Diagnosis and treatment of cutaneous herpes simplex virus infections.

Topical tretinoin (retinoic acid) has been recently approved by the Food and Drug Administration for the longterm correction of fine facial rhytides. Although its mechanism of action is unknown, tretinoin causes compaction of the stratum corneum and thickening of the epidermis and the dermis. This appears to be a safe and modestly effective alternative, even with long-term use. Collagen and gelatin matrix implants are filling materials used in dermal augmentation. When a filling material is injected into the dermis, it provides a matrix around which new collagen forms; this effaces wrinkles. Bovine collagen (Zyderm) implant consists of sterile, purified, reconstituted fibrillar bovine collagen. After injection, there is only a short-lived (often only a few months) abatement of fine wrinkles because the body's own mechanisms degrade the collagen implant; this necessitates periodic maintenance injections. Cross-linked bovine collagen (Zyplast) is associated with less rapid biologic degradation but still requires periodic re-treatment. About 3% of patients have allergic reactions to bovine collagen skin tests and cannot receive this form of therapy. Gelatin matrix implant (Fibrel) is activated by factors in a patient's own blood after intradermal administration. It is an absorbable gelatin powder that forms a matrix for complexing clotting factors with aminocaproic acid, a fibrinolytic inhibitor. Just before use, the material is mixed with the patient's plasma, which provides supplemental clotting factors. Ultimately the injected material is replaced by the patient's own collagen, and this elevates the soft tissue. An experimental means of tissue augmentation is autologous fat transplantation. This consists of the suctionassisted removal of fat from one part of the body, followed by injecting that fat into an area of depression in another skin site. Unfortunately, transplanted fat has a short survival, except in areas like the forehead where there is bone underneath the skin. The use of Clostridium botulinum A exotoxin to treat facial frown lines is currently being studied. Administering C botulinum toxin to the appropriate striated muscles produces reversible paralysis of the muscles that cause frown lines. Chemical peeling (chemexfoliation) consists of the application of one or more organic acids to the skin, which produces epidermal and upper dermal sloughing. Many peeling agents are available, including ot-hydroxy acids, trichloroacetic acid, and phenol. All result in varying degrees of destruction of the epidermis and portions of the dermis; the regeneration of epidermal and dermal tissues follows, with an effacement of fine facial rhytides. Phenol is the peeling agent that penetrates the deepest into the dermis. It is also quickly absorbed percutaneously. Systemic effects such as cardiac arrhythmias can occur, so full-face phenol peels require extensive preoperative evaluation and close postoperative monitoring. Trichloroacetic acid can produce superficial or deeper peels, depending on the concentration. The response to trichloroacetic acid is highly dependent on pre-peel skin preparation and the method of application. ot-Hydroxy acids such as glycolic acid reduce the cohesion of the keratinocytes at low concentrations; this results in mild desquamation and epidermolysis. At higher concentrations, they produce peeling into the dermis. The duration of the positive effects is under study. Complications of chemical peeling include pigmentary changes, prolonged erythema, infections, hypertrophic scarring, changes in skin texture, and atrophy. Dermabrasion has been used for decades for effacing shallow scars and other unwanted facial defects. It involves the use of a wire brush spun at high speeds and drawn over the surface of the skin so that the entire epidermis and upper dermis are removed. Residual portions of the skin's adnexal structures proliferate and reepithelialize the smooth-planed surface. The complications of hypertrophic scarring, pigmentary changes, loss of skin texture, and enlarged facial pores are possible problems with dermabrasion. The resurfacing carbon dioxide laser is now being extensively used to treat mild to moderate facial rhytides. As with chemical peels and dermabrasion, carbon dioxide laser surgery uses the mechanisms of epidermal and dermal regeneration and collagen and elastin remodeling. The result is a smoothing of superficial irregularities, including fine lines and wrinkles. It has been suggested that the carbon dioxide laser optimizes its clinical results by inducing collagen and elastin shrinkage through its thermal effect. The carbon dioxide laser allows for more precise depth control and is bloodless compared with dermabrasion. A new generation of carbon dioxide lasers has led to a reduction of undesirable results such as substantial thermal injury and scarring associated with conventional continuous-wave carbon dioxide lasers. Hyperpigmentation and hypertrophic scarring are possible complications of laser resurfacing.