Down's syndrome in brother and sister without evident trisomy 21.

In the present report two siblings with the typical Down's phenotype but without evident full or partial 21 trisomy are described. The finding of a regular 21 trisomy in a minority of the cells in the elder patient favors the hypothesis that both present a hardly demonstrable normal/trisomy 21 mosaicism and may be examples of a constitutional familial tendency to nondisjunction in man.

Partial trisomy 17q. Karyotype: 46,XY,der(21),t(17;21)(q22;p13).

A 15-year-old deeply mentally retarded male is described with partial distal 17q trisomy (17q22 replaced by 17qter),as the result of a de novo 17q/21p translocation. Differential Ag-staining showed that the satellites of chromosome 21 were included in the translocation chromosome.

A new characteristic karyotypic anomaly in lymphoproliferative disorders.

A new characteristic chromosome anomaly t(11;14)(q14;q32?) in lymphoproliferative disorders (LPD) is described in 4 cases. The extra material was found on a "14 chromosome (14q+) and belonged to the long arm of one "11 chromosome in 3 cases and to the long arm of a "14 in the other case. These cases confirm that the distal end of chromosome 14q may function as a "receptor site," according to the hypothesis of Kaiser-McCaw et al. and also tend to indicate that chromosome "14 may not be unique in showing so-called "donor" and "receptor sites," and that other chromosomes, in casu chromosome "11, may behave similarly.

Partial trisomy of the short arm of chromosome 3 (3p25 to 3pter). A distinct clinical entity.

Two profoundly mentally retarded brothers with partial trisomy for the distal part of the short arm of chromosome 3 (3p25 to 3pter) are described. Their anomaly arose as a segregation product of a balanced t(3p-;18q+) translocation in the mother. Compared with the other cases of partial 3p trisomy reported up to now, the present patients display a similar craniofacial dysmorphism with hypertelorism, broad nasal tip, short upper lip with prominent philtrum, and a large mouth with down-turned corners. Other stigmata, such as a prominent, high forehead with frontal bossing and full cheeks, were present during childhood but progressively disappeared.

Partial monosomy of the short arm of chromosome 9: a distinct clinical entity.

A 10-year-old girl with partial deletion of the short arm of chromosome 9 is reported; karyotype: 46,XX,del(9)(p22). This syndrome results in a distinctive craniofacial dysmorphism with trigonocephaly and contrasting midfacial hypoplasia. Partial monosomy 9p was the result of a paternal de novo germinal deletion in this case.

X-linked recessively inherited non-specific mental retardation. Report of a large family.

A large kindred is described in which 22 males and 3 females show non-specific mental retardation with impaired speech. An X-linked recessive is the most likely mode of inheritance of this condition. Similar families have been described in the literature, characteristic physical abnormalities are absent and performance I.Q. tends to be higher than verbal I.Q. This possible heterogenous condition may be a major individual cause of mental deficiency in males, and may account for the excess of male retardates in the population.

Short stature, craniofacial dysmorphism and dento-skeletal abnormalities in a large kindred. A variant of K.B.G. syndrome or a new mental retardation syndrome.

A possibly new mental retardation syndrome is described in a large family. The major features of the syndrome are: short statue, craniofacial dysmorphism and dento-skeletal abnormalities. The mode of inheritance of this syndrome appears to be autosomal dominant with a variable degree of expressivity. The possible similarity to another autosomally dominant inherited mental retardation syndrome, "the K.B.G. syndrome" as described by Hermann et al. (1975), is discussed.