Carlo Baccichetti

The “Cat Eye syndrome”: Dicentric small marker chromosome probably derived from a No. 22 (Tetrasomy 22pter→q11) associated with a characteristic phenotype

Eleven patients with the so-called Cat Eye syndrome are reported including a more detailed description of the original cases reported by Schmid and Fraccaro. All cases had, in addition to a normal karyotype, a small extra G-like chromosome which appeared to be an isochromosome for the juxtacentromeric region (pter to q11) of an acrocentric chromosome. None were mosaics. Clinical findings and further cytogenetic studies in a few cases suggest that these markers probably derive from a No. 22 chromosome. Characteristic features of the Cat Eye syndrome in these 11 patients and those reviewed from the literature are: ocular coloboma which may involve the iris, choroid and/or optic nerve, preauricular skin tags and/or pits which are probably the most consistent feature, congenital heart defect, anal atresia with a fistula, renal malformations such as unilateral absence, unilateral or bilateral hypoplasia, and cystic dysplasia, and antimongoloid position of eyes. Intelligence is usually low-normal, although moderate retardation is also seen. There is great variability in the clinical findings ranging from near normal to lethal malformations. Less frequent, but also characteristic findings are: microphthalmia, microtia with atresia of the external auditory canal, intrahepatic or extrahepatic biliary atresia and malrotation of the gut. Direct transmission of the marker from one generation to the other was observed in both sexes. In those families, there was considerable variability in the clinical findings between affected family members. These cases show that there is a bias of ascertainment for patients who have the more striking malformations, especially those with ocular coloboma and anal atresia, a combination which appears to be present in only a minority of cases. Many mildly affected patients probably remain undetected. It is proposed that the term Cat Eye syndrome should be applied only to cases with trisomy or tetrasomy of not more than 22pter to q11 and without additional duplication or deletion of another autosomal segment.SummaryEleven patients with the so-called Cat Eye syndrome are reported including a more detailed description of the original cases reported by Schnid and Fraccaro. All cases had, in addition to a normal karyotype, a small extra G-like chromosome which appeared to be an isochromosome for the juxtacentromeric region (pter→q11) of an acrocentric chromosome. None were mosaics. Clinical findings and further cytogenetic studies in a few cases suggest that these markers probably derive from a No. 22 chromosome.Characteristic features of the Cat Eye syndrome in these 11 patients and those reviewed from the literature are: ocular coloboma which may involve the iris, choroid and/or optic nerve, preauricular skin tags and/or pits which are probably the most consistent feature, congenital heart defect, anal atresia with a fistula, renal malformations such as unilateral absence, unilateral or bilateral hypoplasia, and cystic dysplasia, and antimongoloid position of eyes. Intelligence is usually low-normal, although moderate retardation is also seen. There is great variability in the clinical findings ranging from near normal to lethal malformations. Less frequent, but also characteristic findings are: microphthalmia, microtia with atresia of the external auditory canal, intrahepatic or extrahepatic biliary atresia and malrotation of the gut.Direct transmission of the marker from one generation to the other was observed in both sexes. In those families, there was considerable variability in the clinical findings between affected family members. Theses cases show that there is a bias of ascertainment for patients who have the more striking malformation, especially those with ocular coloboma and anal atresia, a combination which appears to be present in only a minority of cases. Many mildly affected patients probably remain undetected.It is proposed that the term Cat Eye syndrome should be applied only to cases with trisomy or tetrasomy of not more than 22pter→q11 and without additional duplication or deletion of another autosomal segment.

Natural course of subclinical hypothyroidism in Down’s syndrome: Prospective study results and therapeutic considerations

Pathogenesis, natural course and therapeutic management of subclinical hypothyroidism (SH) in Down’s syndrome (DS) remain object of debate in literature. In the present study thyroid function, antithyroid antibody (ATA) prevalence and serum lipid concentrations were investigated in a group of 344 Down patients (DP) and data were compared with those obtained from a control group of 257 age and sex matched healthy subjects. Thyroid function and ATA prevalence were also studied in 120 parents of DP. SH prevalence was clearly higher in DP (32.5% of cases) than in controls (1.1%) and parents (0%). Similarly, ATA prevalence was higher in DP (18% of cases) than in controls (5.8%) and parents (6.6%). In spite of this, no correlation was found in DP between SH and ATA prevalences, since ATA were detected in 18.7% of SH-DP and in 15.8% of euthyroid DP. Thus, circulating ATA were not detected in the majority of SH-DP. No significant differences regarding T4, FT4, T3 and serum lipid levels among SH and euthyroid DP and controls were found. Moreover, TSH levels were only slightly increased, generally less than 10 μU/ml, in most cases of SH-DP. Follow-up was longer than 24 months (range 2–7 years, mean 3.1) in a group of 201 DP: two different patterns of SH course were observed, mainly depending on the presence or the absence of circulating ATA. In particular, 35.7% of ATA-positive SH-DP developed a clinically evident thyroid disease (overt hypothyroidism or hyperthyroidism), while no similar case was recorded among ATA-negative SH-DP. On the contrary, a significant number of these patients (33.9% of cases) showed a spontaneous normalization of TSH levels. The present data suggest that: a) DS per se seems to be a clinical risk condition in developing thyroid autoimmune diseases, b) SH represents a very common conditions in DP and in most cases it appears to be independent of the presence of circulating ATA, c) SH alone, that is in the absence of detectable ATA, does not seem to be predisposing condition to develop a clinically evident thyroid disease, as a spontaneous normalization of TSH levels is often observed. From the therapeutic point of view, it seems unlikely that L-thyroxine substitutive therapy could lead to some improvement in SH-DP in the absence of detectable ATA. A wait and see policy with frequent thyroid function screening could be considered adequate, thus avoiding chronic hormonal therapy at least in DP in whom TSH levels tend to spontaneously normalize. On the contrary, L-thyroxine should not be delayed in ATA-positive SH-DP due to the frequent evolution towards an overt thyroid disease.

Duplication of an Xp segment that includes the ZFX locus causes sex inversion in man

SummaryTwo 46,XY females with tandem duplications of an X short arm segment were studied by cytogenetic and Southern blot analysis. The results show that the duplicated segment in each case included the Xp21.2–Xp22.2 interval, resulting in a double dose of ZFX on the single active X chromosome. The results from our two cases, in conjunction with those reported by other workers, lead us to conclude that the duplication is the reason for the sex inversion. If ZFY and ZFX are indeed sex-determining gene loci, these findings favour a model of sex determination characterized by antagonistic interaction between these genes.

A New Case of Trisomy for the Short Arm of No. 9 Chromosome

A new case with trisomy for the short arm of No. 9 chromosome, identified by heat treatment and Giemsa staining is reported. The clinical picture and dermatoglyphic patterns are similar to those previously reported.

Chorio-retinal dysplasia, microcephaly and mental retardation. An autosomal dominant syndrome.

A condition is described which is characterized by chorio‐retinal dysplasia, microcephaly and mental retardation, transmitted in an autosomal dominant fashion with variable expressivity. It is suggested that this condition is a distinct autosomal dominant syndrome.

Electroclinical diagnosis of Angelman syndrome: a study of 7 cases

The authors describe 7 new cases of Angelman syndrome (AS: 3 males and 4 females) diagnosed on the basis of clinical features (dysmorphic facial features, severe mental retardation with absent speech, peculiar jerky movements, ataxic gait and paroxysms of inappropriate laughter) and neurophysiological findings. Failure to detect deletion of the long arm of chromosome 15 or the absence of epileptic seizure were not considered sufficient to exclude a diagnosis of AS. Feeding problems, developmental delay and early signs of ataxia, especially tremor on handling objects and unstable posture when seated, proved effective as clinical markers for early diagnosis of AS. The EEG patterns characteristic of AS were found within the first 2 years of life (under 18 months in the majority of cases). The authors conclude that AS should be included in differential diagnosis in a child aged under 12 months having cryptogenic psychomotor retardation with prevalent language compromise. Repeat EEG recordings are needed to check for the typical trace, and cytogenetic investigations are mandatory.

Trisomy 4q32 leads to 4qter due to a maternal 4/21 translocation.

The case is described of a malformed girl with partial trisomy for a segment of the long arm of chromsome (4q32 leads to qter) due to an unfavourable segregation of a maternal reciprocal translocation t(4;21) (q32q22). The clinical comparison between the child and patients previously described by other authors does not suggest the existence of a syndrome associated with trisomy 4q+.

Cytogenetic findings in 4952 prenatal diagnoses. An Italian collaborative study

SummaryThe development of prenatal diagnosis in Italy was made difficult by the restrictions of the old abortion law and only in recent years has a consistent number of cases been investigated. We report the experience on prenatal chromosome diagnosis of ten Italian centers participating in a collaborative study on 4952 diagnoses performed from 1972 to 1980. The main indication groups were: advanced maternal age (2882 cases), previous child with chromosome anomaly from parents with normal karyotype (847 cases), and chromosome anomaly in one parent (97 cases). The other indications for amniocentesis, including cases without a cytogenetic risk, have been assembled into a “miscellaneous” group (1126 cases). We found 125 abnormal fetal karyotypes (2.5%) of which 89 were unbalanced (1.8%). The frequencies and types of chromosome anomalies are reported in detail for each indication group and are compared with the corresponding ones from the European Munich Conference. The great majority of these Italian data were not included in the Munich report.

Study on segregation and risk for abnormal offspring in carriers of pericentric inversion of the (p11←q13) segment of chromosome 2

Pericentric inversion of chromosome 2 was detected in four unrelated families. All these inversions involved the segment p11←q13. The pedigree data are considered in comparison with other cases reported in the literature. Segregation data and possible reproductive failures are discussed.

Study on segregation of the inversion of chromosome 4 (p15.2q11) in two unrelated families

SummaryA pericentric inversion of chromosome 4 with identical breakpoints (p15.2q11) has been found in two unrelated families. The presence of the inversion in three generations was observed but no recombinants have been recognized. In order to provide appropriate genetic counselling, segregation data and possible reproductive risk are discussed.