Chromosome 11

Chromosome 11

11p13 monosomy usually occurs de novo and is called the wagr syndrome. The most constant anomaly is bilateral aniridia with other ocular anomalies. It is also associated with mental and growth retardation, ambiguous genitalia, nephroblastoma (wilms tumour) or gonadoblastoma. Familial aniridia is described with cryptic inversion involving breakpoints within band 11p13. 11p trisomy involving segment 11p12 to 11p14 shows no characteristic ocular anomaly nor signs of malignancy but rather a high convex forehead, frontal upsweep of hair, wide nose bridge, hypertelorism, short wide beaked nose, round chubby cheeks, cleft lip/palate, hypotonia and severe mental retardation. 11p15 duplication shows features of beckwith-wiedemann syndrome, macrosomia, dysmorphic facies, cleft palate and mild mental retardation.

11q2 trisomy nearly always results from a malsegregation of a parental translocation. The phenotype includes long prominent philtrum, retracted lower lip, microretrognathia frequently accompanied by malformations of the palate and by glossoptosis, suggestive of 1000

pierre robin syndrome, preauricular pits and flexion contracture of the limbs. Mental retardation and inner organ malformations are severe. A specific translocation (11;22) involving most frequently breakpoints 11q23 and 22q11 leads to a trisomy with a phenotype very similar to that of 11q2 trisomy. Some additional features probably due to the associated 22 trisomy are preauricular tags, anal atresia or stenosis. The prognosis is characterised by high frequency of early deaths. 11q-syndrome with deletion 11q24 shows congenital heart defects and coarse facial features. The main clinical features of a terminal deletion 11q23 include trigonocephaly, hypertelorism, micrognathia and heart defects. The critical chromosome segment appears to be within the 11q24.1 segment. Considerable growth and mental retardation are usual. The deletion occurs de novo in the majority of cases. Ring chromosome 11 is rare and the phenotype includes mental retardation, failure to thrive/small stature, microcephaly and cafe-au-lait spots.

Paracentric inversion inv(11)(q13q25) is associated with polysplenia syndrome including bilateral left sidedness sequence accompanied by complex cardiac malformations and failure of normal asymmetry in morphogenesis.

Important genes are localised on chromosome 11, include those for non-alpha globins, whose mutations are responsible for sickle cell anaemia and �-thalassaemia, insulin, ataxia telangiectasia and lactate dehydrogenase a. The locus for wilms tumour is on 11p13 and that for beckwith-wiedemann syndrome is on 11p15.5.

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