Mycobacterium Leprae - Clinical manifestation, Lepromatous, Tuberculoid, Borderline, Interminant, Mid-borderline, Leprosy

The cardinal signs of leprosy by Mycobacterium leprae

The cardinal signs of leprosy by Mycobacterium leprae are as follows:

• Hypoesthesia (reduced sense of touch)

• skin lesions

• loss of hair, sweating, and peripheral neuropathy

• the first physical sign of leprosy is usually cutaneous

• the subtype of leprosy often determines the degree of skin involvement

Clinical manifestation/forms of Mycobacterium leprae

On the basis of the Ridley-Joping classification of leprosy, Mycobacterium leprae can manifest as the following clinical manifestation/forms.

Lepromatous leprosy

Lepromatous leprosy is seen mostly in immunocompromised individuals. T-cell immune responses are poor or absent. In this infection, low host resistance is a superficial nodular lesion that ulcerates and gets infected secondarily.

Bacilli invade the mucosa of the eye, nose, mouth, and URT leading to disfigurement. In more infective cases, Bacillemia is common. Patients show widespread areas of infection- lesions are small and many, shiny with no loss of feeling.

Leprosy, caused by Mycobacterium leprae, has a poor prognosis i.e. progress of treatment is low and the Lepromin test is positive. Although large no. of bacteria are found in the body even in normal skin, the micro-organisms multiply mainly in the macrophage cells (histocytes) in the dermis of the skin.

Tuberculoid leprosy

Infected tissues are without feeling or perspiration and are more hypopigmented than the surrounding skin while a few skin lesions may consist of macular anesthetic patches. Also, lesion infectivity is minimal (single) and well-defined skin lesions are observed but bacilli are scanty or absent. Sometimes, a lesion may appear as a flattened area with raised edges.

Tuberculoid leprosy occurs in individuals with normal / High immune responses. As Tcell immune responses are good, high host resistance is observed. Since CMI is adequate, lepronin test is positive. Leprosy infects neural involvement in the early stages which leads to deformities in hands and feet. The affected nerves show marked thickening.

The prognosis caused by Mycobacterium leprae is good for leprosy.

• if 1-5 lesion is present: paucibacillary (1-5 bacilli)

• if more than 5 lesion: Multibacillary (>5 bacilli)

Borderline or dimorphous leprosy

Borderline or dimorphous leprosy has the characteristics of both tuberculoid and lepromatous types. This form may remain the same or might shift to any type and may occur depending upon the host's immune response.

The skin lesions are few, asymptomatic, and with nearly complete anesthesia.

Interminant leprosy

Interminant leprosy is a type of lesion which do not show the characteristics of tuberculoid and might heal spontaneously. However, the lesion caused by Mycobacterium leprae might shift to a tuberculoid or lepromatous type

Mid-borderline leprosy

The skin lesions of Mid-borderline leprosy caused by Mycobacterium leprae consist of numerous unequally shaped plaques that are less well-defined than in tuberculoid types and are distributed symmetrically. Anesthesia is moderate and the disease can remain in this stage and can improve or worsen.

Diagnosis of Mycobacterium leprae

Diagnosis of Mycobacterium leprae is based on one or more of 3 signs:

1. Hypopigmentation or erythematous macules with sensory loss

2. Thickened peripheral nerves

3. A positive acid-alcohol fast smear