P300 Secondary syphilis in patients living with and without HIV in Cali, Colombia: an immunohistochemistry study

Background The upsurge of syphilis cases is a public health threat, particularly in people living with HIV (PLWH). The aim of this case series was to describe the histological and immunohistochemical changes in skin lesions of patients with secondary syphilis (SS) by HIV status. Methods Clinical data and skin biopsies from SS patients who were consented and enrolled in Cali, Colombia between 2003 and 2018 were included in the analysis. Clinical data was extracted using a standardized form. Four-micrometer sections of paraffin embedded skin biopsies were stained with haematoxylin and eosin (H&E) or labelled with antibodies to detect CD4, CD8, CD56, CD68, CD138 or Treponema pallidum (Tp). Data from PLWH and people without HIV (PWH) were compared using the Fisher’s exact test for qualitative variables, the Student’s t test or the Wilcoxon rank-sum test for quantitative variables according to their distribution. The Kruskal-Wallis test was used to compare cellular populations according to categories of Tp burden (absent, sparse or moderate to severe). Results Of 114 subjects with SS, 28 PWH and 10 PLWH subjects had available skin biopsies. Most participants were male (65.8%), the mean age was 27 years (range 18–60). PLWH were more likely to identify themselves as mestizo (100% vs 52%, p=0.01), there were no differences in age, sex, symptoms or signs of syphilis. PLWH were more likely to have acanthosis (70% vs 32%, p=0.06) and epidermal hyperplasia (70% vs 18%, p=0.005). There were no differences in other H&E findings. PLWH had lower CD4 cells in the skin (p=0.0001), without differences in other cellular populations or Tp positivity. There were no differences in the cell counts by categories of Tp burden. Conclusions HIV infection was associated with non-specific epidermal hyperplasia and lower CD4 cell counts in the skin, but not with Tp positivity.