Deleted ring chromosome 22 in a mentally retarded boy

Ring chromosome 22: a review of the literature and first report from India

Ring chromosome 22 [r(22)], a rare cytogenetic finding, has been described in nearly 70 cases to date. Cytogenetic investigations were carried out on a 5-year-old male child with microcephaly and intellectual disability. Cytogenetic investigations revealed his karyotype to be 46,XY,r(22). To the best of our knowledge, this is the first report of an r(22) anomaly from India.

Genomic designation: how genetics can delineate new, phenotypically diffuse medical categories

This paper reports and discusses 'genomic designation' as a way of classifying people. In genomic designation the object of biomedical analysis--and the concomitant medical category that is subject to scientific, clinical, and social action--is delineated on a genomic basis, while the phenotype is decentralized and tabulated post factum. Unlike prominent sociological concepts such as biosociality or geneticization, where genetic proclivities for or explanations of phenotypic categories affect social processes, genomic designation treats characteristics of the genome as the essential referent of new categories of illness. I outline the relevant sociological literature and the shift to what Nikolas Rose has called the 'molecular gaze' before explicating the concept ofgenomic designation and its half-century history. I use 22q13 Deletion/Phelan-McDermid syndrome as an example of genomic designation: investigations into the deletion of genetic material at site q13 on the 22nd chromosome preceded and made practicable the delineation of a syndrome more than a decade later, even though the associated phenotype is not distinct enough for diagnosis. Finally, I discuss the implications of this turn to 'rigidly designate' kinds of people according to observations made at the level of the genome and outline directions for future research.

Prenatal diagnosis of mosaicism for a del(22)(q13)

A case of prenatally detected mosaicism for a del(22)(q13) is reported. CVS was performed because of abnormal fetal ultrasound findings: cystic 'tumour' in the fetal neck and the upper thoracic aperture. Karyotypes from chorionic villi were suspicious of an aberration concerning the long arm of one chromosome 22. FISH analysis demonstrated mosaicism for a distal 22q deletion in fetal fibroblasts. The deletion was postnatally confirmed by FISH with a chromosome-specific 22q probe. The 'tumour' on autopsy turned out to be cystic thymic tissue. Apart from this, no other obvious fetal anomalies were found.

Metachromatic leucodystrophy (MLD) in a patient with a constitutional ring chromosome 22

Metachromatic leucodystrophy (MLD) is an autosomal recessive lysosomal storage disease resulting from a severe deficiency of arylsulphatase A. The arylsulphatase A gene is located on chromosome 22 at q13.3. An MLD patient is described who carries a common splicing mutation (“I” allele) and a de novo ring 22 deleted for the arylsulphatase A gene. The fatehr was determined to be a heterozygous carrier of the “I” allele and the mother a heterozygous carrier of the arylsulphatase A pseudodeficiency allele. The ring 22 was shown by Southern blotting to be deleted in one copy of the arylsulphatase A gene. Minisatellite analysis showed the extent of the deletion and confirmed the biparental inheritance of chromosome 22 sequences. The carrier status of the parents and the patient's 46,XX,r(22) karyotype complicated the initial diagnosis in this family. However, the causal relationship of the ring 22 and MLD have implications for the recurrence risk in this family.

Cytogenetic, biochemical, and molecular analyses of a 22q13 deletion

We report on a 3-year-old boy with a terminal deletion of 22q. The activity of alpha-N-acetylgalactosaminidase was normal while arylsulfatase A activity was reduced. Molecular analysis demonstrated the lack of paternal alleles of D22S45 and D22S55.

Terminal 22q deletion associated with a partial deficiency of arylsulphatase A

A 7 month old girl with psychomotor retardation, hypotonia, and minor malformations was found to have a terminal deletion of the long arm of chromosome 22, del(22)(q13.31). The partial deficiency of arylsulphatase A (ARSA) and the normal level of NADH diaphorase 1 (DIA1) suggests that the ARSA locus can be regionally assigned to 22q13.31----qter and the DIA1 locus can be excluded from the same segment. This report is the third published case with a terminal 22q deletion.

Partial monosomy for chromosome 22 in a patient with del(22)(pter----q13.1::q13.33----qter)

An 18 month old girl with partial monosomy for the long arm of chromosome 22 is described. The karyotype was 46,XX,del(22)(pter----q13.1::q13.33----qter). To our knowledge this is the first report of monosomy for this specific segment of chromosome 22. Clinical features include developmental delay in all areas, hypotonia, macrosomia, full cheeks, eyebrows, and eyelids, mild epicanthus, wide nasal bridge, long philtrum, and thick lower lip. Parental chromosome studies were normal.

Multiple congenital anomaly/mental retardation (MCA/MR) syndrome with Goldenhar complex due to a terminal del(22q)

We present a case of terminal del(22q) with Goldenhar complex including hemifacial microsomia, bilateral epibulbar dermoids, preauricular tags with sensorineural hearing loss, vertebral anomalies, and CNS and renal malformations. The case illustrates causal heterogeneity of the Goldenhar complex and a previously unreported associated chromosome deletion.