Treated Whipple Disease With Erythema Nodosum Leprosum–Like Lesions: Cutaneous PAS-Positive Macrophages Slowly Decrease With Time and Are Associated With Lymphangiectases A Case Report

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Pathologically, Whipple disease (WD) is characterized by the accumulation of myriad macrophages parasitized by Tropheryma whipplei (TW) bacilli denoted by periodic acid–Schiff (PAS) positivity. These PAS+ macrophages are typically found in the duodenum associated with lymphangiectasia. Recently, we reported the presence of PAS+ macrophages and free TW in erythema nodosum leprosum (ENL)–like lesions and normal skin in a patient with WD who suffered from the immune reconstitution inflammatory syndrome (IRIS). We extend that report by describing the clinical and pathologic findings over 5 years of follow-up. First, the IRIS gradually diminished and abated over 18-month time. Second, at no point did WD recur, and all duodenal and skin biopsies tested by polymerase chain reaction were negative for TW DNA. Third, PAS+ macrophages were identified in 26 of 27 skin biopsies (96%) and decreased along with free TW over time. Fourth, ENL-like lesions had significantly greater numbers of PAS+ macrophages than normal skin. Moreover, normal abdominal skin (region of ENL-like lesions) had greater PAS+ counts than arm skin (not a site of IRIS). Last, lymphangiectases, a histologic sign of lymphostasis, was found in all skin biopsies. Overall, these findings implicate bacillary burden as a factor in the immune tolerance to live TW in active WD and the initiation of ENL-like nodules against dead/nonreplicative TW in treated WD. In addition, poor lymphatic drainage is likely responsible for the gradual clearance of TW from the skin and the impaired delayed-type hypersensitivity reaction (absence of activated macrophages) against TW found in WD, presumptively due to reduced/absent immune cell trafficking necessary for lymphocyte–macrophage interactions and induction of adaptive immunity.

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