Genetic aspects of AIS

Genetic aspects of adolescent idiopathic scoliosis in a family with multiple affected members: a research article

Authors: Marcelo Wajchenberg, Monize Lazar, Natale Cava├žana, Delio Eulalio Martins, Luciana Licinio, Eduardo Barros Puertas, Elcio Landim, Mayana Zatz and Akira Ishida

Background
The etiology of idiopathic scoliosis remains unknown and different factors have been suggested as causal. Hereditary factors can also determine the etiology of the disease; however, the pattern of inheritance remains unknown. Autosomal dominant, X-linked and multifactorial patterns of inheritances have been reported. Other studies have suggested possible chromosome regions related to the etiology of idiopathic scoliosis. We report the genetic aspects of and investigate chromosome regions for adolescent idiopathic scoliosis in a Brazilian family.

Methods
Evaluation of 57 family members, distributed over 4 generations of a Brazilian family, with 9 carriers of adolescent idiopathic scoliosis. The proband presented a scoliotic curve of 75 degrees, as determined by the Cobb method. Genomic DNA from family members was genotyped.

Results
Locating a chromosome region linked to adolescent idiopathic scoliosis was not possible in the family studied.

Conclusion
While it was not possible to determine a chromosome region responsible for adolescent idiopathic scoliosis by investigation of genetic linkage using microsatellites markers during analysis of four generations of a Brazilian family with multiple affected members, analysis including other types of genomic variations, like single nucleotide polymorphisms (SNPs) could contribute to the continuity of this study.

Background
Idiopathic scoliosis is a structural lateral curvature of the spine with a rotatory component deviation in an otherwise healthy individual. These individuals present no known neurological, muscular disorders or other diseases [1] Radiography exam shows no vertebral alterations, while present with curves of more than 10°, as determined by the Cobb method [1]. Idiopathic scoliosis is one of the most frequent deformity involving the spine, with reports of its incidence in populations worldwide from 0.5% to 10%. Scoliosis progresses during the growth phase and can be classified into three categories according to the age at which the deformity is detected: infant, prior to three years of age; juvenile, between three and 10 years-old (or at the onset of puberty); and adolescent, when it appears after 10 years of age or after the onset of puberty [2].

Lonstein (1994) reported that the prevalence of idiopathic scoliosis in radiographic studies in school populations varied between 0.3 and 15.3%; however, considering only curves greater than 10°, the rates decreased to values between 1.5 and 3%. In curves greater than 20°, prevalence occurred between 0.3 and 0.5% and in curves greater than 30° the rate was between 0.2 and 0.3% [2].

The pathogenesis of idiopathic scoliosis remains unknown and different factors have been suggested as causal. Among these, the following should be highlighted: deviation from the standard growth pattern, neuromuscular or conjunctive tissue alterations, asymmetric growth of the limbs and trunk, alterations in the sagittal configuration of the spine; and environmental factors [2-5].

Hereditary factors can also determine the etiology of the disease; however, the pattern of inheritance remains unknown. Autosomal dominant, X-linked and multifactorial patterns of inheritances have been reported [1-3,5-8]. Segregation analysis has suggested a single gene as major determinant of idiopathic scoliosis in patients with curves equal to or greater than 11° (Axenovich et al. 1999). Other studies have suggested possible chromosome regions related to the etiology of idiopathic scoliosis, including a genetic locus for adolescent idiopathic scoliosis linked to chromosome 19p13.3., considering affected members as those individuals with curves greater than 10°, without reference to the presence of consanguinity [1,3,7-9].

The objective of this study is to determine a specific chromosome region related to idiopathic scoliosis in a family with multiple affected members and a high rate of consanguinity in a small town in the outback of the State of Paraiba, northeastern Brazil.

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