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PubMed This is a summary of 21 peer-reviewed journal articles Updated
Infectious Disease

The Science of the Spot: Symptoms and Biology

At a Glance

Hansen's disease (leprosy) targets the peripheral nervous system, causing hallmark symptoms like numb, discolored skin patches and enlarged nerves. Because it mimics common conditions like ringworm or vitiligo, early diagnosis through sensory testing and skin biopsy is crucial.

Hansen’s disease is often called “The Great Imitator” because its symptoms—skin patches and numbness—can look like many other common conditions [1][2]. Understanding how the bacteria specifically target your nerves and how to spot the unique “hallmark” signs can help you advocate for an accurate diagnosis.

The Biology: Why Numbness Happens

Hansen’s disease is unique because the bacteria, Mycobacterium leprae, have a “homing instinct” for the peripheral nervous system [3]. Specifically, they target Schwann cells—specialized cells that wrap around and protect your nerves like insulation on a wire [3][4].

When the bacteria invade these cells, they “reprogram” them, causing the insulation to break down and the nerve to become inflamed [3][5]. This damage interrupts the signals traveling to your brain, which is why the hallmark symptom of Hansen’s disease is anesthesia (a complete loss of sensation) in the affected area [6][7].

Hallmark Signs to Look For

While the disease can look different for everyone, doctors look for three primary “cardinal signs” [1][8]:

  1. Anesthetic Skin Patches: These are areas of skin that may be lighter (hypopigmented) or reddish (erythematous) [6]. Crucially, these patches lose the ability to feel light touch, heat, or pain [7][9].
  2. Enlarged Nerves: As the immune system fights the bacteria inside the nerve, the nerve can swell and become “thickened” [10][11]. A doctor can often feel these enlarged nerves near the elbow (ulnar nerve) or the side of the knee (common fibular nerve) [12][13].
  3. Presence of Bacteria: A definitive diagnosis is often made by finding the bacteria in a skin biopsy or a slit-skin smear (a small sample of fluid from the skin) [1][14].

Common Misdiagnoses

Because Hansen’s disease is rare in many areas, it is frequently mistaken for other conditions. Here is how it typically differs:

Condition Common Appearance Key Difference from Hansen’s Disease
Ringworm (Fungal) Red, itchy, circular scaly rings. Ringworm is usually very itchy; Hansen’s patches are rarely itchy and are numb [1].
Vitiligo Stark white patches of skin. Vitiligo involves a total loss of color (pigment) but retains full feeling [9].
Psoriasis Thick, silvery scales that may bleed. Psoriasis is typically painful or itchy and does not cause loss of sensation [15].
Diabetic Neuropathy Numbness in hands and feet. Diabetes usually causes a “stocking-glove” pattern (both feet or both hands); Hansen’s numbness is often tied to specific skin patches or individual nerves [16][17].

The Importance of Early Action and Nerve Recovery

If you have a skin lesion that does not heal with standard creams and feels numb to the touch, it is vital to ask your doctor specifically about Hansen’s disease [18][19].

While the nerve damage caused by M. leprae can become permanent if left untreated, early diagnosis and treatment can stop the damage from spreading [6][20]. A common question is: Will my feeling ever come back? The primary goal of treatment is to kill the bacteria and stop the numbness from getting worse. In some early cases, sensation may slowly return over months or years, but in many cases, the loss of feeling is permanent [21]. Stopping the progression early is the key to preventing long-term disability.

Common questions in this guide

Why does Hansen's disease cause numb skin patches?
The bacteria that cause Hansen's disease specifically target Schwann cells, which protect your nerves. When these cells are damaged, the nerve becomes inflamed and cannot send signals to your brain, resulting in a loss of feeling in the affected area.
How can I tell the difference between Hansen's disease and ringworm?
While both can cause circular skin patches, ringworm is typically very itchy. In contrast, skin patches caused by Hansen's disease are rarely itchy and usually lose their ability to feel light touch, heat, or pain.
What are the primary signs a doctor looks for to diagnose Hansen's disease?
Doctors look for three cardinal signs: skin patches with a loss of sensation, enlarged or thickened peripheral nerves, and the presence of the bacteria confirmed through a skin biopsy or slit-skin smear.
Will my feeling ever come back if I have Hansen's disease?
The main goal of treatment is to kill the bacteria and prevent symptoms from worsening. While sensation may slowly return in some early cases, the loss of feeling is often permanent, which makes early diagnosis very important.
Why is Hansen's disease often misdiagnosed?
Because Hansen's disease is rare in many areas, its skin patches and nerve symptoms are frequently mistaken for more common conditions like fungal infections, vitiligo, psoriasis, or diabetic neuropathy.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Can we perform a sensory test on my skin lesions to check for loss of temperature or pain sensation?
  2. 2.Would a skin biopsy or a slit-skin smear be appropriate to confirm the presence of Mycobacterium leprae?
  3. 3.Are you able to check my peripheral nerves (like the ulnar or fibular nerves) for thickening or enlargement?
  4. 4.How do we rule out other conditions like ringworm, vitiligo, or diabetic neuropathy in my case?
  5. 5.If my biopsy is negative for bacteria but my symptoms persist, what are the next steps for diagnosis?

Questions For You

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References

References (21)
  1. 1

    Clinico-Histological Correlation in Hansen's Disease: Three-year Experience at a Newly Established Tertiary Care Center in Central India.

    Semwal S, Joshi D, Goel G, et al.

    Indian journal of dermatology 2018; (63(6)):465-468 doi:10.4103/ijd.IJD_525_17.

    PMID: 30504973
  2. 2

    Pure neuritic leprosy presenting as ulnar nerve neuropathy: a case report of electrodiagnostic, radiographic, and histopathological findings.

    Payne R, Baccon J, Dossett J, et al.

    Journal of neurosurgery 2015; (123(5)):1238-43 doi:10.3171/2014.9.JNS142210.

    PMID: 26047418
  3. 3

    Cell Biology of Intracellular Adaptation of Mycobacterium leprae in the Peripheral Nervous System.

    Hess S, Rambukkana A

    Microbiology spectrum 2019; (7(4)) doi:10.1128/microbiolspec.BAI-0020-2019.

    PMID: 31322104
  4. 4

    Mycobacterium leprae induces Schwann cell proliferation and migration in a denervated milieu following intracutaneous excision axotomy in nine-banded armadillos.

    Ebenezer GJ, Pena MT, Daniel AS, et al.

    Experimental neurology 2022; (352()):114053 doi:10.1016/j.expneurol.2022.114053.

    PMID: 35341747
  5. 5

    Mycobacterium leprae-induced nerve damage: direct and indirect mechanisms.

    Serrano-Coll H, Salazar-Peláez L, Acevedo-Saenz L, Cardona-Castro N

    Pathogens and disease 2018; (76(6)) doi:10.1093/femspd/fty062.

    PMID: 30052986
  6. 6

    Functional Impairment of Skin Appendages Due to Peripheral Nerve Involvement by Mycobacterium leprae.

    Granger DL, Rosado-Santos H, Lo TS, et al.

    Open forum infectious diseases 2020; (7(10)):ofaa419 doi:10.1093/ofid/ofaa419.

    PMID: 33094119
  7. 7

    The Curse of the Nine-Banded Armadillo: Case Report and Review.

    Elsayed G, Elsayed M, Clincea R, et al.

    Military medicine 2015; (180(7)):e861-6 doi:10.7205/MILMED-D-14-00421.

    PMID: 26126264
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    Leprosy in the Heartland.

    Keegan A, Gubbrud J, Hockhausen K, Peck H

    South Dakota medicine : the journal of the South Dakota State Medical Association 2023; (76(11)):486-493.

    PMID: 38985957
  9. 9

    Beyond Classic Leprosy: Exploring Atypical Manifestations and Their Diagnostic Challenges.

    Bathina A, Kollipara H, Sravani G, Laxmi VS

    Cureus 2024; (16(12)):e75957 doi:10.7759/cureus.75957.

    PMID: 39834975
  10. 10

    Hansen's disease in the era of COVID-19: An observation on a series of six patients with co-infection.

    Arora S, Bhatnagar A, Singh GK, et al.

    Dermatologic therapy 2021; (34(2)):e14827 doi:10.1111/dth.14827.

    PMID: 33527634
  11. 11

    Point-of-care ultrasound of peripheral nerves in the diagnosis of Hansen's disease neuropathy.

    Voltan G, Filho FB, Leite MN, et al.

    Frontiers in medicine 2022; (9()):985252 doi:10.3389/fmed.2022.985252.

    PMID: 36160126
  12. 12

    Role of multisegmental nerve ultrasound in the diagnosis of leprosy neuropathy.

    De Martino Luppi A, Ferreira GE, Borges IS, et al.

    PloS one 2024; (19(7)):e0305808 doi:10.1371/journal.pone.0305808.

    PMID: 39024363
  13. 13

    Extensive sonographic ulnar nerve enlargement above the medial epicondyle is a characteristic sign in Hansen's neuropathy.

    Bathala L, N Krishnam V, Kumar HK, et al.

    PLoS neglected tropical diseases 2017; (11(7)):e0005766 doi:10.1371/journal.pntd.0005766.

    PMID: 28753608
  14. 14

    A Clinicohistopathological Correlation of Hansen's Disease in a Rural Tertiary Care Hospital of Central India.

    Atram MA, Ghongade PV, Gangane NM

    Journal of global infectious diseases 2020; (12(4)):191-196 doi:10.4103/jgid.jgid_58_20.

    PMID: 33888956
  15. 15

    Rare Masqueraders of Pure Neuritic Leprosy: A Report of Four Cases.

    Sadhukhan S, Bhardwaj A, Kumar S, et al.

    Indian dermatology online journal 2025; (16(2)):280-285 doi:10.4103/idoj.idoj_495_24.

    PMID: 40125031
  16. 16

    Unmasking Carpal Tunnel Syndrome by High-Resolution Ultrasonography in Misdiagnosed Pure Neuritic Leprosy: A Case Report.

    Dalave K, Patil P, Raman T, Agarwal U

    Cureus 2024; (16(7)):e65578 doi:10.7759/cureus.65578.

    PMID: 39192940
  17. 17

    Leprosy Mimicking Thrombangiitis Obliterans (Buerger's Disease): A Case Study.

    Sena CO, Goulart IMB, Justino Sena PC, et al.

    Cureus 2025; (17(3)):e80822 doi:10.7759/cureus.80822.

    PMID: 40255772
  18. 18

    Autochthonous borderline tuberculoid leprosy in a man from Florida.

    Villada G, Zarei M, Romagosa R, et al.

    Leprosy review 2016; (87(1)):101-3.

    PMID: 27255063
  19. 19

    Hansen's disease patient in Ohio successfully treated with a monthly rifampin, minocycline, and moxifloxacin regimen: a case report.

    Sankovic DE, Hubal AL, Alhajj MA, et al.

    ASM case reports 2025; (1(5)) doi:10.1128/asmcr.00080-24.

    PMID: 41244968
  20. 20

    Pathogenesis, Clinical Considerations, and Treatments: A Narrative Review on Leprosy.

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  21. 21

    Bilateral corneal perforation caused by neurotrophic keratopathy associated with leprosy: a case report.

    Iraha S, Kondo S, Yamaguchi T, Inoue T

    BMC ophthalmology 2022; (22(1)):42 doi:10.1186/s12886-022-02265-6.

    PMID: 35093062

This page provides educational information about the symptoms and biology of Hansen's disease (leprosy). It is not a substitute for professional medical advice, diagnosis, or treatment from a qualified healthcare provider.

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