Overview
Leprosy, also called Hansen disease, is a long-lasting infection caused by very slow-growing bacteria that attack the skin, the nerves just beneath it, the lining of the nose and the eyes.
Two facts matter more than any others. Leprosy is curable with antibiotics that WHO provides free of charge. And WHO states that it does not spread through casual contact, so the isolation and exclusion that people affected by leprosy still face have no medical basis at all.
Disease Summary
- Category
- Infectious Disease
- Cause
- Mycobacterium leprae
- Transmission
- Droplets from the nose and mouth during prolonged close contact
- Body System
- Skin
- Preventable
- Yes
- Curable
- Yes
Symptoms
Common Symptoms
Symptoms develop slowly. CDC states that it may take up to 20 years after contact with the bacteria for signs of the disease to appear.
Pale or Discoloured Skin Patches
WHO names a pale or reddish skin patch as one of the cardinal signs of leprosy.
Loss of Feeling in Those Patches
This is what separates leprosy from ordinary skin conditions. WHO’s first cardinal sign is definite loss of sensation in the patch.
Thickened or Enlarged Nerves
CDC describes enlarged nerves usually found around the elbows, knees and the side of the neck. WHO counts this among the cardinal signs.
Lumps Under the Skin or on the Face and Earlobes
CDC describes firm rounded bumps under the skin and painless swelling or lumps on the face or earlobes.
Thick, Stiff or Dry Skin
Listed directly by CDC among the signs of leprosy.
Painless Ulcers on the Soles of the Feet
These develop because the feet have lost sensation, so injuries go unnoticed.
Blocked Nose or Nosebleeds
CDC lists both, reflecting involvement of the lining of the nose.
A Very Long Silent Period
CDC states it may take up to 20 years after contact with the bacteria to develop signs of the disease, because the bacteria divide only about once every 13 days.
Danger Signs
Seek urgent medical attention immediately if any of the following symptoms develop.
New Weakness or Paralysis in the Hands or Feet
CDC lists muscle weakness and paralysis, especially in the hands and feet. This signals active nerve damage that can become permanent.
Eye Problems or Changes in Vision
CDC lists eye problems that may lead to blindness. Any change needs urgent assessment.
Loss of Eyebrows or Eyelashes, or Facial Swelling
Both indicate advancing disease and the need for prompt treatment.
New Pain, Swelling and Fever During or After Treatment
These are leprosy reactions, recognised episodes of inflammation that can accelerate nerve damage and that need medical management.
Sores on the Feet That Will Not Heal
CDC lists chronic non-healing foot sores, which follow the loss of sensation in the feet.
Diagnosis
Clinical Diagnosis on the Cardinal Signs
WHO states that leprosy is diagnosed clinically. The three cardinal signs are loss of sensation in a pale or reddish patch, a thickened nerve with loss of sensation or muscle weakness, and bacteria seen on a skin smear.
Testing Sensation in the Patches
Loss of feeling in a specific patch, rather than the patch itself, is the finding that points to leprosy.
Examining the Peripheral Nerves
The nerves at the elbow, knee and side of the neck are felt for thickening, and the muscles they supply are tested.
Classification for Treatment
WHO separates cases with one to five skin lesions and no bacteria seen, from cases with more than five lesions, nerve involvement or visible bacteria. This decides how long treatment lasts.
Assessment of Existing Disability
Disability is graded at diagnosis, both to plan care and because WHO uses it as the measure of how late cases are being found.
Laboratory Tests
Slit-Skin Smear
WHO counts finding the bacteria on a skin smear as one of the cardinal diagnostic signs. CDC states that the presence of acid-fast bacteria confirms the diagnosis.
Skin Biopsy
Shows the characteristic changes in the tissue and the bacteria within it. Used when the smear is negative but leprosy is still suspected.
Acid-Fast Staining
The staining method that makes the bacteria visible under the microscope.
Nerve Biopsy
Reserved for cases where nerve involvement is suspected but the skin findings are inconclusive.
Molecular Test
Detects the genetic material of the bacteria. CDC notes it is available only in specialised laboratories.
Treatment
Multidrug Therapy
WHO’s combination of dapsone, rifampicin and clofazimine kills the bacteria, cures the infection and stops transmission. WHO states that transmission ceases once treatment begins.
Free Supply of Treatment
WHO has provided multidrug therapy free of charge for decades. Cost should never be the reason someone goes untreated.
Management of Leprosy Reactions
Episodes of inflammation during or after treatment are managed actively, because they are a major cause of nerve damage.
Protecting Hands, Feet and Eyes
Once sensation is lost, injuries go unnoticed. Daily checking, proper footwear and eye protection prevent most of the disability people associate with leprosy.
Surgery and Rehabilitation
Reconstructive surgery, physiotherapy and assistive devices restore function where nerve damage has already occurred.
Prevention
Screening the contacts of every case
WHO recommends screening household, neighbourhood and social contacts of people diagnosed with leprosy.
Preventive treatment for contacts
WHO recommends a single dose of rifampicin for screened contacts as post-exposure prophylaxis. This is prevention, not treatment of illness.
Early diagnosis and prompt treatment
WHO states that transmission stops once treatment begins, so treating cases quickly protects the whole community.
Active case finding in endemic communities
Looking for cases rather than waiting for people to present is what finds leprosy before nerves are damaged.
No isolation is needed
WHO states leprosy does not spread through casual contact, so separating people affected by leprosy from their families serves no medical purpose.
Awareness of the cardinal signs
A patch of skin that has lost feeling is the sign communities can be taught to recognise and act on.
Risk Factors
Close Contacts of Untreated Cases
CDC states that prolonged, close contact with someone with untreated leprosy over many months is required to catch it.
- Household members of an untreated case
- Neighbours and close social contacts
- Contacts benefit most from screening, because early detection prevents disability
- Risk comes from duration and closeness of contact, never from casual contact
People in Endemic Countries
WHO reports that leprosy occurs in more than 120 countries.
- Communities in the highest-burden countries
- African countries reporting over 1 000 cases each year
- Remote rural areas where diagnosis is delayed
- Communities where the cardinal signs are not widely recognised
Children in Endemic Areas
Cases in children indicate recent and ongoing transmission in the community.
- WHO reported 9 397 new child cases worldwide in 2024
- Children in households with an untreated case
- Children whose skin patches are dismissed as fungal infection
- Early detection in children prevents a lifetime of disability
People Diagnosed Late
Delay, not the disease itself, is what causes disability.
- Anyone who already has visible disability when first diagnosed
- People whose numb patches were treated as something else for months or years
- People who avoided care because of stigma
- People who stopped treatment before completing the course
Complications
Permanent Nerve Damage
Loss of sensation and muscle power in the hands and feet is the central complication, and it is what all early treatment aims to prevent.
Visible Disability
WHO counted 9 157 new cases worldwide in 2024 that already had visible disability at diagnosis, including 2 919 in the African Region.
Blindness
CDC lists eye problems that may lead to blindness among the consequences of untreated leprosy.
Shortening of Fingers and Toes
CDC describes reabsorption of tissue causing shortened digits in advanced untreated disease. It follows repeated unnoticed injury, not the bacteria eating flesh.
Chronic Foot Ulcers
Sores on numb feet that do not heal, which are the commonest long-term problem.
Leprosy Reactions
Episodes of inflammation during or after treatment that can rapidly worsen nerve damage if not treated.
When to Seek Medical Care
A Skin Patch That Has Lost Feeling
This is the single most specific reason to be assessed for leprosy.
Numbness, Tingling or Weakness in Hands or Feet
These indicate nerve involvement and should be checked promptly.
If You Live With or Near Someone Being Treated for Leprosy
WHO recommends contact screening and preventive treatment, so present for screening rather than waiting for symptoms.
Painless Ulcers on the Feet, or Lumps on the Face or Earlobes
Both are listed by CDC among the signs of leprosy.
New Pain, Swelling or Fever While on Treatment
This may be a leprosy reaction and needs treatment of its own.
Prognosis
Cure Is the Expected Outcome
WHO states that leprosy is curable and that treatment in the early stages can prevent disability. CDC states the illness can be cured if treatment is completed as prescribed.
Timing Decides Whether Disability Follows
Nerve damage that has already happened may not reverse, which is why the interval between the first patch and diagnosis matters so much.
Transmission Stops When Treatment Starts
WHO states this directly. A person on treatment is not a risk to their family.
Relapse Is Uncommon After Full Treatment
Completing the full course is what makes recurrence unlikely.
Differential Diagnosis
Fungal Skin Infection
Causes scaly discoloured patches, but sensation in the patch is normal. This is the commonest condition leprosy is mistaken for.
Cutaneous Leishmaniasis
Also causes chronic skin lesions in tropical settings, and is diagnosed by finding a different parasite.
Vitiligo and Other Pale Patches
Loss of skin colour without loss of feeling points away from leprosy.
Psoriasis
Produces well-defined plaques, but they are not numb and the nerves are not thickened.
Nerve Tumours
Produce lumps along nerves that can mimic nerve thickening, but testing for the bacteria is negative.
References
World Health Organization: Leprosy
WHO fact sheet on cause, cardinal signs, multidrug therapy, prevention and stigma.
CDC: Clinical Overview of Leprosy
Classification, diagnosis, laboratory confirmation, reactions and treatment.
CDC: Signs and Symptoms of Leprosy
The skin, nerve and eye signs of leprosy and the consequences of leaving it untreated.
WHO Regional Office for Africa: Leprosy
Case numbers and disability figures for the African Region and the countries most affected.
Frequently Asked Questions
Is leprosy contagious?
Only with prolonged close contact with an untreated person. WHO states it spreads through droplets from the nose and mouth of an untreated case and that it does not spread through casual contact. CDC states you must have close contact over many months. Transmission stops once treatment begins.
Can leprosy be cured?
Yes. WHO’s multidrug therapy combines dapsone, rifampicin and clofazimine, taken by mouth for 6 months in cases with few lesions and 12 months in cases with more extensive disease. WHO provides this treatment free of charge.
How long after exposure do symptoms appear?
It can be many years. CDC states it may take up to 20 years after contact with the bacteria to develop signs of the disease, because the bacteria divide only about once every 13 days. That long delay is why screening contacts matters more than waiting for symptoms.
Will leprosy leave me disabled?
Not if it is caught early. WHO states that treatment in the early stages can prevent disability. Damage already done to a nerve may not reverse, which is why WHO tracks how many people already have visible disability when they are first diagnosed.
A family member has leprosy. Do I need anything?
You should be screened. WHO recommends screening household, neighbourhood and social contacts, together with a single dose of rifampicin as preventive treatment. This is for people who are not ill, and it is different from the multidrug therapy given to someone who has the disease.