Cutaneous leishmaniasis: A pathological study of 360 cases with special emphasis on the contribution of immunohistochemistry and polymerase chain reaction to diagnosis

Abstract

Background: Traditional methods for the diagnosis of leishmaniasis yield poor sensitivity, which limits its effectiveness in lesions with a low parasite burden. Methods: Retrospective pathologic study of 360 cases of cutaneous leishmaniasis and analysis of the different diagnostic methods used. Results: In 93% of the lesions, histopathology showed a dense and diffuse inflammatory infiltrate, consisting of lymphocytes, histiocytes and plasma cells, which occupied the superficial and mid dermis and variably extended to deep dermis and superficial subcutis (standard pattern). The remaining cases exhibited atypical features, such as perivascular, interstitial or perifollicular inflammatory patterns, folliculitis or panniculitis. Granulomas were identified in 84% of biopsies, most of them as small, poorly formed, non-necrotizing histiocytic aggregates. Amastigotes were visualized by routine histopathologic exam in 36% of biopsies. Immunohistochemistry stained 17 of 26 lesions (65%) negative by conventional stains. PCR provided the correct diagnosis in 218 cases (58% of the series) negative for Leishmania by other techniques. Conclusions: Biopsies negative for Leishmania by traditional diagnostic methods that show the histopathologic standard pattern, those with atypical features from patients with clinical suspicion of cutaneous leishmaniasis in endemic areas, should be studied by immunohistochemistry and/or PCR for Leishmania in order to reach the definitive diagnosis.

Imaging Leishmania major Antigens in Experimentally Infected Macrophages and Dermal Scrapings from Cutaneous Leishmaniasis Lesions in Tunisia

“…Our previous studies (carried out in the same epidemiological setting) already reported that this low parasite load was not detected by microscopy but was by conventional ITS1 PCR, a lower load not being detected by either technique [10]. This high sensitivity of the DIF assay, which reaches that of the molecular tool, corroborates results obtained with histopathological diagnosis [17,18,23], polyclonal antibodies produced against Leishmania showing higher Leishmania detection rate compared to monoclonal ones [26]. Thus when the parasite load is low and ordinary techniques such as Giemsa stains fail to detect the parasites, immunohistochemistry with anti-Leishmania antibodies has demonstrated a higher level of sensitivity in the identification of amastigotes [44,45].…”

“…The CL Detect™ Rapid Test (InBios, Washington, DC, USA) targeting the peroxidoxin antigen produced by Leishmania amastigotes in skin lesions has been evaluated in various endemic settings with varying results [15,16]. On the other hand, it is now recognized that immunohistochemistry (IHC) detecting Leishmania antigens in tissue sections is a reliable complementary tool improving sensitivity and specificity of the histopathological diagnosis of CL, especially for lesions with low parasite burden [17,18]. Monoclonal [19,20] and polyclonal antibodies [18,[21][22][23][24][25] produced against Leishmania, as well as immune serum from dog naturally infected with Leishmania [26], were successfully used to detect Leishmania amastigotes and their antigens in routinely prepared histological sections.…”

Overcoming the Negligence in Laboratory Diagnosis of Mucosal Leishmaniasis

“…Mucosal lesions usually have a low parasitic burden and sample collection for laboratory diagnosis is not an easy task, which are both factors that influence the low sensitivity of DP. Other laboratory tests, in addition to DP, are employed for ML diagnosis, such as histopathological tests, but biopsy is needed for this, resulting in an invasive and painful collection, which can only be performed by a specialist [ 29 ]. Besides, the result of the histopathological examination, in the absence of parasites in lesions and with the finding of diffuse granulomatous dermatitis, can be confused with other diseases [ 78 ], such as histoplasmosis, caused by Histoplasma capsulatum [ 79 , 80 ], a disease that can be found in endemic regions for TL, such as the Amazon.…”

“…Clinical examinations based on rhinoscopy or oropharyngoscopy are also useful for ML diagnosis. Thus, ML is a chronic lesion that is difficult to diagnose, due to the low parasitic load and the need for specialized professionals to collect the biological sample or perform the main examinations [ 29 ]. Among the options provided, PCR and conventional or quantitative methods are tests that have the greatest advantages in terms of sensitivity and specificity [ 30 , 31 , 32 , 33 ].…”

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“…Leishmaniasis is a common tropical disorder attributed to an obligate intracellular protozoan which is transmitted to humans by the bite of the Phlebotomus or Lutzomyia sand-fly and causes manifestations by which it is classified into the cutaneous, mucocutaneous, and visceral disease, parasitized macrophages with lymphocytic 7 infiltration or non-specific chronic inflammation. It is also associated with the formation of granulomas: these can vary from non-specific ill-defined 7,8 granulomas to epithelioid granulomas. Cases of cutaneous leishmaniasis have been demonstrated to show caseous necrosis as well, and have the 9 potential to be misdiagnosed as tuberculosis, or may be mischaracterized as a non-infectious disease 10 such as pyoderma gangrenosum.…”