Alternate Names: Williams–Beuren syndrome
Overview: William’s syndrome is a a rare neurodevelopmental
disorder caused by the deletion of about 26 genes in the long arm of
chromosome 7.
Phenotype/Characteristics: The condition manifests varied
characteristics and here are the usual phenotypes:
- prenatal and postnatal growth delay, short stature
- Inward bend of the small finger (clinodactyly)
- Sunken chest (pectus excavatum)
- Unusual appearance of the face (flattened nasal bridge with small upturned nose, long ridges in the skin that run from the nose to the upper lip, prominent lips with an open mouth, epicanthal folds, partially missing teeth, defective tooth enamel, or small, widely spaced teeth
- feeding problems (colic, reflux, and vomiting) and poor weight gain
- recurrent middle ear infections and/or effusions in childhood and mild-to-moderate high frequency sensorineural hearing loss is noted in most adolescents and adults.
- visual disturbances is possible (esotropia, cataracts, and hyperopia in as many as 50% of individuals)
- congenital heart disease and hypertension
- increased urinary frequency and daytime wetting is possible, renal abnormalities, hypercalcemia and hypercalciuria.
- delayed bone age, and decreased insulinlike growth factor-1 (IGF1) levels, glucose tolerance or overt diabetes mellitus may be detected in patients older than 20 years;
- early pubertal onset may be noted.
- A history of connective tissue abnormalities, such as abnormal joint mobility, hernias, and diverticula, is possible.
- mild-to-moderate mental retardation, but the range includes severe mental retardation to average intelligence.
- Impaired motor development is often apparent before age 42 months.
- Early language acquisition is delayed
- Visual-spatial problems (difficulties in handwriting, drawing, and gait apraxia)
- Interest and enthusiasm for music is almost universal in patients with Williams syndrome, but the ability to perform professionally is exceptional.
- As many as half of all children with Williams syndrome may exhibit autism spectrum social and communicative deficits.
- hyperactive, inattentive, and hypersensitive to loud sounds or certain types of sounds.
- Adults may have a high rate of emotional and behavioral problems, poor social relationships and anxiety, preoccupations and obsessions, phobias, panic attacks, and depression
- Few adults achieve complete independence with daily living
Frequency: Williams syndrome occurs in 1 per 7,500-20,000
births; most cases are sporadic. The deletion is equally prevalent in males and
females.
Diagnosis: Fluorescent
in situ hybridization (FISH) for the 7q11.23 elastin gene deletion should be
performed in patients in whom Williams syndrome is suspected, in addition to a
routine chromosomal analysis (karyotype). A deletion at 7q11.23 is noted on
FISH testing in 99% of patients. Mico-array
analysis may also be employed.
Causes: Caused by a deletion on band 7q11.23 near the elastin gene. It is believed that the
unequal meiotic crossover events that lead to interstitial deletions resulting
in unbalanced interchromosomal and, to a lesser extent, intrachromosomal
rearrangements.
Unequal crossover resulting in Williams syndrome
have typically been thought to result from an unequal overlap of sequences
flanking the region, resulting in a type of misalignment of the chromosomal
regions during a crossover even during meiosis. A familial inversion
polymorphism in the Williams syndrome region also predisposes the chromosome to
unequal crossover during meiosis.
Treatment/Recommendations/Therapies: Williams
syndrome is a complex multisystem medical condition that requires a
multidisciplinary team.
Hypercalcemia,
which is noted in approximately 15% of patients with Williams syndrome, is frequently
asymptomatic and resolves in the first few years of life but can be lifelong.
The goal of managing calcium and vitamin D levels is to monitor and achieve
levels in the normal range for age at intakes adequate for bone growth. The
need for dietary manipulation and medication to control hypercalcemia should be
frequently monitored because long-term unrestricted use of a low calcium, low
vitamin D formula has been reported to lead to rickets in a patient with
Williams syndrome.
Systemic
hypertension should be treated when identified.
- Visual problems and hearing loss should be periodically assessed.
- Patients with short stature should have a bone age assessment and be referred to an endocrinologist for assessment and management of growth hormone deficiency.
- Monitor for signs of precocious puberty and arrange referrals with an endocrinologist as necessary.
- Feeding difficulties in children are common, and referral to a gastroenterologist should be considered.
- Thyroid function and glucose tolerance testing should be part of the periodic evaluation.
- Early involvement of dentist is suggested.
- Cardiac surgery may be required to correct cardiac malformations
Parents of
children with Williams syndrome should be offered genetic counseling to review
their recurrence risks and options for prenatal diagnosis. If neither parent is
affected with Williams syndrome, the risk of having another affected child with
Williams syndrome is usually less than 1%. However, recurrences of Williams
syndrome have been reported, even with unaffected parents, because of apparent
germline mosaicism.
Support Groups:
William’s Syndrome Association
Williams
Syndrome Support Group -
DailyStrength
References:
Khan, A. (2012). William’s syndrome.
Retrieved March 12, 2013 from the URL: http://emedicine.medscape.com/article/893149-overview
Genetic Science Learning Center (2012, August
6) Williams Syndrome. Learn.Genetics.
Retrieved March 12, 2013, from http://learn.genetics.utah.edu/content/disorders/whataregd/williams/
Pub Med Health. (2011). William’s syndrome. Pub
Med Retrieved March 12, 2013 from the URL: http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002105/
Photo from:
http://25.media.tumblr.com/tumblr_lzrwoaVEio1r8lbh5o1_1280.jpg
Photo from:
http://25.media.tumblr.com/tumblr_lzrwoaVEio1r8lbh5o1_1280.jpg
Walang komento:
Mag-post ng isang Komento