Diagnostic Challenge in Diagnosing Atypical Pityriasis Rosea: A Case Report.

INTRODUCTION: Pityriasis rosea is a self-limited inflammatory skin condition most commonly associated with systemic active viral infection, particularly human herpesvirus (HHV)-6 and HHV-7. Generally appearing as a herald patch, the rash subsequently spreads, commonly in a "Christmas tree" pattern on the back. There are atypical variants in which pityriasis rosea can present, making diagnosis challenging. This case is unique in that pityriasis rosea was misidentified, and it was only confirmed following histopathologic examination. Due to misidentification, there was an exacerbation of disease due to inappropriate treatment. CASE PRESENTATION: A forty-year-old male on allopurinol for gout presented to the emergency department for 2-week history worsening rash on his abdomen and extremities. He was advised to discontinue allopurinol and was given oral corticosteroids for a suspected drug eruption. He followed up in an outpatient clinic 3 days later because the rash had worsened. At the outpatient clinic, he was suspected to have a viral exanthem; however, punch biopsy of the skin was taken and later confirmed the diagnosis of pityriasis rosea. CONCLUSION: Atypical presentations of pityriasis rosea can make diagnosis challenging, resulting in misidentification. Histopathology of inflammatory skin conditions can be used in the instances of diagnostic uncertainty. Reporting atypical cases of pityriasis rosea can raise awareness and aid physicians in identifying uncommon manifestations of the disease, which can potentially prevent unnecessary treatment and their adverse outcomes.