Acrocallosal syndrome: Description, Causes and Risk Factors:
Acrocallosal syndrome is a rare autosomal recessive genetic disorder with hypoplasia (underdevelopment of an organ because of a decrease in the number of cells) / agenesis (imperfect development; nondevelopment of a part) of corpus callosum, moderate-to-severe mental retardation, characteristic craniofacial abnormalities, distinctive digital malformations and growth retardation.
ACS is also known by its synonyms: Schinzel Acrocallosal syndrome and Hallux duplication, Post axial polydactyly and absence of corpus callosum. The inheritance is autosomal recessive based on the reports of recurrences in families and parental consanguinity. The gene responsible for this disease has not yet been identified, although Pfeiffer suggested that the gene for ACS may be situated on chromosome 12p. Linkage studies suggest that this disorder is not allelic to Greig Syndrome, despite the similarity in facial appearance and the pattern of polysyndactyly.
The acrocallosal syndrome (ACS) was first reported by Schinzel in a 4-year-old boy with post axial polydactyly, hallux duplication, absence of corpus callosum, macrocephaly and mental retardation in 1979. The name acrocallosal syndrome was proposed by Schinzel and Schimid in 1980. Since Schinzels original description, ACS has been described in over 37 cases till date.
The cause of acrocallosal syndrome is unknown. There are sporadic, or random, cases, and reports of multiple cases within families. Studies involving affected families have suggested an autosomal recessive pattern of inheritance. This means that both parents carry the altered form of the gene, and the affected child inherited both copies. Following this pattern, each child born will have a 25% risk of being affected.
To help determine which chromosome or gene location causes the syndrome, acrocallosal syndrome has been compared with similar disorders. One condition that presents similar symptoms and has a known genetic cause is Greig cephalopolysyndactyly syndrome. However, there is no genetic similarity between the two conditions. To date, no specific genetic cause for acrocallosal syndrome is known, and the disorder can only be identified by clinical symptoms.
Generalized growth retardation.
- Neurologic Signs: border line mental retardation, strabismus, hypotonia.
- Craniofacial abnormalities: Macrocephaly with dolichocephaly, frontal bossing, hypertelorism, down slanting palpebral fissure, posteriorly angulated malformed ears, short philtrum, small nose, with broad nasal bridge.
- Limb abnormalities: Long tapered fingers, postaxial polydactyly of hands, syndactyly of second and third toes, fifth finger clinodactyly, hallux valgus.
- Triple hair whorl.
- Prominent occiput.
- Deep-set eyes.
The differential diagnosis ACS includes Greig's Cephalopolysyndactyly syndrome, Oro-facial-digital syndromes Type I and II, Meckel-Gruber syndrome, Smith-Lemli-optiz syndrome, Rubinstein-Taybi syndrome.
Antenatal diagnosis is possible for better prevention of this genetic disorder. Acrocallosal syndrome should be suspected in any child with polysyndactyly, absence of corpus Callosum, mental retardation and hypotonia.
Total or partial absence of the corpus callosum. Minor craniofacial anomalies (prominent forehead, hypertelorism, short nose with anteverted nostrils and large anterior fontanels); Moderate to severe psychomotor retardation (with hypotonic); Polydactyl.
Management of ACS includes surgical correction of polydactyly, cleft palate, hernia, brain cyst/tumors and congenital cardiac malformations. Genetic counseling is of prime importance and antenatal diagnosis can be attempted by mutation analysis and antenatal ultrasound. The dental treatment planned for this patient was oral prophylaxis and extraction of over retained deciduous teeth along with root stumps followed by restoration of carious teeth.
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DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.