Dermatopathology Case Challenge: Recognizing Mimics and Masqueraders

Dr. Carly Elston presents two dermatopathology cases focusing on distinguishing mimickers of skin conditions. The first case involves a 32-year-old HIV-positive woman presenting with diffuse alopecia, initially suggesting possible syphilis due to her clinical history. Biopsies indicated non-scarring alopecia with prominent inflammation, but syphilis stains yielded negative results. Further records revealed the patient had a history of neurosyphilis and fluctuating serology results, complicating the diagnosis amidst overlapping features with conditions like alopecia areata and syphilitic alopecia.



The second case features a male patient who developed striking flagellate erythema shortly after consuming raw shiitake mushrooms. The biopsy revealed a mixed cellular infiltrate reminiscent of both arthropod bites and Lymphomatoid Papulosis. However, clinical correlation confirmed the diagnosis of shiitake mushroom dermatitis due to an immunomodulatory effect from a heat-labile polysaccharide in the mushrooms. This highlights the importance of thorough clinical histories in dermatology to differentiate between conditions with similar histological features and emphasizes the potential for mushroom-related dermatitis, requiring careful patient inquiry about dietary or supplement histories.