This case report presents a difficult-to-diagnose case of American tegumentary leishmaniasis (ATL) caused by Leishmania (Viannia) guyanensis in a 24-year-old Hispanic male with a travel history to the Panama jungle, an endemic region for tropical infectious diseases. The patient initially presented with persistent skin lesions that progressed to abscesses with ulceration. Despite negative initial diagnostic tests, including microbiological investigations and histopathological examination, a comprehensive diagnostic workup and subsequent polymerase chain reaction (PCR) confirmed the presence of Leishmania parasites. This case underscores the need to consider tropical infectious diseases despite initial negative tests. Accurate species identification is vital for proper drug treatment, with miltefosine as an emerging option. Early, precise diagnosis and tailored management are essential for successful treatment. This report emphasizes the significance of conducting a comprehensive diagnostic workup, including PCR, in individuals with a history of travel to endemic regions, to accurately diagnose and effectively manage complex infectious diseases.

BACKGROUND: Leishmaniasis is a parasitic disease affecting both animals and humans, acquired with the bite of sand flies or, in Injection Drug Users (IDUs), with contaminated needles, still hypoendemic in Sicily and the Mediterranean basin. Even though it is responsible for 20,000 to 40,000 deaths per year, this parasitic infection is still considered a neglected tropical disease. People Living with HIV (PLWH) are considered at high-risk of developing Leishmaniasis and, despite the introduction of Highly Active Anti-Retroviral Therapy (HAART), mortality rate and relapses prevalence are still high in coinfected people.
METHODS: We present a case of HIV-Leishmania coinfection, posing the attention on the atypical signs and symptoms and the importance of thinking about other causes than the HIV infection progression when the patient presents with a worsening of his immune status during HAART.
CONCLUSIONS: This parasitic disease has a high mortality rate, so it is mandatory to think about it in all the patients having a low CD4+ T-cell count and an inverted CD4/CD8 ratio under HAART.

T1/ST2 is a surface marker selectively expressed on type 2 helper (TH2) effector cells. As Leishmania infection in susceptible BALB/c mice have ascribed to a polarized TH2 response, this study aim to investigate the T1/ST2 (the receptor for IL-33), as a typical TH2 marker in the postulation that a shift towards a beneficial TH1 response would occur in the absence of ST2. For this, ST2 knockout (ST2-/-) and WT BALB/c mice were experimentally infected in the retro-orbital sinus with L. infantum. We showed that ST2-/- animals displayed better control of parasite burden in both spleen and liver tissues at different time points of chronic phases, and reduced spleenomegaly and hepatomegaly compared with the wild-type (WT) mice. This was associated with increased in the IFN-γ levels and expression by CD4+ and CD8+ lymphocytes. The inflammatory response encompasses transaminases (AST and ALT) releases and NO productions were remarkably lower in ST2-/- mice compared with WT. These data suggest that, ST2-/-) exert protection against L. infantum infection and probably shift the immune response toward TH1 induction.