Paucibacillary Vs Multibacillary Leprosy: Know the Differences

Paucibacillary Vs Multibacillary Leprosy: This chronic bacterial illness is classified into two types: Paucibacillary and Multibacillary Leprosy. Paucibacillary leprosy is a less severe variant that causes fewer than five skin lesions and usually results in negative bacterial testing. Multibacillary leprosy, on the other hand, is characterised by broad infection, frequently including more than five lesions, and may result in positive bacterial testing. This difference is critical for deciding treatment length, as paucibacillary leprosy requires a shorter period.

Difference Between Paucibacillary and Multibacillary Leprosy

Paucibacillary and multibacillary leprosy are classifications of leprosy based on the number of bacteria present in the lesions and the immune response of the patient. Highlighting the differences Between the two:


Paucibacillary Leprosy

Multibacillary Leprosy


A form of leprosy characterized by a low bacterial load

A form of leprosy characterized by a high bacterial load

Bacillary load



Skin lesions

Few and well-defined

Numerous and poorly defined

Skin involvement

Limited to a few areas

Extensive involvement over various body parts

Nerve involvement

Minimal or absent

Often present and pronounced

Severity of symptoms


More severe

Transmission risk



Treatment duration



Antibiotics regimen

Usually requires fewer drugs

Requires a combination of multiple antibiotics

Relapse rate




Often easier to diagnose

May be more challenging to diagnose

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What is Paucibacillary Leprosy?

Paucibacillary leprosy is a milder version of the disease. It usually begins with a few (1 to 5) pale, numb skin lesions and may entail early nerve injury. This kind has a low bacterial load and is identified based on clinical indicators rather than identifying the germs.

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Key Features of Paucibacillary Leprosy:

  • Paucibacillary leprosy is distinguished by a modest number of skin lesions, usually two to five patches or macules. These patches might be hypopigmented (lighter than the surrounding skin) or hyperpigmented (darker).
  • Despite its modest skin involvement, PB leprosy can cause peripheral nerve damage early in the disease's progression. This might result in loss of feeling, numbness, or weakening in regions served by the afflicted nerves.
  • Individuals with PB leprosy often have a high cell-mediated immune response. This serves to restrict the growth and spread of Mycobacterium leprae, the organism that causes leprosy.
  • Because of the decreased bacterial burden and robust immune response, PB leprosy has a shorter treatment regimen than multibacillary leprosy. This generally includes six months of multidrug therapy (MDT).

What is Multibacillary Leprosy?

Multibacillary leprosy is more severe. It can produce numerous (more than 5) extensive skin lesions, such as nodules and growths, which frequently affect the face and limbs. Nerve involvement is prevalent. This kind has a high bacterial load, which may be validated with a skin smear test.

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Key Features of Multibacillary Leprosy:

  • Multibacillary leprosy causes multiple skin lesions, frequently more than five patches or macules. These lesions can be infiltrated (thickened) and may contain nodules, papules, or widespread infiltrations.
  • Individuals with MB leprosy have a larger concentration of Mycobacterium leprae bacteria in their bodies. A slit-skin smear test can help detect this.
  • MB leprosy is related with a reduced cell-mediated immune response. This permits the germs to proliferate more easily, causing more widespread sickness.
  • Because of the larger bacterial load and lower immune response, MB leprosy requires a lengthier treatment regimen than PB leprosy. This usually entails MDT for 12 months.

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Similarities Between Paucibacillary and Multibacillary Leprosy

  • Mycobacterium leprae is the bacterium that causes both paucibacillary and multibacillary leprosy.
  • Both varieties of leprosy are persistent and can result in long-term consequences if not treated.
  • Both varieties of leprosy can affect the skin and nerves, although the extent differs.
  • Both forms are diagnosed with a clinical examination, skin biopsy, and, in certain cases, nerve biopsy.
  • Both kinds of leprosy are more common in various parts of the world, notably in the tropical and subtropical zones.

The two primary categories for leprosy treatment regimens are paucibacillary and multibacillary. Paucibacillary leprosy is a milder type of the disease, with fewer than five skin lesions and negative bacterial smears. This signals a reduced bacterial burden and a more robust immunological response. In contrast, multibacillary leprosy is characterised by a more extensive infection, as evidenced by six or more lesions and potentially positive bacterial smears. This indicates a larger bacterial burden and a weakened immune response, requiring a longer and more rigorous treatment regimen.

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What is Paucibacillary Leprosy?

Paucibacillary leprosy is a form of leprosy characterized by the presence of a small number of bacteria in the body, causing few skin lesions.

What is Multibacillary Leprosy?

Multibacillary leprosy is another form of leprosy characterized by a higher bacterial load in the body, resulting in multiple skin lesions and sometimes nerve damage.

What are the similarities between Paucibacillary and Multibacillary Leprosy?

Both forms of leprosy are caused by the bacterium Mycobacterium leprae and are chronic infectious diseases affecting the skin and nerves.

What are the differences between Paucibacillary and Multibacillary Leprosy?

The main difference lies in the bacterial load; paucibacillary leprosy has a lower bacterial count while multibacillary leprosy has a higher count. Additionally, the number of skin lesions and nerve involvement differs between the two forms.

How do symptoms of Paucibacillary and Multibacillary Leprosy differ?

Paucibacillary leprosy typically presents with a few well-defined skin lesions with little to no nerve involvement. Multibacillary leprosy, on the other hand, often presents with numerous skin lesions and may involve nerve damage leading to sensory loss.

What diagnostic tests are used to differentiate between Paucibacillary and Multibacillary Leprosy?

The slit skin smear test, which examines a sample from skin lesions under a microscope, is used to determine the bacterial load and differentiate between the two forms of leprosy.