, in each cell is responsible for most of the characteristic features of the condition. Smith-Magenis syndrome is not typically inherited, but results from a genetic change that occurs during the formation of reproductive cells (eggs or sperm) or in early fetal development.[1]
Last updated: 8/22/2014

What are the signs and symptoms of Smith-Magenis syndrome?

The major features of Smith-Magenis syndrome include mild to moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioral problems.[1]

Most people with Smith-Magenis syndrome have a broad, square-shaped face with deep-set eyes, full cheeks, and a prominent lower jaw. The middle of the face and the bridge of the nose often appear flattened. The mouth tends to turn downward with a full, outward-curving upper lip. These facial differences can be subtle in early childhood, but they usually become more distinctive in later childhood and adulthood. Dental abnormalities are also common in affected individuals.[1]

Disrupted sleep patterns are characteristic of Smith-Magenis syndrome, typically beginning early in life. Affected people may be very sleepy during the day, but have trouble falling asleep and awaken several times each night.[1]

People with Smith-Magenis syndrome have affectionate, engaging personalities, but most also have behavioral problems. These include frequent temper tantrums and outbursts, aggression, anxiety, impulsiveness, and difficulty paying attention. Self-injury, including biting, hitting, head banging, and skin picking, is very common. Repetitive self-hugging is a behavioral trait that may be unique to Smith-Magenis syndrome. People with this condition also compulsively lick their fingers and flip pages of books and magazines (a behavior known as 'lick and flip').[1]

Other signs and symptoms of Smith-Magenis syndrome include short stature, abnormal curvature of the spine (scoliosis), reduced sensitivity to pain and temperature, and a hoarse voice. Some people with this disorder have ear abnormalities that lead to hearing loss. Affected individuals may have eye abnormalities that cause nearsightedness (myopia) and other vision problems. Although less common, heart and kidney defects also have been reported in people with Smith-Magenis syndrome.[1]

Last updated: 8/22/2014

What causes Smith-Magenis syndrome?

Most people with Smith-Magenis syndrome have a deletion of genetic material from a specific region of chromosome 17.[1][2] Although this region contains multiple genes, researchers believe that the loss of one particular gene, RAI1, is responsible for most of the characteristic features of this condition. The loss of other genes in the deleted region may explain why there is variability in features among affected individuals.[1] A small percentage of people with Smith-Magenis syndrome have just a mutation in the RAI1 gene (not a deletion of the larger part of the chromosome).[1][2] Although these individuals have many of the major features of the condition, they are less likely than people with a chromosomal deletion to have short stature, hearing loss, and heart or kidney abnormalities.[1]
Last updated: 2/15/2012

Is Smith-Magenis syndrome inherited?

Smith-Magenis syndrome is not typically inherited. The condition usually results from a genetic change that occurs during the formation of reproductive cells (eggs or sperm) or in early fetal development. Most often, people with Smith-Magenis syndrome have no history of the condition in their family.[1][2] In a very small number of cases, parental mosaicism has been reported. Complex familial chromosomal rearrangements leading to deletion of chromosome 17p11.2 and Smith-Magenis syndrome have also been reported. Again, these are very rare. As a result, chromosome analysis of the parents is suggested for all newly diagnosed individuals. This information can help to identify specific risks to other family members. For instance, if a parent of an individual with Smith-Magenis syndrome has a balanced chromosome rearrangement, at-risk family members (siblings, etc.) can be tested by chromosome analysis and FISH.[2]
Last updated: 2/15/2012

¿Qué es el síndrome de Smith-Magenis?

El síndrome de Smith-Magenis es un trastorno genético que afecta muchos órganos y sistemas del cuerpo y que se debe a una delección (pérdida) de material genético en una región especifica del cromosoma 17. Se caracteriza por un atraso intelectual moderado, atraso en el lenguaje y algunas características del rostro que son distintivas.[3]
Last updated: 2/22/2012

¿Cuál es la causa del síndrome de Smith-Magenis?

El síndrome de Smith-Magenis es una cromosomopatía consistente en la delección del brazo corto del cromosoma 17.[4]
Last updated: 2/22/2012

¿Cuáles son las señales y síntomas del síndrome de Smith-Magenis?

Las señales y síntomas son variados y pueden incluir: [5]
  • Incapacidad intelectual leve o moderada
  • Atraso del habla y del lenguaje
  • Problemas de comportamiento
  • Rostro característico y más evidente con la edad, que incluye un rostro alargado y aplanado,  ojos profundos, mejillas salientes y mandíbula prominente.
  • Labios inclinados para abajo con labio superior encorvado.
  • Anomalías dentarias.
  • Disturbios del sueño
  • Problemas de comportamiento que pueden incluir agresividad, falta de concentración, impulsividad, ansiedad, auto agresividad, comportamientos repetitivos (como hacer movimientos con los dedos o ruidos con los labios) y característicamente “abrazarse a sí mismos” repetitivamente.
  • Baja estatura
  • Problemas en la columna
  • Baja sensibilidad para el dolor o temperatura
  • Problemas en los oídos y sordera
  • Problemas en los ojos como miopía
  • Defectos en el corazón
  • Defectos en el riñón
Last updated: 5/21/2012

¿Cómo puede ser tratado el síndrome de Smith-Magenis?

Su médico podrá indicarle el mejor tratamiento o hacerle una remisión para el profesional indicado. Muchos pacientes refieren mejora con el uso de medicaciones psicotrópicas para estabilizar los cambios del humor, disminuir la ansiedad, aumentar la atención y disminuir la hiperactividad.  El paciente con síndrome de Smith-Magenis debe ser visto por un equipo multidisciplinar incluyendo un médico genetista, un neurólogo y otros profesionales indicados.[4][5]
Last updated: 2/22/2012

¿Cómo es el diagnóstico del síndrome de Smith-Magenis?

El diagnóstico del síndrome de Smith-Magenis se basa en los hallazgos clínicos y es confirmado por la detección de una anomalía en el examen de los cromosomas (cariotipo) que consiste en una delección intersticial (perdida de una porción interna del cromosoma) en el segmento 17p11.2 (región 11.2 del brazo corto “p” del cromosoma 17).  Esta anomalía se puede ver en el cariotipo, en un examen llamado hibridación fluorescente in situ  (FISH) o en otro examen que se llama hibridación genómica amplia. Pruebas de genética molecular de un gen llamado RAI1,  que es el gen identificado como el responsable por el síndrome de Smith-Magenis, están clínicamente disponibles  para individuos en los que no se ha podido confirmar el diagnostico con los otros exámenes.[6]
Last updated: 2/22/2012

References
  1. Smith-Magenis syndrome. Genetics Home Reference (GHR). December 2013; http://ghr.nlm.nih.gov/condition=smithmagenissyndrome. Accessed 8/22/2014.
  2. Smith ACM et al.. Smith-Magenis Syndrome - Genetic Counseling. GeneReviews. January 7, 2010; http://www.ncbi.nlm.nih.gov/books/NBK1310/#sms.Genetic_Counseling. Accessed 2/15/2012.
  3. Smith-Magenis syndrome. Genetics Home Reference (GHR). 2007; http://ghr.nlm.nih.gov/condition=smithmagenissyndrome. Accessed 1/31/2011.
  4. Sánchez-Tatay V & González-Meneses López. Síndrome de Smith-Magenis: diagnóstico en la adolescencia. Sociedad Española de Medicina de la Adolescencia de la AEP. 2011; http://www.adolescenciasema.org/index.php?menu=documentos&id=42&id_doc=79&show=1. Accessed 1/31/2011.
  5. Smith Magenis Syndrome. Genetics Home Reference. 2007; http://ghr.nlm.nih.gov/condition/smith-magenis-syndrome. Accessed 1/31/2011.
  6. Smith ACM. Smith-Magenis Syndrome del(17)(p11.2). GeneReviews NCBI. 2010; http://www.ncbi.nlm.nih.gov/books/NBK1310/. Accessed 10/26/2011.


Other Names for this Disease
  • Chromosome 17p11.2 deletion syndrome
  • SMS
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.