As previously stated, SMS signs might be very variable, especially in later life stages. Thus, each case might show a different clinical presentation and family members of affected children should discuss the details with the medical team.

Facial features appear to be very distinctive:

• Square-shaped face
• Broad bridge of the nose
• Deep-set eyes which appear to be placed farther apart that normal (hypertelorism)
• Up-slanting palpebral fissures
• Hair growth between eyebrows to form one single long line (synophrys)
• Upper lip clearly turning downwards
• General underdevelopment of the middle portion of the face (midface retrusion)
• Disproportionately short head (brachycephaly)

The jaw might appear noticeable small (micrognathia) early in life, but as the child ages the jaw begins to abnormally protrude outward (relative prognathia) together with the general progression of all SMS signs. In addition, secondary teeth, particularly premolars, might be absent while the other teeth might display enlarged pulp chambers and reduced roots (taurodauntism). These dental signs may be accompanied by an open bite posture characterized by a considerable tongue enlargement (macroglossia) and previous episodes of teeth grinding (bruxism).

SMS signs can involve other body parts as well. Muscle tone might appear diminished (hypotonia), a condition which is frequently coupled with the presence of poor reflexes (hyporeflexia). Infants may show difficulties in growing and gaining weight at the expected rate based upon gender and age, a condition known as failure to thrive. This further complication is often worsened due to feeding difficulties such as poor sucking ability. Speech delay may also be observed in this early phase, especially as infrequent crying and diminished vocalizations characterizing the infant behavior. Affected infants may also show a general state of lethargy along with the tendency of napping for prolonged periods at daytime. The digestive system may be effected too, as indicated by the repeated appearance of gastroesophageal refluxes.

Cognitive ability is cut back to a state of mild or moderate intellectual disability in affected individuals. These are strictly connected with behavioral problems such as head banging and self-hugging which appear very early in life. Other behavioral problems can be summed up as follows:

• Hyperactivity
• Frequent tantrums
• Impulsivity
• Attention deficient disorder
• Abrupt mood changes
• Disobedience 
• Aggression
• Attention-seeking behaviors
• Toilet difficulties

Other signs of aggression might involve behaviors such as face slapping, skin picking, and hand/wrist biting which can result in self-inflicted injuries. Fingernail and toenail yanking (onychotillomania) might appear in older children, which is frequently coupled with the tendency of inserting objects into the orifices of the body (polyembolokoilamania) [7] [8] and an unusual capability of remembering faces, things, and places. It should be noted that despite the behavioral problems, affected individuals tend to show engaging personalities and a sense of humor.

Symptoms involving the ears and eyes include chronic ear infection, together with conductive hearing loss (occurring when sound wave conductivity problems arise) or increased sensitivity to particular sounds and frequencies. In regard to eye problems progressive nearsightedness (myopia), reduced cornea and crossed eyes (strabismus) are particularly frequent.

Signs might also involve larynx and its surrounding areas. Laryngeal abnormalities like polyps, nodules, and especially swelling, which results from edema, may be observed. Affected individual may experience difficulty of the mouth palate to properly close during speech (velopharyngeal insufficiency), or the problems in controlling lip, tongue, and jaw muscle movements often resulting in tongue protrusion. All these abnormalities commonly lead to vocal cord paralysis and contribute to speech delay development.

Weight gain and obesity tend to set in during adolescence, affecting 90% of children with SMS. In addition, high cholesterol levels and chronic constipation may be present. On the other hand, height seems to be seldom affected, with the majority of the patients maintaining a proper stature.

Sleep disturbances represent a life-long problem. They appear in early childhood and tend to continue in both adolescence and adulthood. Major sleep problems include difficulty in falling asleep, inability to enter into REM phase, shortening of sleep cycles, and frequent night awakening episodes. As a consequence, this might result in drowsiness during daytime associated with an inverted melatonin circadian rhythm (reported in around 90% of all cases).

Skeletal malformations often involve the spine, especially lordosis (front-to-back spine curvature) and scoliosis (sideway spine curvature). These appear frequently along with hand and feet abnormalities causing walking problems. Vertebral abnormalities and forearm and elbow limitations are rare but still significant. Other signs may suggest problems with other body systems, like:

• Thyroid function abnormalities (especially hypothyroidism)
• Immune system dysfunctions
• Defects of the heart
• Cleft lip and cleft palate
• Seizure
• Malformations affecting kidneys and urinary tract

Peripheral neuropathy should be added to this list, usually underlined by the marked decrease in pain sensitivity and loss of sensation.

• Atrial Septal Defect

  Other features include cardiac defects (ventricular septal defect, atrial septal defect, aortic stenosis,... References 1. [link.springer.com]

  The most frequent CHDs are atrial septal defects, ventricular septal defects, tetralogy of Fallot, valvular abnormalities, and total anomalous pulmonary venous connection [34]. [mdpi.com]

  CHD was found in 6 patients (atrial septal defect – 2, tetralogy of Fallot – 2, ventricular septal defect – 1, persistent left superior vena cava – 1). Different rhythm abnormalities were found in 3 patients. [chromodisorder.org]

• Pediatric Disease

  In: Cognitive and Behavioral Abnormalities of Pediatric Disease, Nass RD and Frank Y, editors. Oxford University Press, New York, NY. 2010:231-243. Smith ACM, Gropman A. Smith Magenis Syndrome. In: Management of Genetic Syndromes 3rd Edition. [rarediseases.org]

• Feeding Problems in Infancy

  Patient Registry Common features include: Developmental delay/intellectual disability Hypotonia (low muscle tone) Poor gross motor and fine motor skills Feeding problems in infancy (poor suck/swallow); failure to thrive or difficulty gaining weight (< [prisms.org]

• Pansystolic Murmur

  He has Grade III/VI pansystolic murmur best heard over the left parasternal edge and bilateral undescended testicles. Neurological examination was unremarkable except for depressed deep tendon reflexes. [annsaudimed.net]

• Prognathism

  Radiographic findings suggest the prognathic appearance is not caused by excessive mandibular growth. [ncbi.nlm.nih.gov]

  […] physical, developmental and behavioural features.2 The facial appearance is characterized by broad, square shape, brachycephaly, prominent forehead, synophrys, up-slanting palpebral fissures, deep-set eyes, broad nasal bridge, midfacial hypoplasia and prognathism [cmaj.ca]

  For example, the girl at the top of the page has heavy eyebrows, a large forehead, jaw prognathism, and a short philtrum (the groove below the nose). The Hispanic girl below also has heavy eyebrows and a short philtrum. [forgottendiseases.org]

• Onychotillomania

  A striking neurobehavioral pattern of stereotypies, hyperactivity, polyembolokoilamania, onychotillomania, maladaptive and self-injurious and aggressive behavior is observed with increasing age. [ncbi.nlm.nih.gov]

  Behavioral issues may include frequent outbursts, attention deficit/hyperactivity disorders, self-injuries with onychotillomania and polyembolokoilamania (insertion of objects into bodily orifices), etc. [kns.cnki.net]

  Older children and adults with SMS often pick at their fingers and/ or toenails until they bleed, sometimes removing the nail completely; this behavior, called onychotillomania, is unusual even among people with dual diagnosis. [thenadd.org]

• Hearing Problem

  Heart problems may require surgery to help the heart work properly. Kidney problems may also require surgery to help with bladder and kidney problems. Treatment for vision problems and hearing problems may be needed. [thinkgenetic.com]

  Some of these include: • Developmental delay • Intellectual disability • Low muscle tone • Poor gross and fine motor skills • Feeding difficulties in infancy • Vision and hearing problems • Sleep disturbance • Behavioural difficulties For children with [exerciseright.com.au]

  These include: Missing permanent teeth Taurdautism (large teeth with smaller roots) Macroglossia (large tongue) Bruxism (teeth grinding) Common physical symptoms include: Repeated ear and sinus infections Hearing problems Eye problems, such as being near-sighted [webmd.com]

• Low Set Ears

  Patient B, however, had depressed deep tendon reflexes suggestive of peripheral neuropathy.1 Common but less consistent physical abnormalities include prominent forehead, synophrys, prognathism, and low set ears. [annsaudimed.net]

  Craniofacial and skeletal abnormalities are common, including brachycephaly, broad nasal bridge, flat midface, tented upper lip, synophrys, hypertelorism, abnormally shaped or low-set ears, and brachydactyly. [link.springer.com]

• Broad Nasal Bridge

  The common clinical findings were: speech delay with behavioural problems associated with broad flat midface, brachycephaly, broad nasal bridge and brachydactyly. [ncbi.nlm.nih.gov]

  square shape, brachycephaly, prominent forehead, synophrys, up-slanting palpebral fissures, deep-set eyes, broad nasal bridge, midfacial hypoplasia and prognathism. [cmaj.ca]

  Clinical aspects All patients have a characteristic facial appearance (brachycephaly, midface hypoplasia, prominent forehead, broad nasal bridge) and a degree of mental retardation. [accessanesthesiology.mhmedical.com]

• Head Banging

  "From the time he was about 1, he was a head-banger and had very bad vision," Frey said. When he was 8, his head-banging was severe enough to cause significant damage. [abcnews.go.com]

  Severe behavior problems (biting and head banging) and sleep disturbances. Synonym SMS. Incidence Incidence estimated to be 1:25,000 live births, more than 100 patients described. [accessanesthesiology.mhmedical.com]

  […] frequent ear infections, and heart defects when compared with patients with deletion, while a subset of small deletion cases with deletions spanning from TNFRSF13B to MFAP4 was less likely to exhibit brachycephaly, dental anomalies, iris abnormalities, head-banging [ncbi.nlm.nih.gov]

  Aggression and self-mutilation, head-banging and hand-biting, and sleep disorders are the most typical behaviors, causing management problems. [pediatricneurologybriefs.com]

• Polyembolokoilamania

  Second, the syndrome is associated with polyembolokoilamania, the insertion of objects into body orifices such as the rectum, vagina, urethra, nose and ear, rather than pica, in which ingestion is restricted to the oral route, as in the patient we described [cmaj.ca]

  A striking neurobehavioral pattern of stereotypies, hyperactivity, polyembolokoilamania, onychotillomania, maladaptive and self-injurious and aggressive behavior is observed with increasing age. [ncbi.nlm.nih.gov]

  Behavioral issues may include frequent outbursts, attention deficit/hyperactivity disorders, self-injuries with onychotillomania and polyembolokoilamania (insertion of objects into bodily orifices), etc. [kns.cnki.net]

• Self-Mutilation

  Behavioural abnormalities include hypermotility, self-mutilation and sleep disturbance. [ncbi.nlm.nih.gov]

  Aggression and self-mutilation, head-banging and hand-biting, and sleep disorders are the most typical behaviors, causing management problems. [pediatricneurologybriefs.com]

  Deliberate self-harm Self mutilation [ more ] 0000742 Short nose Decreased length of nose Shortened nose [ more ] 0003196 Short palm 0004279 Short philtrum 0000322 Short stature Decreased body height Small stature [ more ] 0004322 Strabismus Cross-eyed [rarediseases.info.nih.gov]

• Wrist Biting

  biting which can result in self-inflicted injuries. [symptoma.com]

  In addition to head banging, affected children may develop other self-injurious behavior such as hand biting, face slapping, skin picking, and wrist biting. [rarediseases.org]

  During early childhood, head banging and hand or wrist biting are very common, as they are among children with mental retardation in general. [thenadd.org]

• Psychomotor Retardation

  A 3-year-old girl was referred for evaluation of moderate psychomotor retardation and several behavioral problems including self-injuring behavior, hyperactivity, and sleep disturbance. [ncbi.nlm.nih.gov]

• Hyperactivity

  […] confirm previous findings and identify new genotype-phenotype associations including differences in the frequency of short stature, hearing loss, ear infections, obesity, overeating, heart defects, self-injury, self-hugging, dry skin, seizures, and hyperactivity [ncbi.nlm.nih.gov]

  These results suggest that β 1 -adrenergic antagonists help to manage hyperactivity, enhance cognitive performance, and reduce sleep disorders in SMS. [jmg.bmj.com]

• Behavior Problem

  Smith-Magenis syndrome (SMS) is a rare syndrome with multiple congenital malformations, including development and mental retardation, behavioral problems and a distinct facial appearance. [ncbi.nlm.nih.gov]

  The major features of this condition include mild to moderate mental retardation, distinctive facial features, sleep disturbances, and behavioral problems. Smith-Magenis syndrome affects an estimated 1 in 25,000 individuals. [wikidoc.org]

  People with Smith-Magenis syndrome typically have affectionate, engaging personalities, but most also have behavioral problems. [medlineplus.gov]

  These are strictly connected with behavioral problems such as head banging and self-hugging which appear very early in life. [symptoma.com]

• High Pain Threshold

  The main features of the neurological profile of patients with SMS can be summarized as: marked developmental delay, hypotonia, hyporeflexia, high pain threshold, poor motor skills, abnormal limb tremor, among others (Greenberg et al., 1996; Gropman et [frontiersin.org]

SMS can be usually diagnosed by using the following techniques:

• Full physical examination 
• Detailed analysis of the patient's medical history
• Flourescence In Situ Hybridization (FISH) which is usually considered a confirmative technique
• Examination of the chromosomes and cytogenesis of the patient (this too is considered an important confirmative technique)
• Magnetic resonance imaging (MRI) or computed tomography (CT) scan, which are used to rule out the formation of mass lesions.

The main goal of SMS treatment is to treat and control symptoms as far as possible [9]. SMS treatment includes:

• Physical therapy
• Speech therapy
• Behavioral therapy
• Educative Learning Therapy
• Hearing aids

The diet plays an important role and should be based on vegetarian foods and other healthy products. Paramount is also the melatonin treatment, in the attempt of restoring the impaired circadian rhythm and avoiding aggressive behavior resulting from it. This is usually coupled with the administration of anticonvulsant and antipsychotic drugs to cope with psychological complications. All in all, SMS treatment requires the involvement of a team made up of different professionals, such as genetic counselors, psychologists, speech therapists, and molecular biologists.

If SMS is diagnosed early in life, prognosis for the affected patients is very good, especially in terms of life expectancy. With the proper treatment provided on a regular basis, SMS patients might live up to 60 or 70 years, just as a normal person would.

The etiological factor of SMS is a deletion of the chromosome number 17, in a section which includes the retinoic acid-induced (RAI1) gene. RAI1 has been reported to play a pivotal role in many functions of the body, including those of the brain. Unfortunately, the precise role of this gene and its related protein has not been fully understood yet [6], while the cause of the chromosomal alteration, which appears to be spontaneous, is still unknown. The chromosome rearrangements which lead to the 7p11.2 deletion are sporadic, and this explains the rare occurrence of this disorder.

SMS has been identified all over the world, with no significant difference among human races. The incidence of SMS is estimated to be around 1 every 25.000 births, even though the actual prevalence is slightly higher than that, with a rate of around 1 every 15.000 births. Therefore, the disorder is sporadic, and neither recurrence in a family or germinal mosaicism has been observed.

It is interesting to notice that a great part of affected individuals identified to date is aged between 5 to 10 years.

The vast majority of SMS cases (around 90%) has been associated with the previously mentioned deletion of the chromosome 17 in the p11.2 position (17p11.2 deletion). Deletion is usually caused by irregularities in the chromosome recombination due to the presence of frequently repeated elements in the region concerned. In particular, the region p11.2 of the chromosome 17 is among the most recombination-prone locations, reported to be associated with other genetic diseases such as hereditary neuropathy with liability to pressure palsies and Charcot Marie Tooth disease type 1A. In around 70% of the cases, the deletion is usually caused by an unequal meiotic crossover following nonallelic recombination between the repeated elements flanking the deleted region called SMS REPs. In the remaining 30% of the cases, instead, the deletion is due to recombination between other repeated elements such as AT-rich repeats or Alu elements. Furthermore, in around 10% of all SMS cases the disorder is due to mutations occurring in the RAI1 gene.

As SMS is a congenital disorder, no particular measure can be suggested to prevent it.

Smith-Magenis syndrome (SMS) is a complex developmental disorder which affects a series of body organs and systems. It is characterized by some major signs such as particular facial features and mild to moderate intellectual disabilities, which in turn are usually associated with impaired speech or language skills and sleep or behavior problems.

Main facial features include a broad and square-shaped face, full cheeks, deep-set eyes and a prominent lower jaw. Furthermore, the middle of the face and the bridge of the nose appear clearly flattened. Another characteristic feature presents the mouth as turned downward, forming an outward-curving upper lip, as well as dental abnormalities. In early childhood, these facial differences are usually mild, but become more distinctive in later stages of life.

An affectionate and engaging personality is characteristic in individuals with SMS. Moreover, they often display fits of temper, anxiety, aggression, and impulsiveness. Common behavioral abnormalities include episodes of self-injury (e.g. head banging, skin picking), difficulty in paying attention, compulsively licking fingers and flipping book pages (a behavior known as "lick and flip"), and repeatedly hugging oneself. Disrupted sleep patterns may frequently be observed early in life, with the affected subjects sleeping at day but experiencing problems falling asleep at night.

Other signs may be:

• Abnormal spine curvature (scoliosis and lordosis)
• Short stature
• Raucous voice
• Considerable reduction of pain and temperature sensitivity
• Vision problems (especially myopia)

Heart and kidney defects are reported less often [1] [2] [3] [4] [5].

Smith-Magenis syndrome is a rare congenital disorder associated with a significant developmental delay. The genetic causes responsible for Smith-Magenis syndrome generally result in learning and behavioral difficulties together with characteristic disturbances in the sleep pattern.

The major features of Smith-Magenis syndrome are the characteristic developmental delay and the related learning difficulties, which might rage from a moderate to a severe level. Early in life, failure to thrive is particularly frequent, which is usually associated with the distinctive low tone of muscles, the typical feeding difficulty and the frequent ear infections. Another characteristic feature is speech delay, especially in terms of difficult language comprehension and expression, which is usually more pronounced than motor difficulty.

Typical facial features present as heavy brows, up-slanting eyes, flat and wide head linked to a prominent forehead, and a broad mouth characterized by upper lips with fleshy and inverted central portion. Key features can involve other body parts, like spine (scoliosis and lordosis), kidney, the immune system, and frequent episodes of peripheral neuropathy like decreased sensitivity to pain and temperature.

Behavioral problems represent another key feature of Smith-Magenis syndrome, which especially consist of self-injuries like self-pitching, hand biting, and scratching. These are then accompanied by psychological problems like a restless mental state, aggression, hyperactivity, frequent and prolonged tantrum episodes, and in general easy distractibility, which partially explains the learning difficulties of affected individuals. Sleep disturbances are also typical and usually tend to continue in more advanced ages. Autistic-type behaviors, like unwillingness to change, repetitive questioning and a marked preoccupation for particular topics may also be commonly observed.

Despite the behavioral and psychological difficulties, the character of affected children is often described as loving and caring, with a great sense of humor and a peculiar love for the attention and the interaction of adults.

1. Adams DJ, Clark DA. Common genetic and epigenetic syndromes. Pediatr Clin North Am. 2015;62(2):411-26
2. Guérin-Moreau M, Colin E, Nguyen S, Andrieux J, de Leersnyder H, Bonneau D, Martin L. Dermatologic features of Smith-Magenis syndrome. Pediatr Dermatol. 2015;32(3):337-41.
3. Poisson A, Nicolas A, Sanlaville D, et al. Smith-Magenis syndrome is an association of behavioral and sleep/wake circadian rhythm disorders]. Arch Pediatr. 2015;22(6):638-45.
4. Mullegama SV, Alaimo JT, Chen L, Elsea SH. Phenotypic and molecular convergence of 2q23.1 deletion syndrome with other neurodevelopmental syndromes associated with autism spectrum disorder. Int J Mol Sci. 2015;16(4):7627-43
5. Garayzábal Heinze E, Osório A, Lens M, Sampaio A. Concrete and relational vocabulary: comparison between Williams and Smith-Magenis syndromes. Res Dev Disabil. 2014;35(12):3365-71.
6. Dubourg C, Bonnet-Brilhault F, Toutain A, et al. Identification of Nine New RAI1-Truncating Mutations in Smith-Magenis Syndrome Patients without 17p11.2 Deletions. Mol Syndromol. 2014;5(2):57-64
7. Gnanavel S. Smith-Magneis syndrome: behavioural phenotype mimics ADHD. BMJ Case Rep. 2014;2014.
8. Wilde L, Silva D, Oliver C. The nature of social preference and interactions in Smith-Magenis syndrome. Res Dev Disabil. 2013;34(12):4355-65.
9. Grigg-Damberger M, Ralls F. Treatment strategies for complex behavioral insomnia in children with neurodevelopmental disorders. Curr Opin Pulm Med. 2013;19(6):616-25.