The heterogeneity of autism spectrum disorders (ASDs) confounds attempts to identify causes and pathogenesis. Identifiable endophenotypes and reliable biomarkers within ASDs would help to focus molecular research and uncover genetic causes and developmental mechanisms. We used dense surface-modelling techniques to compare the facial morphology of 72 boys with ASD and 128 first-degree relatives to that of 254 unrelated controls. Patternmatching algorithms were able to discriminate between the faces of ASD boys and those of matched controls (AUC = 0.82) and also discriminate between the faces of unaffected mothers of ASD children and matched female controls (AUC = 0.76). We detected significant facial asymmetry in boys with ASD (P < 0.01), notably depth-wise in the supra-and periorbital regions anterior to the frontal pole of the right hemisphere of the brain. Unaffected mothers of children with ASD display similar significant facial asymmetry, more exaggerated than that in matched controls (P < 0.03) and, in particular, show vertical asymmetry of the periorbital region. Unaffected fathers of children with ASD did not show facial asymmetry to a significant degree compared to controls. Two thirds of unaffected male siblings tested were classified unseen as more facially similar to unrelated boys with ASD than to unrelated controls. These unaffected male siblings and two small groups of girls with ASD and female siblings, all show overall directional asymmetry, but without achieving statistical significance in two-tailed t-tests of individual asymmetry of ASD family and matched control groups. We conclude that previously identified right dominant asymmetry of the frontal poles of boys with ASD could explain their facial asymmetry through the direct effect of brain growth. The atypical facial asymmetry of unaffected mothers of children with ASD requires further brain studies before the same explanation can be proposed. An alternative explanation, not mutually exclusive, is a simultaneous and parallel action on face and brain growth by genetic factors. Both possibilities suggest the need for coordinated face and brain studies on ASD probands and their first-degree relatives, especially on unaffected mothers, given that their unusual facial asymmetry suggests an ASD susceptibility arising from maternal genes.
Mosaicism for a balanced reciprocal translocation is uncommon. These two new cases were detected during investigation of infertility and miscarriages. Otherwise, the probands were normal. Of five previously described cases, only one was possibly syndromal. More reports of this class of chromosomal aberration are needed to assess accurately the risk of phenotypic abnormalities.
We report a case of a child with features of Down syndrome (DS) but with an atypical karyotype. Initial chromosome analysis was 46,XX,dup(21q).ish 21(wcp21+). The father's chromosomes were normal. However, the mother was found to have mosaicism for a pericentric inversion of chromosome 21 (19/30 cells). The revised chromosome result of the child was 46,XX,rec(21)dup(21q)inv(21)(p12q21.1)mat. A literature review of similar cases (hereafter referred to as rec dup(21q)) was conducted to aid counselling about recurrence risks and the prognosis for this child. All previous reports of rec dup(21q) were secondary to a maternal pericentric inversion. Male carriers did not seem to be at risk of having offspring with the rec dup(21q), although the number of male carriers was limited. In those with rec dup(21q), the risk of congenital heart disease was similar to that of trisomy 21. In reported cases, the facial appearance was suggestive of Down syndrome but perhaps less striking. Although the data are limited, there is an indication the developmental disabilities and short stature are milder in those with rec dup(21q) compared to trisomy 21. These observations promote the concept that the region of chromosome 21 proximal to the duplication contains genetic information contributing to the expression of some features of Down syndrome.
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