Walker-Warburg Syndrome - Description, Causes, and Risk Factors
Walker-Warburg syndrome (abbreviation is WWS) is a type of congenital muscular dystrophy characterized by brain and eye abnormalities and muscle disease, particularly weakness and atrophy of voluntary muscles. Mutations in different genes lead to different forms of WWS, and the forms vary in regard to muscles involved, ages of onset, and severity. The overall incidence is unknown. A survey in northeastern Italy has reported an incidence rate of 1.2 per 100,000 live births. WWS is an autosomal recessive disorder. In families with one affected child, the risk of having another child with the disease is 25%.
Several genes have been implicated in the etiology of Walker-Warburg syndrome, and others are as yet unknown. Several mutations were found in the protein O-Mannosyltransferase POMT1 and POMT2 genes, and one mutation was found in each of the fukutin and fukutin-related protein genes.
There are no known candidate genes for 80%-90% of children with WWS. Although the POMT1 gene involved in WWS implies a defect in O-mannosylation of ?-dystroglycan, the exact pathophysiology of this disorder is not fully understood. As new genetic defects associated with WWS are reported, a better genotype-phenotype correlation should be established.
This congenital syndrome is considered the severest form of muscular dystrophy, with most affected children dying before the age of three.
WWS is associated with generalised hypotonia, muscle weakness, developmental delay with mental retardation and, in some children, seizures. There may be a variety of anterior eye anomalies(cataracts, shallow anterior chamber, microcornea and microphthalmia, and lens defects) and a spectrum of posterior eye anomalies (retinal detachment or dysplasia,hypoplasia or atrophy of the optic nerve and macula and coloboma). Glaucoma or buphthalmos may be present.Brain abnormalities include migrational defect with typeII lissencephaly (cobblestone type), hydrocephalus, vermal or general cerebellar hypoplasia and flat brainstem with small pyramids. White matter shows hypomyelination. Additional brain anomalies such as hypoplasia/agenesis of corpus callosum, occipital encephalocele, and Dandy-Walker malformation have been described. Other recognized associated anomalies are small penis, undescended testes, and, rarely, other facial dysmorphic features such as low-set or prominent ears and cleft lip or palate.
Laboratory investigations usually show elevated creatine kinase (CK), myopathic/dystrophic muscle pathology and altered alpha-dystroglycan.
Antenatal molecular diagnosis might be possible in families with known mutations. Antenatal ultrasound can also be helpful in families in whom the molecular defect is unknown. Hydrocephalus has been detected by ultrasound as early as at 13 weeks of gestation and occipital encephalocele, not always present, has been detected at 18 weeks of gestation.
Management is only supportive and preventive. If seizures develop, they usually need to be treated with anticonvulsants. A few children require a neurosurgical procedure such as shunting of hydrocephalus or encephalocele operation. Physical therapy can be offered to facilitate development or prevent worsening of contractures although its efficacy has not been established. Feeding needs to be monitored and supplemental nasogastric or gastric tube feeding provided in some cases. Detailed eye assessment is also needed.
NOTE: The above information is for educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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