Intellectual Developmental Disorder, X-Linked, Syndromic, Snyder-Robinson Type (MRXSSR)

What is Intellectual Developmental Disorder, X-Linked, Syndromic, Snyder-Robinson Type (MRXSSR)?

Intellectual Developmental Disorder, X-Linked, Syndromic, Snyder-Robinson Type is a rare genetic syndrome marked by intellectual disability and developmental delay. The symptoms progress from mild developmental delay to more severe intellectual disability. The syndrome also leads to muscle and bone anomalies. The syndrome affects males only and currently affects only around 10 families worldwide.

This syndrome is also known as:
Snyder-Robinson Mental Retardation Syndrome; SRS Snyder-Robinson syndrome; Spermine Synthase Deficiency; Mental Retardation, X-Linked, Syndromic, Snyder-Robinson Type

What gene changes cause Intellectual Developmental Disorder, X-Linked, Syndromic, Snyder-Robinson Type (MRXSSR)?

Changes in the SMS gene are responsible for causing the syndrome.

The syndrome is inherited in an X-linked recessive pattern, and this mode of inheritance makes it present in males almost exclusively.

What are the main symptoms of Intellectual Developmental Disorder, X-Linked, Syndromic, Snyder-Robinson Type (MRXSSR)?

The main symptoms of the syndrome include intellectual disability and delayed development which get progressively worse with age. This delay includes speech and language development with speech difficulties. In some individuals, this means the lack of any speech at all.

  • Low and thin muscle mass is common with the syndrome. As is a thin and long body with low muscle tone. Muscle tone continues to be lost with age. This in turn can create issues with walking and the development of an unsteady gait. A short stature is also a common physical feature of the syndrome.
  • Skeletal issues are also common with the syndrome. These include a thinning of the bones (osteoporosis) leading to brittle bones that break easily even without significant trauma or impact. Kyphoscoliosis- a curving of the spine is also common.
  • Unique facial features of the syndrome include a prominent lower lip, narrow roof of the mouth, cleft palate, and facial asymmetry.

Possible clinical traits/features:
Decreased muscle mass, Dental crowding, Cryptorchidism, Facial asymmetry, Dysarthria, High, narrow palate, Hyperextensibility of the finger joints, Hypertelorism, Nasal speech, Short stature, Tall stature, Mandibular prognathia, Pectus excavatum, Muscular hypotonia, Kyphoscoliosis, Intellectual disability, Long fingers, Long hallux, Long palm, Narrow palm, Wide intermamillary distance, Phenotypic variability, Recurrent fractures, Thick lower lip vermilion, Short philtrum, High myopia, X-linked recessive inheritance, Talipes equinovarus, Bifid uvula, Abnormality of the pinna, Broad-based gait, Cleft palate, Osteoporosis, Pectus carinatum, Seizure, Webbed neck.

How is it diagnosed?

To find out if someone has a diagnosis of Intellectual Developmental Disorder, X-Linked, Syndromic, Snyder-Robinson Type (MRXSSR), it is important to have a consultation and evaluation with a clinical genetic specialist.  Specialists may also suggest specific genetic testing or other types of tests to help reach a diagnosis.  FDNA’s AI technology can help speed up the diagnostic process by analyzing facial features and other health information.

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