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Steroid sulphatase deficiency which started out as a curious placental microsomal enzyme deficiency associated with low maternal urinary oestrogen excretion and difficulties in delivery, first described only twelve years ago, has now become a generalized enzyme deficiency associated also with a common skin disease. It turns out not only to be inherited in an X-linked recessive manner, but to be part of a gene cluster which includes the Xg blood group gene and which has been precisely assigned to the distal tip of the short arm of the X-chromosome. This cluster is unique for genes on the X-chromosome in escaping X-inactivation. It remains to be unequivocally demonstrated whether steroid sulphatase is identical to arylsulphatase C or whether these are two enzymes sharing a common polypeptide chain determined by a single gene. However, Rose (1982) presents evidence that one steroid sulphatase is probably identical with arylsulphatase C. It also remains to be conclusively demonstrated whether the gene for the enzyme deficiency is also that for ichthyosis or whether they are two very closely linked genes. If the former is true the role of steroid sulphatase in the abnormal keratinization of ichthyosis is still to be elucidated. Above all the special nature of the DNA in this unique region awaits description.

Enzyme assays for phenylalanine mono-oxygenase have been performed on a variety of non-hepatic human cell types under varying conditions. The cell types studied were cultured fibroblasts, short-term lymphocyte cultures, long-term lymphoblastoid cultures, cultured amniotic fluid cells, hair roots and placental extracts. The cultured cells were assayed after growth under standard conditions and in the presence of a high concentration of substrate, a low concentration of end-product, added hydrocortisone or dexamethasone and under combinations of these conditions. In no instance was a significant enzyme activity obtained.

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bad, with variable results in between. Amputation of a digit is sometimes thought to produce a quicker return to work for the patient than replantation, but this is not borne out by published results."' The outlook in the leg is less clear. Functional results are often poor if a leg is replanted. Nevertheless, filleting may produce useful soft tissue which may be used as a vascularised free transfer for cover of the stump,'2 so avoiding unnecessary shortening and retaining a site of election for amputation.