| Abstract: | The differential diagnosis for eosinophil‐rich skin lesions often includes a drug reaction, allergic contact dermatitis and rarely, response to a helminth infection. However, many unrelated entities, such as infections, neoplasms and inflammatory dermatoses, can have a prominent eosinophilic infiltrate. Syphilis is classically associated with plasma cells, but other patterns of inflammation have been reported, including ulcerative, granulomatous and eosinophil‐rich. Classic teaching might indicate that the presence of eosinophils argues against a diagnosis of syphilis. We present four cases of secondary syphilis with increased eosinophils, ranging from 8 to >200 eosinophils per 10 high‐power fields (×400 magnification). Patient 1 had lesions on the penis and scrotum, with greater than 200 eosinophils per 10 high‐power fields. Patient 2 had lesions on the back, with 150 eosinophils per 10 high‐power fields. Patient 3 had lesions on the bilateral arms, with 8 eosinophils per 10 high‐power fields. Patient 4 had lesions involving the anus, with 17 eosinophils per 10 high‐power fields. These cases highlight that the presence of an eosinophil‐rich infiltrate on skin biopsy should not exclude syphilis from the differential diagnosis. |
