Cutaneous leishmaniasis by Leishmania infantum: behind granulomatous lesions of unknown aetiology.

BACKGROUND: Cutaneous leishmaniasis (CL) is underestimated in Spain as in other European countries due to the polymorphism of its clinical manifestations and histopathological features discouraging doctors from suspecting leishmaniasis. Mucosal manifestations (ML) are misdiagnosed due to the fact that they often mimic cancer.

OBJECTIVES: Given that leishmaniasis may be masked as different granulomatous diseases in Leishmania infantum endemic areas, the aim of this study was to verify this misdiagnosing and contributes to the improvement of CL/ML diagnosis.

METHODS: A retrospective study involving formalin-fixed paraffin-embedded tissue biopsies with histopathological features of granulomatous lesions of unknown origin (GLUO) detected in 17 patients. This study included 13 patients with CL that was used as positive controls, nine patients with other confirmed diseases used as negative controls and seven patients with histological features suggestive of CL or ML without confirmation. Molecular analysis was blindly performed using two different PCR techniques.

RESULTS: The PCR detected 15 CL cases in which the diagnosis was neither clinically nor histologically suspected. Leishmaniasis was confirmed in seven suspected patients in whom the classical techniques failed to detect the parasite. L. infantum was identified in all cases. A systematic review of CL cases in GLUO patients from European countries identified 45 reported cases.

CONCLUSIONS: In L. infantum endemic areas, a high percentage of GLUO are due to Leishmania infection. The main consequences are delayed diagnosis and underestimation of the real incidence. PCR performed on paraffin-embedded tissue proved to be a reliable tool for diagnosis of CL/ML and must be performed routinely in any granulomatous dermatitis, even when the morphological features are no stereotypical of leishmaniasis.