It is strange that the existence of oral psoriasis seems so rare. Other papulosquamous disorders, such as lichen planus, are frequently associated with oral manifestations, yet oral psoriasis is rare given the prevalence of cutaneous disease. One explanation is that oral lesions are asymptomatic and do not come to the clinician's attention. Other explanations, however, are necessary. Epithelial turnover time is significantly increased in psoriatic plaques and may be as rapid as 3 to 7 days, whereas normal epithelial turnover is 28 days. Some have suggested that this abnormally increased turnover time in psoriasis approximates that of the normal regenerative time of the oral epithelium, and this possibility may account for the apparent lack of changes in the oral mucosa of patients with psoriasis . It is also possible that oral lesions of psoriasis are altered both clinically and histologically by other factors within the oral microenvironment and are not recogized . Although controversy has appeared in the literature about whether lesions of oral psoriasis exist, there is sufficient evidence that a subset of patients have oral lesions in association with skin disease. This occurrence is more common in patients with the severe forms of psoriasis, such as generalized pustular psoriasis. The diagnosis of oral psoriasis should be based on good clinical and histologic evidence, and, in general, the clinical course of the oral lesions should parallel that of the skin disease. Exclusion of other causes is important, particularly if cutaneous lesions are absent and a diagnosis of isolated oral psoriasis is entertained. Because neither the clinical nor the histologic changes are absolutely specific for psoriasis, the patient requires holistic evaluation. That being said, in day-to-day practice it is most likely not practical to obtain a biopsy of asymptomatic oral lesions for definitive histologic or immunofluorescence studies. The clinician, however, must have a high degree of awareness and pay close attention to the oral mucosa in patients with psoriasis. A thorough examination is imperative, because asymptomatic oral lesions may be found more frequently in patients with psoriasis if clinicians habitually check mucous membranes during the generalized skin examination. Conversely, in patients with troublesome oral lesions, a cutaneous examination that reveals subtle changes suggestive of psoriasis may provide clues to the oral diagnosis. A detailed history remains the cornerstone of diagnosis, because a family history of psoriasis or a history of psoriasis now in remission may guide physicians when they note oral lesions.
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