Comparative study of narrow band UVB versus oral acyclovir in the treatment of pityriasis rosea

Abstract

Pityriasis Rosea (PR) is a common acute self limited skin eruption with a distinctive and constant course. The initial lesion is a primary plaque that is followed after 1 or 2 weeks by a generalized secondary rash with a typical distribution lasting for about 6 weeks. The prevalence of this disorder 0.13 percent in males and 0.14 percent in females, most patients being in the age group of 10 to 43 years. The incidence at different dermatologic centers has varied between 0.3 and 3 percent. The exact etiology of the disease is uncertain, but various hypotheses have been postulated; incriminating infective agents such as viruses, fungi, streptococci and spirochetes and non infective etiologies such as atopy and autoimmune causes have also been investigated. It has been shown that PR may be associated with the reactivation of human herpes virus 7 (HHV-7) and sometimes human herpes virus 6 (HHV-6). In 80 % of cases of PR the eruption of the disease follows a distinctive and remarkably constant pattern and course. It manifests initially with a herald patch, followed by the development of a generalized secondary eruption. In about 20% of patients with PR, the clinical picture diverges from the classical one; being atypical in the morphology, or distribution and or in its course. Several atypical morphologic presentations of the solitary element of the secondary eruption of PR occur including: macular, papular, vesicular, pustular, urticarial, purpuric, lichenoid lesions, erythema multiforme-like lesions and even exfoliative dermatitis. There is no histopathologic feature pathognomonic for PR, however there are four characteristic signs which may be helpful in the differential histological diagnosis or may even permit a suspect diagnosis.Eczematoid Pattern (Unna's sign), absence or decrease of granular cell layer, erythrocytes in the papillary dermis and partly into the epidermis and homogenization of the papillary collagen. By electron microscopy, there are herpes virus-like particles in PR lesional skin. Viral particles are seen in a large numbers among the collagen fibers in the upper and middle dermis close to the blood vessels. Virions are also interspersed among keratinocytes in the vicinity of the dermal-epidermal junction. Occasionally, viral particles detected within the cytoplasm of basal keratinocytes and degenerating cells. The diagnosis of PR can usually be made on the basis of history, distribution of the skin lesions, and the individual lesion morphology. The presence of a herald patch is helpful, but may be infrequently observed. Rarely the skin biopsy is necessary. There are no laboratory studies of diagnostic importance. It is important to do serological examination for syphilis for every case of PR, especially in those not having herald patch, in order to avoid any misdiagnosis between syphilis and PR especially in sexually active individuals, also It is important to do a potassium hydroxide (KOH) preparation of skin scraping for the lesions to be examined under the