Stephen K. Tyring

Cutaneous Squamous Cell Carcinomas in Organ Transplant Recipients

Non-melanoma skin cancers represent a major cause of morbidity after organ transplantation. Squamous cell carcinomas (SCC) are the most common cutaneous malignancies seen in this population, with a 65–100 fold greater incidence in organ transplant recipients compared to the general population. In recent years, human papillomaviruses (HPV) of the beta genus have been implicated in the pathogenesis of post-transplant SCCs. The underlying mechanism of carcinogenesis has been attributed to the E6 and E7 proteins of HPV. Specific immunosuppressive medications, such as the calcineurin inhibitors and azathioprine, are associated with a higher incidence of post-transplant SCCs compared to other immunosuppressive agents. Compared to other immunosuppressives, mTOR inhibitors and mycophenolate mofetil have been associated with a decreased risk of developing post-transplant non-melanoma skin cancers. As a result, they may represent ideal immunosuppressive medications in organ transplant recipients. Treatment options for post-transplant SCCs include surgical excision, Mohs micrographic surgery, systemic retinoid therapy, adjunct topical therapy, electrodessication and curettage, and radiation therapy. This review will discuss the epidemiology, risk factors, and management options of post-transplant SCCs. In addition, the underlying mechanisms of beta-HPV mediated carcinogenesis will be discussed.

Valacyclovir for the treatment of genital herpes

Genital herpes is the most prevalent sexually transmitted infection in the USA. While sometimes mild in severity, it can be a distressing and painful chronic condition. Likewise, herpes labialis and herpes zoster can be both physically and psychologically painful. While there is no cure for these conditions, treatment to alleviate symptoms, suppress recurrences and reduce transmission has been drastically improved over the past 20 years with the use of guanine nucleoside antivirals, such as valacyclovir hydrochloride (Valtrex®, GlaxoSmithKline) the highly bioavailable prodrug of acyclovir (Zovirax®, GlaxoSmithKline), and famciclovir (Famvir®, Novartis), a highly bioavailable prodrug of penciclovir (Denavir®, Novartis). Clinical trials involving approximately 10,000 patients (including patients from nongenital herpes studies, such as herpes zoster) have assessed the safety and efficacy of valacyclovir in the treatment of initial genital herpes outbreaks, episodic treatment of recurrent episodes and daily suppressive therapy. It was shown that valacyclovir has similar efficacy to acyclovir in the episodic and suppressive treatment of genital herpes. Valacyclovir is the only antiviral drug approved for a once-daily dose of suppressive therapy for genital herpes, as well as the only antiviral drug US FDA approved for a 3-day regimen of episodic treatment of recurrent genital herpes. In addition, valacyclovir is also indicated in the reduction of the sexual transmission of herpes simplex virus infection and for the treatment of herpes labialis. In herpes zoster, valacyclovir is more effective than acyclovir or placebo (and as equally effective as famciclovir) in shortening the length and severity of herpes zoster-associated pain and postherpetic neuralgia. Valacyclovir has an acceptable safety profile in patients with herpes simplex and herpes zoster. The less frequent dosing regimen makes it an attractive option in the treatment of genital herpes and other viral infections, and may contribute to increased patient adherence to therapy.