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Frequently Asked Questions (FAQ)

What are the symptoms of MSS?

Some symptoms occur in almost all reported cases of MSS. These symptoms include cataracts (progressive loss of transparency of the eye lens),  ataxia (impaired ability to coordinate movement),  hypotonia (floppiness), short stature,  dysarthria (slow, weak, or imprecise speech due to weakness or incoordination of speech muscles), and mental retardation (generally in the mild-moderate range). Other symptoms such as hypergonadotropic hypogonadism (decreased function of the ovary/testis), nystagmus (involuntary, rhythmic movements of the eyes) and skeletal abnormalities are reported less frequently.

How is MSS inherited?

MSS is autosomal recessive. It occurs with equal frequency in males and females. If both parents are carriers, there is a 25% chance that any child will have the disorder.   In November 2005, a gene (SIL1) was identified that is responsible for about half of the known cases of MSS. 

How prevalent is MSS?

MSS is very rare. About 100-200 cases have been reported in the literature. It has been reported in numerous countries including the United States, Japan, Scandinavia, Italy, England, France, Kuwait, and others. Many reported cases are consanguinous (parents are related).

How is a child diagnosed with MSS?

In most cases, the first signs of a problem is hypotonia (floppiness). The infant does not develop good head control and does not achieve motor milestones (rolling, sitting, standing, walking) at a typical age. Generally the child is referred by the pediatrician to a pediatric neurologist, developmental pediatrician, and/or geneticist. Tests often include extensive blood and urine tests, MRI (magnetic resonance imaging), nerve conduction studies, and in some cases, skin and muscle biopsies. By the age of one, small stature usually becomes more apparent. Cataracts appear in early childhood and can develop quickly. The child generally achieves good mobility with a walker or crutches, but independent walking is unlikely due to ataxia and muscle weakness. Other signs of cognitive delay likely appear (delays in speech and language, self-help, social skills, and academic skills). 

What can I expect as my child grows older?

The medical literature reports a wide-range of scenarios for the MSS patient. The variation is probably due to a combination of individual differences, increased availability of early intervention and educational opportunities sinces the 1960s, and uncertainty in diagnosis. Most patients continue to use walkers and crutches for mobility. There are some reports of increasing weakness with age which may require use of a wheelchair. Many people live to a relatively old age (some into the 70's). Cognitive function ranges anywhere from moderate retardation to near-normal.

How tall is my child likely to get?

This chart shows how some MSS girls and boys compare to the general population.

How can I help my child with MSS?

Early intervention (including physical therapy, occupational therapy, and speech therapy) and careful selection of educational programs are critical.  Selection of a supportive team of doctors, therapists, and educators who communicate well with the family can significantly affect outcome. Learn as much as possible about the disorder and communicate with others.

What else do I need to know?

When the cataracts significantly impair vision, the child will require cataract extraction followed by insertion of intraocular lenses.  Alternatively they can wear cataract glasses or contact lenses.  Glaucoma is a potential risk in children you have had cataract surgery, particularly when the cataracts are removed in the first year of life. 

Many children with MSS wear foot/ankle orthotics (braces) to provide proper alignment and improved stability.

What other syndromes are similar to MSS?

Differential diagnosis (see medical summary) includes:

Congenital Cataract Facial Dysmorphism Neuropathy Syndrome (CCFDN)
Mucolipidosis IV
Lowe Syndrome
Congenital Disorders of Glycosylation
Zellweger Syndrome

Some children once suspected to have MSS have later been diagnosed with:
Mitochrondrial Disease

Where can I find more information about MSS and other genetic disorders?

Gene Reviews (a comprehensive summary of MSS)

PubMed (access to many medical abstracts and articles)
Gene Clinics (laboratories conducting research on MSS)
MSS Online Mendelian Inheritance in Man (OMIM)
Humane Genome Project Information