science

Post-kala-azar dermal leishmaniasis

Post-kala-azar dermal leishmaniasis is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Post-kala-azar dermal leishmaniasis rather than just read about it. In short: Post-kala-azar dermal leishmaniasis (PKDL) is a complication of visceral leishmaniasis (VL); it is characterised by a macular, maculopapular, and nodular rash in a patient who has recovered from VL and who is otherwise well. The rash usually starts around the mouth from where it spreads to other parts of the body depending on severity.

Key takeaways

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Reproduce the core statement of Post-kala-azar dermal leishmaniasis from memory before moving on to harder problems.

Reference excerpt

Post-kala-azar dermal leishmaniasis (PKDL) is a complication of visceral leishmaniasis (VL); it is characterised by a macular, maculopapular, and nodular rash in a patient who has recovered from VL and who is otherwise well. The rash usually starts around the mouth from where it spreads to other parts of the body depending on severity. Post-kala-azar dermal leishmaniasis (also known as "Post-kala-azar dermatosis") found mainly on the face, arms, and upper part of the trunk. It occurs years (in the Indian variation) or a few months (in the African strain) after the successful treatment of visceral leishmaniasis. It is mainly seen in Sudan and India where it follows treated VL in 50% and 5–10% of cases, respectively. Thus, it is largely restricted to areas where Leishmania donovani is the causative parasite. The interval at which PKDL follows VL is 0–6 months in Sudan and 2–3 years in India. PKDL probably has an important role in interepidemic periods of VL, acting as a reservoir for parasites. PKDL was first identified by Sir Upendranath Brahmachari, who initially called it dermal leishmanoid. He published his observations in the Indian Medical Gazette in 1922.

Mechanism The cause of PKDL is uncertain. Possibilities may include use of antimonial drugs, sunburn, reinfection with kala-azar, memory T cell responses failing in certain organs; and genetic susceptibility. There is increasing evidence that the pathogenesis is largely immunologically mediated; high concentrations of interleukin 10 in the peripheral blood of VL patients predict the development of PKDL. During VL, interferon gamma is not produced by peripheral blood mononuclear cells (PBMC). After treatment of VL, PBMCs start producing interferon gamma, which coincides with the appearance of PKDL lesions due to interferon-gamma-producing cells causing skin inflammation as a reaction to persisting parasites in the skin.

Diagnosis PKDL is difficult to diagnose. Diagnosis is mainly clinical, but parasites can be seen by microscopy in smears with limited sensitivity. PCR and monoclonal antibodies may detect parasites in more than 80% of cases. Serological tests and the leishmanin skin test are of limited value.

Treatment Treatment is always needed in Indian PKDL; in Sudan, most cases are self-limited but severe and chronic cases are treated. Sodium stibogluconate is given at 20 mg/kg for 2 months in Sudan and for 4 months in India. Liposomal amphotericine B seems effective. Although research has brought many new insights in pathogenesis and management of PKDL, several issues in particular in relation to control remain unsolved and deserve urgent attention. Miltefosine is the only available oral medication available for VL and PKDL. While the drug works for short-term treatment of VL, PKDL would require a longer treatment of more than 28 days with this drug. Miltefosine is not recommended for use as a monotherapy to treat PKDL. The risk of human immunodeficiency virus (HIV) co-infection in patients with visceral leishmaniasis (VL) or kala-azar in endemic areas has posed a major challenge in control.

Society and culture People with PKDL are a reservoir of leishmaniasis. To eliminate leishmaniasis from a population, people with PKDL must get treatment. The government of India has an kala-azar elimination program ongoing which entered a consolidation phase in 2017.

Illustrations

Worked examples

Example 1 — a first encounter with Post-kala-azar dermal leishmaniasis

Start with the simplest possible case. Write down what Post-kala-azar dermal leishmaniasis claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Post-kala-azar dermal leishmaniasis before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Post-kala-azar dermal leishmaniasis ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Post-kala-azar dermal leishmaniasis

In research: Post-kala-azar dermal leishmaniasis appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Post-kala-azar dermal leishmaniasis in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Post-kala-azar dermal leishmaniasis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Leishmaniasis, Parasitic infestations, stings, and bites of the skin, so understanding it makes those chapters shorter.
In everyday life: Look for Post-kala-azar dermal leishmaniasis outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Post-kala-azar dermal leishmaniasis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Post-kala-azar dermal leishmaniasis means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
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Frequently asked questions

What is Post-kala-azar dermal leishmaniasis in simple terms?

Why does Post-kala-azar dermal leishmaniasis matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Post-kala-azar dermal leishmaniasis?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Post-kala-azar dermal leishmaniasis.