SUMMARY A patient with alpha heavy chain disease (aHCD), who showed an abnormal chromosomal marker (D14 q +) in 10 % of the bone marrow cells, is described. The mesenteric lymph nodes, which showed reactive hyperplasia in the first biopsy, transformed later to a malignant lymphoma and finally to a plasma cell tumour. The small intestine revealed villous atrophy, diminished crypts, and intact surface epithelium. The ultrastructure of the goblet and epithelial cells appeared to be normal, and the microvilli were preserved except for circumscribed areas of destruction. The lamina propria was heavily infiltrated with mononuclear cells, mainly mature plasma cells. Alpha heavy chains (xHC) were found in the patient's saliva.

Several authors have suggested that heterochromatin polymorphism influences the origin and/or development of different malformations. In this investigation special consideration was given to the Ajqh+ variant. Several families with this variant are reported in which the incidence of otherwise rare malformations is surprisingly high. The possibility that the Aiqh+ variant or, more probably, interactions between all types of heterochromatin polymorphism are of pathogenetic significance is considered.

A 26‐year‐old patient with female phenotype and the karyotype 46, x, i (Yq) is described. She had no breast, and a rudimentary uterus and streak gonads were present. Apart from a rather deep voice, no signs of masculinization were observed, nor did she display any of the stigmata usually associated with Turner's syndrome. The Yq chromosome was identified conclusively by the Giemsa C‐banding technique. The function of the Y chromosome is discussed briefly, and it is concluded that the factors determining or regulating somatic male differentiation must be located in the short arm of the Y chromosome.

Complete triploidy was found in lymphocyte cultures From a stillborn full‐term female infant with a birthweight of 1,000 g. The child had B ventricular septal detect of the heart hut no other macroscopic internal or external malformations. The mother, who had a history of prolonged anti‐asthmatic medication, displayed a high incidence of satellite associations and chromatid breakages in her cultured lymphocytes. The possibility that such changes are instrumental in the formation of triploid zygotes is discussed.

A new variant of chromosome 18 (18 Ch+ sat+) is reported. It was present in the normal mother and in her malformed child, who had a midline cleft of the face. The possibility that the variant was indirectly involved in the causation of the abnormality is discussed and, alternatively, the hemizygous expression of a recessive gene for holoprosencephaly by suppression of its normal allele.