Postural vasoconstriction and leg ulceration in homozygous sickle cell disease

Chronic leg ulceration is a major cause of morbidity in patients with homozygous sickle cell disease; the ulcers commonly resolve on bed rest. We have therefore compared the cutaneous vascular response to dependency in three groups of eight patients with sickle cell disease (those with an active ulcer, with an ulcer scar and with no history of ulceration) and in eight subjects with normal haemoglobin and no history of leg ulceration. We monitored with a laser Doppler flowmeter, the change in red cell (erythocyte) flux induced in the skin of the leg, at two sites proximal to the malleoli, with the leg horizontal and 5 and 10 min after moving the leg to the dependent position. With the leg horizontal, mean cutaneous red cell flux was was substantially higher in normal cells of patients with sickle cell disease than in normal subjects and was higher still at the site of the ulcer scar. On dependency, red cell flux fell not only in normal subjects but also in the patients with the sickle cell disease. The fall in red cell flux in normal skin of patients with sickle cell disease was smaller than in normal subjects when considered as a percentage of the control values, but in absolute terms the falls in red cell were similar in sickle cell patients normal subjects. By contrast, the fall in red cell flux at the ulcer/scar site was greater than in normal skin from sickle cell patients. We propose that high resting perfusion is important in patients with sickle cell disease to maintain normal integrity of cutaneous tissue and that pronounced vasoconstriction on dependency hinders the healing and encourages recurrence of the leg ulcers (AU)

Glucocorticoids and the skin

Glucocorticoids are the most effective anti-inflammatory agents currently available, but a variety of adverse effects limit their clinical usefulness. This work explores further two facets of their interaction between glucocorticoids and the skin, with the aim of identifying means of reducing glucocorticoid toxicity. (a) Metabolism of glucocorticoids by skin: Human skin is active in the terminal metabolism of corticol to cortisone, but the biological implications of this process in skin are uncertain. BEcause there are technical difficulties in dealing with human skin, an animal model, the nude mouse, has been evaluated for its suitability to the study of the metabolism of corticosterone to IIB-dehydrocorticosterone (the homologous reaction in rodents of cortisol to cortisone conversion in man); a process mediated by IIB-hydroxysteroid dehydrogenase. (b) Skin vasoconstrictor response (blanching) to topical glucocorticoids: Glucocorticoids applied topically to human skin produce vasoconstriction in dermal vessels, the degree of which correlates closely with the potency and clinically efficacy of these compounds (AU)