Leishmaniasis (cutaneous)

[1]

Meet the patient

A 26-year-old soldier back from a six-month deployment in Afghanistan presents with a painless ulcer on his forearm that has been slowly enlarging for eight weeks. The lesion has a firm, heaped-up, indurated rim surrounding a crusted base — the cone of a volcano around its crater. He feels entirely well. The question this lesion plants is the question every leishmaniasis stem turns on: what species bit him, and does that species carry the latent threat of mucosal destruction?[3]

Across the ward, a 40-year-old farmer from Bihar lies febrile, cachectic, and grey-skinned, with a spleen crossing his umbilicus and a platelet count of 20. This is a different emergency entirely. Untreated, visceral leishmaniasis — kala-azar, Hindi for "black disease", from the grey hyperpigmentation of cachexia — is over 95 percent fatal within two years. The question he plants is operational: is this malaria, or is it the one febrile splenomegaly that an rK39 will catch and a short course of liposomal amphotericin will cure?[5]

Hold those two patients — the painless ulcer and the giant spleen — and the whole topic resolves into a single sentence: the species sets the syndrome, the host's cellular immunity sets the severity, and the morphology sets the diagnosis.[1]

One parasite, two faces — the spectrum in one breath

Leishmania is a single genus that wears many clinical faces, and which face appears is decided almost entirely by three things: the species, the host's cellular immune response, and the geography of exposure.[2]

A brisk Th1 response walls the parasite into a self-healing cutaneous ulcer; an anergic cellular response lets it flood the skin as diffuse nodular disease or seed the reticuloendothelial system to kill. Leishmania braziliensis alone carries the delayed threat of facial mutilation years after the skin has healed. The diagnostic signature — the amastigote, the Leishman-Donovan body, sitting inside a macrophage on Giemsa stain — is identical across every syndrome, because the parasite is identical; only the immune response differs.[4]

[2]

Old World vs New World — the face-off

The species is not a footnote — it is the single fact that decides the threat, the reservoir, and the therapy, and a fellowship candidate must hold both worlds in mind at once. Old World leishmaniasis spans the Mediterranean basin, the Middle East, North and sub-Saharan Africa, and Central Asia; New World leishmaniasis runs from Mexico to northern Argentina. The line that matters is L. braziliensis: its cutaneous lesions look trivial, yet years later they can destroy the face.[3]

[9]

The one-line discriminator beneath the table: New World disease from the L. braziliensis complex earns systemic therapy even when the skin lesion looks harmless, because the mucosal threat lives in the species, not in the lesion.[3]

The dimorphic life cycle — promastigote meets amastigote

Leishmania is dimorphic, and the two forms map exactly onto the two hosts and onto every diagnostic test you will be asked about.[9]

The face-off is the viva staple — name the form, name the host, name the test that finds it:[10]

[10]

The mechanism, told once: an infected female sandfly inoculates metacyclic promastigotes into the dermis along with her saliva, which is itself immunosuppressive. Dermal macrophages phagocytose them, and the parasite survives inside the hostile phagolysosome by deploying surface lipophosphoglycan to resist complement and blunt the oxidative burst. There it transforms into the amastigote, divides by binary fission until the macrophage ruptures, and the released organisms infect new macrophages — or are ingested by another sandfly, in which they transform back into promastigotes and complete the cycle.[9]

Etymology for viva gold: the order is Kinetoplastida, named for the kinetoplast — the rod of mitochondrial DNA visible beside the nucleus on Giemsa stain — which is the single feature that distinguishes Leishmania from Histoplasma on a smear. The Leishman-Donovan body carries the names of William Leishman and Charles Donovan, who independently described the causative organism of kala-azar in 1903.[10]

The immunity spectrum — CL, DCL, and VL are one dial

The clinical face of leishmaniasis is the visible readout of the host's cellular immune response. Turn the dial one way and the parasite is contained; turn it the other and it disseminates. This single spectrum is the conceptual key to the whole topic.[4]

[1]

The classic trap: diffuse cutaneous leishmaniasis — widespread anaesthetic-looking nodules teeming with parasites — is misread as lepromatous leprosy. The discriminator is the smear: DCL is stuffed with amastigotes (Leishman-Donovan bodies), while leprosy is stuffed with acid-fast bacilli. The wrong diagnosis sends the patient down a leprosy pathway for months while the leishmaniasis proliferates unchecked.[13]

Cutaneous leishmaniasis — the volcano sign and its variants

The signature lesion is a chronic, painless ulcer with a raised, indurated border and a crusted base on an exposed site — the volcano sign, named for the firm heaped-up inflammatory rim that resembles a volcanic cone around its crater.[1]

The lesion begins weeks to months after the bite as an erythematous papule at an exposed site — face, arms, or legs, never under clothing — enlarges into a nodule, then ulcerates. It is usually single but may be multiple, regional lymphadenopathy is common, and it is characteristically painless, which is why patients present late. Untreated it smoulders for months to years, then heals spontaneously with a depressed, disfiguring scar — most reliably in L. major and L. mexicana, less so in L. tropica and L. braziliensis.[3]

Etymology for viva gold: the volcano sign — the firm heaped rim around the central crater. Hold the image and you will not confuse cutaneous leishmaniasis with a pyoderma, a spider bite, or a staphylococcal ulcer, all of which hurt.[13]

The atypical cutaneous variants are high-yield, and each carries its species:[9]

[3]

Espundia — the mutilation that comes years later

Mucosal leishmaniasis (espundia) is the most feared complication of cutaneous disease, and it announces itself not with the ulcer but years to decades after the skin lesion has healed.[3]

The parasite, almost always L. braziliensis and occasionally L. panamensis, has persisted silently in mucosal tissue. It begins insidiously with nasal stuffiness and epistaxis, then progresses to destructive granulomatous inflammation: perforation of the nasal septum, erosion of the nasal alae, perforation of the palate, and destruction of the lips, uvula, and larynx. The end-state — the tapir nose deformity — is profoundly disfiguring, threatens the airway, and is refractory and recurrent even after adequate therapy.[4]

The classic trap: a returned soldier with a perforated nasal septum years after a healed Brazilian skin ulcer is sent to the ENT clinic as Wegener granulomatosis or a midline lymphoma. The Latin American exposure and the prior skin lesion make espundia the diagnosis; biopsy shows amastigotes and granulomas, and ANCA is negative. Treating it as autoimmune disease with immunosuppression is catastrophic.[13]

The defensive reflex that prevents this trap: screen the nasal and oropharyngeal mucosa in every New World cutaneous case — septal crusting or perforation, palatal ulceration, epistaxis — because the earliest mucosal signs can appear while the skin still looks healed.[3]

Kala-azar — the kill-or-cure emergency

Visceral leishmaniasis is uniformly fatal untreated — over 95 percent mortality within two years — and yet is among the most curable infections in medicine when caught. There is no room for diagnostic delay.[5]

The classic tetrad is irregular (often biphasic) fever, massive splenomegaly with or without hepatomegaly, pancytopenia, and progressive cachexia. The spleen is characteristically massive, soft, and non-tender, crossing the umbilicus in advanced disease. Secondary features complete the picture: polyclonal hypergammaglobulinaemia (which produces a falsely positive rheumatoid factor and a high erythrocyte sedimentation rate), hypoalbuminaemia with oedema, bleeding from thrombocytopenia, diarrhoea, and the greyish skin hyperpigmentation that gives the disease its name.[1]

Etymology for viva gold: kala-azar is Hindi for black disease, from the grey-brown hyperpigmentation of sun-exposed skin in cachectic patients — the sign that named the syndrome before the parasite was known.[5]

The classic trap: the febrile, splenomegalic returned traveller or endemic resident labelled malaria or typhoid on a single negative smear, without an rK39. In an endemic region, visceral leishmaniasis is the one febrile splenomegaly that a bedside rapid test will catch and a short course of liposomal amphotericin will cure; missing it is a preventable death.[6]

Post-kala-azar dermal leishmaniasis — the eruption that bridges epidemics

PKDL is a dermal eruption that appears after a patient has been treated and apparently cured of visceral leishmaniasis — and its importance is epidemiological as much as clinical, because the parasites in its skin are the bridge between one epidemic and the next.[7]

It presents as hypopigmented or erythematous macules, papules, and nodules on the face, trunk, and extremities — mimicking leprosy, melasma, or a drug eruption. The timing is geography-dependent: in India it appears 6 months to 3 years after VL; in Sudan it can appear during or soon after treatment and runs a more inflammatory course. Because PKDL patients carry parasites in apparently normal skin, they are the reservoir that sustains anthroponotic L. donovani transmission between epidemics — which is exactly why the Indian and Sudanese elimination programmes hunt and treat PKDL as aggressively as active VL.[8]

Diagnosis — Giemsa LD bodies, NNN culture, PCR, and rK39

The diagnosis rests on demonstrating the parasite or its genome in tissue, supported by serology for visceral disease — and because the species decides the therapy, PCR speciation is no longer optional in the returned traveller.[3]

For cutaneous disease, sample the active ulcer edge, never the necrotic base where organisms are scarce, and divide the tissue for three simultaneous tests:[10]

• Giemsa-stained smear — the quickest, most widely available test. It shows the amastigotes (Leishman-Donovan bodies) as 2 to 5 micrometre round organisms inside macrophages, each with a nucleus and the rod-shaped kinetoplast — the feature that distinguishes Leishmania from Histoplasma.
• Histopathology of a punch biopsy — a granulomatous dermatitis with epithelioid macrophages, lymphocytes, and plasma cells, and amastigotes within macrophages; it distinguishes CL from cutaneous tuberculosis and leprosy.
• Culture on Novy-MacNeal-Nicolle (NNN) medium at 22 to 26 degrees Celsius for up to 4 weeks — yields the motile promastigote, the gold standard but slow and laboratory-demanding.
• PCR (kinetoplast DNA or the internal transcribed spacer) — the most sensitive method and the only one that species-identifies, which in turn guides therapy (L. major may be observed; L. braziliensis earns systemic therapy).[3]

For visceral disease, demonstrate parasites in reticuloendothelial tissue or use the field rapid test in the right clinical context:[5]

• Bone marrow aspirate (sensitivity 60 to 85 percent) or splenic aspirate (sensitivity over 95 percent, the gold standard, but carrying a bleeding risk — check the platelet count and coagulation first).
• rK39 rapid diagnostic test — a lateral-flow antibody test for field diagnosis of VL in South Asia and the Mediterranean; highly sensitive in symptomatic disease. The direct agglutination test (DAT) is the reference-laboratory alternative.
• PCR on blood or marrow — highly sensitive, and invaluable for diagnosing and monitoring relapse, especially in HIV co-infection.[1]

[10]

The Montenegro test (leishmanin skin test) — an intradermal delayed-type hypersensitivity test analogous to the Mantoux — is positive in cutaneous and healed disease but cannot distinguish past from active infection, so it is now used for epidemiological surveys rather than individual diagnosis.[9]

[5]

The treatment ladder — when to watch, when to treat locally, when to go systemic

Therapy is decided by four facts: the syndrome, the species, the site, and the host. The candidate who knows when to do nothing, when to treat locally, and when to commit to systemic therapy has mastered the management question.[3]

[11] [5]

Diffuse cutaneous leishmaniasis (L. aethiopica or L. amazonensis) is refractory and demands combination therapy — typically paromomycin plus sodium stibogluconate for 60 days or longer, or liposomal amphotericin B — and even so, relapse is the rule.[1]

VL — liposomal amphotericin is the gold standard

Liposomal amphotericin B is the global gold standard for visceral leishmaniasis, reflecting both efficacy (cure over 95 percent) and a far better safety profile than conventional amphotericin or the antimonials it replaced.[1]

The driving force behind the switch was antimonial resistance in Bihar, India, where up to 60 percent of VL was once unresponsive to pentavalent antimonials — a resistance born of community-level misuse that made the cheap drug useless in the very region that needed it most. Liposomal amphotericin, donated to endemic countries through the WHO, displaced antimonials as first-line.[5]

Combination therapy — liposomal amphotericin B plus miltefosine, or miltefosine plus paromomycin — shortens the course, reduces each component's dose and toxicity, and lowers the risk of resistance; it is endorsed by the WHO and the DNDi and underpins the regional elimination programmes.[1]

In anthroponotic VL regions such as India, there is a public-health reflex alongside the clinical one: the case is reported to the National Vector-Borne Disease Control Programme (NVBDCP) for active case detection, indoor residual spraying, and the elimination programme.[5]

HIV co-infection — the amplifier

Visceral leishmaniasis is an AIDS-defining illness, and HIV is the most important biological amplifier of leishmaniasis on the planet — the two diseases feed each other in a vicious cycle.[4]

VL in HIV-positive patients may present without massive splenomegaly, may seed atypical sites (the gastrointestinal tract, the skin), responds poorly to therapy, and relapses in over 50 percent within a year. Management pairs antileishmanial therapy (liposomal amphotericin B preferred) with early antiretroviral therapy, and most guidelines recommend secondary prophylaxis with monthly liposomal amphotericin B until immune reconstitution is sustained. The immunosuppressed transplant recipient or patient on anti-TNF therapy may suffer reactivation of latent infection.[6]

Preventable harm — the kill-or-cure checklist

This is the list a senior expects you to recite without notes, because every item is a death or a mutilation that the right reflex prevents:[1]

• Death from untreated visceral leishmaniasis — the febrile splenomegalic patient sent home as malaria without an rK39.
• Mutilation from delayed mucosal therapy — the L. braziliensis skin lesion treated as cosmetic, surfacing years later as espundia.
• The missed HIV-VL co-infection — VL treated without an HIV test, relapsing without secondary prophylaxis.
• The leprosy misdiagnosis of diffuse cutaneous leishmaniasis — nodular leishmaniasis sent down a leprosy pathway while parasites proliferate.
• Antimonial cardiotoxicity — sudden death from torsades in a patient on pentavalent antimonials without ECG monitoring.
• Miltefosine in pregnancy — a teratogenic exposure because contraception was not secured.[13]

Regional and public-health deltas

The diagnostic and treatment framework is globally consistent, but the species, the reservoir, and the elimination strategy differ by region — and the public-health reflex matters as much as the drug.[1]

[5]

Prevention — three pillars, no vaccine

There is no licensed human vaccine, so prevention rests on three pillars: vector control, reservoir control, and personal protection.[2]

Vector control is the population backbone: indoor residual spraying in anthroponotic VL regions, insecticide-treated bed nets (sandflies bite from dusk to dawn, rest near the ground, and are weak fliers), and environmental management around dwellings. Reservoir control targets the domestic dog in zoonotic L. infantum regions (insecticidal collars, vaccines, culling in Brazil) and rodents in zoonotic L. major foci. Personal protection — insect repellent (DEET), long sleeves and trousers, and fine-mesh bed nets — matters for travellers, soldiers, and forest workers, because sandflies are small enough to pass through standard mosquito netting.[6]

The mantra, and the mnemonic

The mantra: painless chronic ulcer in a returned traveller is leishmaniasis until proven otherwise; the species decides the threat.[1]

[12] [4]

Ward-round test — three stems

Stem 1 — the soldier's ulcer (answer)

A 26-year-old soldier back from Afghanistan has a painless ulcer with a raised indurated border on his forearm for eight weeks. Giemsa smear of the ulcer edge shows intracellular amastigotes. Name the likely species, the signature finding, and the management. Model: This is cutaneous leishmaniasis from L. major (Old World, rural, Middle East — a soldier's deployment to Afghanistan is classic). The signature is the amastigote (Leishman-Donovan body) inside a macrophage on Giemsa stain, identified by its nucleus and rod-shaped kinetoplast. A small, cosmetically unimportant L. major lesion may be managed by watchful waiting (it self-heals in over 70 percent within 6 to 18 months) or local therapy (cryotherapy, thermotherapy, topical paromomycin 15 percent twice daily for 20 days, or intralesional antimonials). Systemic therapy is reserved for large, facial, or non-healing lesions.[3]

[11]

Stem 2 — the perforated septum, years later (answer)

A returned soldier presents with epistaxis and a perforated nasal septum three years after a healed Brazilian skin ulcer on his leg. The registrar wants to treat Wegener granulomatosis. What is the diagnosis, and what is the trap? Model: This is mucosal leishmaniasis (espundia) from L. braziliensis, surfacing years after the healed cutaneous lesion. The trap is misreading it as granulomatosis with polyangiitis or a midline lymphoma and treating with immunosuppression, which is catastrophic. The Latin American exposure and the prior skin lesion make the diagnosis; biopsy shows amastigotes and granulomas, and ANCA is negative. Treat with prolonged systemic therapy for 28 days — pentavalent antimonials, liposomal amphotericin B, or miltefosine — with ENT and maxillofacial surgery for the airway and later reconstruction, but only after parasitological cure.[4]

[13]

Stem 3 — the farmer with the giant spleen (answer)

A 40-year-old farmer from Bihar is febrile, cachectic, and grey-skinned, with a spleen crossing the umbilicus and a platelet count of 20. Name the diagnosis, the bedside test, the gold-standard confirmatory test, and the treatment of choice. Model: This is visceral leishmaniasis (kala-azar) from L. donovani (anthroponotic, endemic in Bihar), suggested by the tetrad of fever, massive splenomegaly, pancytopenia, and cachexia with greyish hyperpigmentation — kala-azar, Hindi for black disease. The bedside test is the rK39 rapid immunochromatographic test. The gold-standard confirmatory test is amastigotes (Leishman-Donovan bodies) in a bone marrow or splenic aspirate (splenic sensitivity over 95 percent, but check platelets and coagulation first). The treatment of choice is liposomal amphotericin B (single 10 mg/kg dose under the Indian NVBDCP, or 3 mg/kg/day for 7 days per WHO) — preferred over antimonials because of Bihar resistance. Test for HIV: VL is AIDS-defining.[5]

[7]

Leishmaniasis rewards the candidate who reads the species and the immune response from the morphology: a volcano-sign ulcer on a soldier's forearm, a mutilated nose years after an Amazonian sore, a farmer with a giant spleen and a grey face, a child with hypopigmented macules after cured kala-azar. Hold the Old World and New World species, the dimorphic life cycle, the amastigote-on-Giemsa signature, and the stepwise ladder from watchful waiting to liposomal amphotericin — and the topic is yours.[1]

References

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12. [12][No authors listed]. Miltefosine 2012.PMID 31643403
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