O. Frota-Pessoa

Waardenburg Syndrome: Clinical Differentiation Between Types I and II

Here we present the results of a study performed on 59 patients affected by Waardenburg syndrome (WS), 30 with the I variant, 21 having the type II, and 8 of them being isolated cases without telecanthus. These patients belong to 37 families; the main contributions and conclusions are based on the detailed study of 25 of these families, examined using standard procedures. All patients were examined as to the presence of eight cardinal signs important for the diagnosis of the condition; from each patient, from many of his/her normal relatives, and from a control sample of 300 normal individuals stratified by age and sex, 23 different craniofacial measurements were obtained. We also estimated, using our own data as well those collected from the literature, the frequencies of the cardinal signs, based on a total sample of 461 affected individuals with WSI and 121 with WSII. In order to originate discriminant functions to separate individuals affected by one of the two variants, both metric (from craniofacial measurements) as well as categoric data (based on the frequencies of the cardinal signs or symptoms) were used. Discriminant analysis based on the frequency of the eight cardinal signs can improve the separation of WSI patients without telecanthus from those presenting the variant II. We present also a Table with the conditional probabilities favoring the diagnosis of WSI for suspect subjects without telecanthus and any combination of the other seven signs/symptoms. The discriminant function based on the four ocular measurements (inner and outer intercanthal, interpupillary, and inferior lacrymal distances), on the other side, perfectly classifies patients affected by one of the variants of WS, the same taking place when the average values of the W index of all affected individuals per family are used. The discriminant function based solely in the individual W index values of patients correctly classifies 93% of WSII subjects, but only 60% of the patients with the I variant of WS.

New linkage data for the X-linked types of muscular dystrophy and G6PD variants, colour blindness, and Xg blood groups

Six families in which Duchenne muscular dystrophy (DMD) and G6PD or deutan colour blindness are segregating are reported. The sum of the lod-scores of these families together with three published previously indicates that the DMD locus is far from the G6PD:deutan cluster. The lod-scores of two families with Becker muscular dystrophy (BMD) informative for the G6PD locus together with those of one family previously studied by Emery, Smith, and Sanger (1969) suggest that the BMD locus could be at a measurable distance from this cluster. The maximum likelihood estimate of the recombination fraction is 0·27 and the 90% confidence limits are 0·17 and 0·40. This difference in linkage estimates for DMD and BMD suggests that the BMD and the DMD genes are located at two different loci on the X chromosome. Five more families with DMD and two with BMD informative for Xg blood groups support the conclusion of other authors that there is no hint of linkage between the loci for Xg and for the X-linked forms of muscular dystrophy.

H-Y antigen in Swyer syndrome and the genetics of XY gonadal dysgenesis

SummaryThe H-Y antigen is a plasma membrane antigen involved in the organogenesis of the mammalian testis. Its expression on human cells is determined by a Y-linked gene. Phenotypic females affected by 46,XY gonadal dysgenesis (Swyers syndrome) can be either H-Y-positive or H-Y-negative. In this paper we report H-Y antigen and endocrine studies in a sibship with three affected sisters. Immunological studies were performed on two of the patients, and a clearly positive expression was detected in both cases. Endocrine studies consisted in the investigation of the hypothalamic-pituitary-gonadal axis, which revealed that gonadal hormone insufficiency is the only endocrine abnormality associated with the syndrome. A new genetic interpretation and classification of XY gonadal dysgenesis is proposed.

Karyotypes of Seven Species of Brazilian Bats

SUMMARYThe chromosome complements of the seven species studied are as follows:Phyllostomus hastatus (2 n=32) has 13 pairs of metacentric or submetacentric and one pair of acrocentric autosomes. The X is a submetacentric and the Y is minute. Phyllostomus discolor (2 n = 32) has all its autosomes metacentric or submetacentric. The X is submetacentric. Chrotopterus auritus (2 n = 28) has all its autosomes metacentric or submetacentric. The X is a me dium submetacentric and the Y is minute. Carolila perspicillata (2 n = 20, 21) has 9 pairs of metacentric or submetacentric autosomes, all distinguishable from each other. The X is submetacentric, the Y1 is a medium acrocentric and the Y2 is a small acrocentric. Artibeus lituratus (2 n = 30, 31) has all its autosomes metacentric or submetacentric. The X is a submetacentric, the Y1 is a acrocentric and the Y2 is a small acrocentric. Desmodus rotundus (2n=28) has all its autosomes metacentric or submetacentric. The X is a submetacentric and the Y is minute. Noctili...

Turner's syndrome and 46,X,i(Yq) karyotype

A patient with features of Turners syndrome is reported. In her karyotype there were 46 chromosomes including 15 chromosomes in the C group and one metacentric marker the size of a No. 16. This marker was identified through its fluorescence pattern as being an isochromosome for the long arm of the Y. This observation strongly suggests that the male determining factors are situated on the short arm of the Y chromosome.

Use of Normal Daughters’ CPK Levels in the Estimation of Heterozygosity Risks in X-Linked Muscular Dystrophies

In order to improve the estimation of heterozygosity risks for suspected carriers of X-linked muscular dystrophies, a modification is introduced in the density formula of Emery and Morton, taking into

Recurrence risks for down syndrome

SummaryThe recurrence risks for Down syndrome due to an inherited translocation are estimated from empirical data in the literature for two maternal age groups: mothers under 30 and mothers 30 and over. These risks were found to be approximately 0.3% and 0.05%, respectively. The probability for two Down syndrome sibs both having an inherited translocation was estimated as about 18.2% for the former age group and 2.7% for the latter. The relative effectiveness in preventing Down syndrome births by karyotyping affected children is discussed.

H-Y antigen expression in a case of XX true hermaphroditism.

SummaryCells from an XX true hermaphrodite expressed a reduced amount of H-Y antigen when compared with normal XY cells and with cells from his father, who had an XY/XX chromosomal constitution. His mother had a normal karyotype and was H-Y negative. The four brothers of the patient were clinically and karyotypically normal. An X-Y interchange followed by random inactivation of the X chromosome is proposed to explain the H-Y antigen titer found in the patient.

Sex Determination of the « Pseudo-XO/XX » Type in the Brazilian Lizard Polychrus Sp. (Sauria, Iguanidae)

SUMMARYThe karyotype of the Brazilian lizard Polychrus sp showed 2n=20 chromosomes for the female and 2n=19 chromosomes for the male. The meiotic cells of the male in diakinesis and metaphase I showed 8 bivalents and 1 trivalent. In metaphase II there were cells with n=9 chromosomes, and cells with n = 10 chromosomes. The sex determining mechanism was interpreted as belonging to the « pseudo XO/XX » type, which differs from the X1X2Y/X1X1X2X2 type because the Y is morphologically indistinguishable from the X2 chromosome. This is the second occurrence of this case to be described in the vertebrates.

Atrichia, Abnormal EEG, Epilepsy and Mental Retardation in Two Sisters

Two daughters of a nonconsanguineous couple are described. Both present mental retardation, epileptic seizures, congenital atrichia, histologically anomalous skin and abnormal EEG pattern. From a discussion of the literature on atrichia, the forms without involvement of teeth, nails and hidrosis, among which recessive inheritance prevails, are distinguished from each other. None of them coincide with the syndrome described here.