ii. Lepromatous Leprosy

Lepromatous Leprosy

Results when the host is anergic and lacks T-cell mediated immune response

Key Questions & Answers 

1. Name the histological variants

Based on host cellular immune response leprosy can be classified as 

1. Tuberculoid Leprosy (TT) – in which case the host mounts T-cell, mediated immune response

2. Borderline Tuberculoid leprosy (BT)

3. Borderline Borderline leprosy (BB)

4. Borderline Lepromatous leprosy (BL)

5. Lepromatous Leprosy (LL)- in which case the Host is anergic and lacks T-cell mediated immune response

2.Write about lepra reaction

Lepra reactions are acute inflammatory episodes that may be seen in patients with leprosy. These reactions may occur at any time before, during, or after treatment for the infection 

Type I Lepra reaction

Type 1 reactions result due to changes in cell-mediated immunity (CMI) to the infectious agent Mycobacterium leprae. It may occur in any subtype of leprosy, but it is frequently seen in patients with borderline leprosy. 

Patients with Type 1 reaction present with increased erythema, edema and warmth of preexisting cutaneous plaques and nodules. They often present with edema of hands and feet, ulcerations of preexisting lesions and formation of new plaques. Additionally, there may be swelling and tenderness of peripheral nerves and loss of neurologic function. Systemic symptoms are uncommon. This reaction may be seen after pregnancy, with immunosuppressive treatment or in patients co-infected with HIV within months of starting antiretroviral therapy 

Type II reaction/ Erythema nodosum leprosum (ENL)

Common in LL, Less frequent in BL

Type 2 Lepra reactions (erythema nodosum leprosum), are associated with circulation and tissue deposition of immune complexes. They are an antibody response or immune complex response to M. leprae antigenic determinants which occur in multibacillary leprosy with heavy load of bacilli

It may occur in the early stages of treatment and even after completion of the treatment. It occurs when large numbers of leprosy bacilli are killed, followed by release of their antigens. The antigens from the dead bacilli provoke an arthus type allergic reaction producing antigen antibody immune complex reaction in the presence of complement system. Immune complexes are precipitated in the tissues like the skin, eyes, joints, lymph nodes, kidneys, liver, spleen, bone marrow, endocardium and testes as well as in the circulation 

Type 2 reactions exhibit typical signs of erythema nodosum that presents as red, firm, painful, tender cutaneous and subcutaneous nodules and plaques of variable size that appear in crops. Lesions are usually multiple, tend to be distributed bilaterally and symmetrically. They are often seen to involve the cooler parts of the skin (on face and outer surface of limbs and less frequently on the trunk) and do not last longer than 2 or 3 days. The patients present with fever, malaise, arthralgia, leukocytosis and oedema of face, hands and feet. There could be involvement of nerves and other vital organs like kidneys, liver, bone marrow and endocardium.

Microscopically there is 

• acute inflammation

• necrotizing vasculitis and 

• ulceration 

Type III reaction/ Lucio reaction

Occurs in diffuse LL

Seen in patients without or inadequate treatment, they manifest as tender nodules with ulceration, bulla formation, hemorrhagic irregular plaques and necrotic areas. Microscopically they present as

• endothelial proliferation with obliteration of lumen

• thrombosis of vessels in dermis

• hemorrhagic infarcts

3.Which are the special stains used to demonstrate lepra bacilli?

Modified Ziehl-Neelsen stain and Fite farraco stain are the special stains used to demonstrate the lepra bacilli. (About 1000 bacilli/ cu mm of tissue should be present to detect 1 bacillus in a section.)