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A new case of partial trisomy 13 through unbalanced de novo translocation t(X;13) is reported. In situ hybridization has been used to specify breakage points on the X chromosome. This case is cytogenetically comparable with another reported case; the phenotypical aspect of these two patients is however different. This discrepancy is discussed.

Two unrelated patients with partial trisomy 10p due to a paternal balanced translocation are reported. Though the sizes of the trisomic segment are not identical, both patients show: severe growth retardation, important psychomotor retardation and a dysmorphic mouth recalling a "tortois mouth". These observations are compared to twelve others from the literature.

The frequency of retinoblastoma was estimated in southwest France (Midi-Pyrénées) during the 1950-1969 period. Twenty-three cases were detected among 507 157 liveborns. After correcting for the probability of ascertainment of patient, the estimated frequency is 1 per 15 849 births. The proportion of unilateral cases is estimated 91 percent after correcting for the higher probability of ascertaining bilateral cases.

A blastic crisis of chronic myeloid leukemia without a detectable chronic phase is reported. At diagnosis, blast cells present t(9;22)(q34;q11),t(14;14)(q11;q32) translocations and early B cell phenotype (DR +, TdT +, B4 +, BA1 +, J5 +). At relapse, the malignant clone evolves to a biphenotypic expression, the initial markers remain unchanged, and two myeloid antigens (My 7, My 9) appear. The wide overlap in percentages of blast cells displaying lymphoid and myeloid markers shows that a single clone bears antigens of both lineages. Simultaneous occurrence of a t(14;14)(q11;q32) translocation, usually found in T cell malignancies, and of a B cell phenotype raises the question of the relationship between chromosomal changes and surface marker expression. The malignant cell is assumed to be a progenitor cell, already committed to lymphoid lineage and retaining the potential to switch to myeloid lineage.

A new case of monosomy 10p without associated chromosomal abnormality is reported. This observation, compared with three others from the literature, shows the following common symptoms: microcephaly, antimongoloid slant of the palpebral fissures, low-set ears, prominent anthelix, congenital heart disease, abnormalities of the limbs. Cranial tomography demonstrates a midline developmental anomaly of the brain (cavum vergae associated with cavum septi pellucidi).