Immunohistochemical detection of Treponema pallidum in skin samples with clinical and histopathological correlations and Warthin-Starry staining critical analysis.

BACKGROUND

Syphilis in its different phases may be a difficult diagnosis in clinical and histopathological grounds.

OBJECTIVES

The present study objectives were to evaluate the detection and tissue distribution of Treponema pallidum in skin lesions of syphilis.

METHODS

A blinded diagnostic accuracy study was performed with immunohistochemistry and Warthin-Starry silver staining in skin samples from patients with syphilis and other diseases. Patients attended two tertiary hospitals between 2000 and 2019. Prevalence ratios (PR) and 95% confidence intervals (95% CI) were calculated for the association between immunohistochemistry positivity and clinical-histopathological variables.

RESULTS

Thirty-eight patients with syphilis and their 40 biopsy specimens were included in the study. Thirty-six skin samples were used as non-syphilis controls. The Warthin-Starry technique was unable to accurately demonstrate bacteria in all samples. Immunohistochemistry showed spirochetes only in skin samples from patients with syphilis (24/40) with 60% sensitivity (95% CI 44.8‒75.2). Specificity was 100% and accuracy, 78.9% (95% CI 69.8‒88.1). Most cases had spirochetes in both dermis and epidermis and there was a high bacterial load.

STUDY LIMITATIONS

Correlation between immunohistochemistry and clinical or histopathological characteristics was observed but was limited statistically due to the small sample size.

CONCLUSIONS

Spirochetes were promptly seen in an immunohistochemistry protocol, which can contribute to the diagnosis of syphilis in skin biopsy samples. On the other hand, the Warthin-Starry technique showed to be of no practical value.