The particular manifestations of the disease in any single individual are determined by a complex interaction between the species of Leishmania and the genetic and immunological status of the host . 4 This was evident in our case series , as one patient presented with abundant parasitic organisms in the skin biopsy that were easily diagnosed by light microscopy , and the other patients had more advanced inflammatory reactions , with one displaying necrotizing granulomas and an absence of visible organisms . Since cutaneous leishmaniasis is rarely encountered by physicians in the U . S . and is almost always limited to patients with a history of travel to endemic areas , the third patient ’ s diagnosis could easily have been missed if the travel history was not revealed and the other travel companions had not been seen previously at the same clinic .
Figure 2 : Histiocytic inflammation with abundant parasites in skin biopsy of initial patient . Arrow points to a macrophage containing numerous dot-like parasitic organisms ( H & E stain ).
transmitted through the bites of infected female phlebotamine sandflies , which feed on blood to produce eggs . Only a small fraction of people infected by Leishmania develop disease , which manifests in three main forms : visceral , cutaneous , and mucocutaneous . Cutaneous leishmaniasis is the most common form . 1
Diagnosis of cutaneous leishmaniasis typically involves clinical suspicion of the disease and identification of parasitic organisms in a skin biopsy . When parasites are few or absent in tissue sections , molecular techniques ( typically PCR ) have been shown to be the most sensitive method for diagnosis . Additionally , molecular testing allows typing of the Leishmania species , which is important for determining optimal treatment and disease prognosis .
Immunohistochemical methods for identifying the parasites in tissue sections may be useful in some situations but are not widely available , particularly in countries where the disease is rare . 2
The usual clinical course of cutaneous leishmaniasis in symptomatic patients presents within one week to three months following a bite by an infected sandfly . Initially , a red papule appears at the site of the bite , which enlarges to form a plaque or nodule . Progression to a well-circumscribed , crusted ulcer with violaceous hypertrophied borders occurs over time and is usually followed by an atrophic scar at the site of the bite . 3
The typical histopathological picture evolves from an early stage with numerous amastigotes ( the diagnostic form of the parasite ), primarily within macrophages , to a dense mixed inflammatory infiltrate . Superficial dermal edema may be followed by epidermal ulceration and eventual granulomatous inflammation . As the inflammatory process progresses , the number of parasitic organisms in the skin generally decreases over time , usually to a point where they cannot be identified histologically . 4
Despite the typical clinical and histologic picture described above , diagnosis can be difficult due to the wide range of clinical and histopathological manifestations , which may imitate other inflammatory or neoplastic processes . Clinically , lesions may mimic a wide variety of entities , including squamous cell carcinoma , sarcoidosis , lymphoma , atypical mycobacterial infection , cutaneous lupus erythematosus , deep fungal infection , and tuberculosis . Diagnosis can be even more challenging if the number of amastigotes is low or absent in tissue sections , and lesions may be mistaken on histologic evaluation for a variety of other conditions also , including squamous cell carcinoma , deep fungal infection , secondary syphilis , panniculitis , tuberculosis , mycosis fungoides , and sarcoidosis . 3
In summary , the diversity of clinical and histopathological features of cutaneous leishmaniasis can lead to missed or delayed diagnosis and treatment , increasing the risk for progression of the disease . Our case series highlights the importance of knowing a patient ’ s travel history and maintaining a high index of clinical suspicion for parasitic infections in endemic regions outside of the U . S .
References
1 . World Health Organization Fact Sheet . ( 2 March 2020 ). Leishmaniasis . Retrieved from http :// www . who . int / news-room / fact-sheets / detail / leishmaniasis . Accessed 2 February 2021 .
2 . Cardozo RS , Garcia-Montero PP , Chicharro C . Tardio JC . Cutaneous leishmaniasis : A pathological study of 360 cases with special emphasis on the contribution of immunohistochemistry and polymerase chain reaction to diagnosis . J Cutan Pathol . 2020 ; 47 ( 11 ): 1018-1025 . https :// doi . org / 10.1111 / cup . 13785 .
3 . Saab J , Fedda F , Khattab R , Yahya L , Loya A , Satti M , A-G Kibbi , Houreih MA , Raslan W , El-Sabban M , Khalifeh I . Cutaneous leishmaniasis mimicking inflammatory and neoplastic processes ; a clinical , histopathological and molecular study of 57 cases . J Cutan Pathol 2012 ; 39 : 251-262 . https :// doi . org / 10.1111 / j . 1600-0560.2011.01844 . x .
4 . Hepburn N C . Cutaneous leishmaniasis : an overview . J Postgrad Med [ serial online ] 2003 [ cited 2020 Jul 2 ]; 49:50 . Available from : http :// www . jpgmonline . com / text . asp ?
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