Hyperhomocysteinemia is an independent risk factor for vascular disease, including coronary disease, and in most instances is probably due to cystathionine beta-synthase deficiency.

SUMMARY Histological examination of the breasts of 26 infants and young children who died suddenly between the ages of 3 weeks and 2 years was performed. The glands were composed of well formed lobules surrounded by dense interlobular stroma, while within the lobules there was looser connective tissue. The lobules contained ducts, many of which were dilated and contained secretions. Foci of extramedullary haematopoiesis were found, and in the older infants, fat was prominent within the connective tissue of the breast. Myoepithelial cells were regularly present. No sex differences in breast development at this time were noted. Newborn breast development did not regress rapidly after birth and secretory activity continued for many months in both sexes. This study shows that the human mammary gland remains active for many months after birth and may continue to grow and secrete. The findings are not consistent with the current view that breast development in infancy results from stimulation from 'pregnancy hormones.' It is more likely that the infant's own gonadal secretions are responsible.The human mammary gland has a number of well recognised phases of growth and development. In late pregnancy the fetal breast (in both sexes) is highly developed, and at birth it often secretes milk. Then at puberty the growth of the breast is usually the first sign of secondary sexual development in girls, and at this time gynaecomastia is not uncommon in boys.2 The breast reaches its maximal development during pregnancy in preparation for lactation. There is, however, another ill recognised phase of development of the human mammary gland in the first year or two of life long after the influences of pregnancy have been removed.Contrary to what has been stated3 the infant's breast does not regress rapidly after birth. Careful clinical study has shown that it often persists as a firm discrete nodule in many boys and girls during the first year of life and it may be more prominent by the age of 6 months than earlier and it is only later in infancy that the first sex differences in breast size appear: the gland being bigger then in girls.1 In prematurely born infant girls this phase of development may be even more prominent.4 After the first two years the breast bud usually remains small and barely palpable until puberty.The histological appearances of the breast in the fetus, at birth, in puberty, and pregnancy have been well described,5 6 but there are few reports on breast histology in infancy after the immediate newborn period. Also it is likely that the specimens of breast tissue that were subject to histological examination were from infants who had died in hospital after chronic illnesses. To obtain information on the natural history and histological appearances of the breast in healthy children it was decided to examine the glands of previously well infants and young children who had died suddenly. Materials and methodsThe breast bud and surmounting elipse of nipple containing skin was excised from a total of 22 cases of sudd...

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