Subtitle: Complete lepromatous leprosy histopathology with Grenz zone, Fite stain, globi, BI grading and exam MCQs

Category: Skin Pathology / Infectious Pathology
Last Updated: 2026
Read Time: 20 minutes

At a Glance

• Multibacillary Hansen disease
• Diffuse foamy macrophage dermal replacement
• Very high bacillary index with globi

Table of contents

• What is Lepromatous Leprosy?
• Lepromatous Leprosy Histopathology
• Grenz Zone and Diffuse Dermal Infiltration
• Cutaneous Nerve Involvement
• Fite Stain Demonstrating Bacillary Load
• Globi Formation
• Hair Follicle Involvement
• Sebaceous Gland Involvement
• Adnexal Structure Involvement
• Classification of LePromatous Leprosy
• Bacteriological Index
• Lepra Reactions
• High-Yield MCQs
• Exam Pearl
• Key Takeaway
• View virtual slide
• View Video Explanation
• Recommended Learning

What is Lepromatous Leprosy?

Lepromatous leprosy is the multibacillary pole of Hansen disease caused by Mycobacterium leprae. It is characterized by defective cell-mediated immunity, diffuse dermal infiltration by macrophages, widespread nerve involvement, and massive acid-fast bacillary load.

Core Lepromatous Leprosy Histopathology

Lepromatous leprosy histopathology shows preserved epidermis, a Grenz zone, diffuse sheets of foamy macrophages replacing dermis, adnexal and nerve infiltration, and abundant acid-fast bacilli forming globi.

Grenz Zone and Diffuse Dermal Infiltration

• Grenz zone indicates failure of epidermal invasion by lepra macrophages.
• Distinguishes lepromatous from tuberculoid leprosy.
• Associated with symmetrical diffuse lesions.

Cutaneous Nerve Involvement

• Schwann cell invasion causes glove-and-stocking anesthesia.
• Persistent infiltration leads to muscle wasting.
• Predisposes to trophic ulcer formation.

Fite Stain Demonstrating Bacillary Load

• Preserves lipid-rich mycobacterial walls.
• High bacillary load correlates with infectivity.
• Guides MDT duration.

Globi Formation

• Seen only in lepromatous pole.
• Indicates massive intracellular replication.
• Predicts high relapse risk.

Hair Follicle Involvement

• Causes madarosis and alopecia.
• Indicates hematogenous spread.
• Seen in advanced multibacillary disease.

Sebaceous Gland Involvement

• Loss of sebum causes xerosis.
• Leads to fissuring and secondary infection.
• Supports diagnosis of multibacillary disease.

Adnexal Structure Involvement

• Sweat gland destruction causes anhidrosis.
• Produces thermal dysregulation.
• Contributes to trophic ulcer formation.

How is Lepromatous Leprosy Classified and Why It Matters?

System	Lepromatous Category
Ridley–Jopling	LL
WHO Operational	Multibacillary

All lepromatous leprosy cases are multibacillary, determining MDT duration and infectivity reporting

What is the Bacteriological Index and How is it Interpreted?

BI	Meaning
1+	Occasional bacilli
4+–6+	Massive bacillary load with globi

Lepromatous leprosy usually shows BI ≥4+, correlating with relapse risk and treatment duration.

What are Lepra Reactions and Their Histopathology?

Reaction	Histopathology
Type 1	Dermal edema, emerging granulomas
Type 2 (ENL)	Neutrophilic vasculitis, panniculitis

ENL is strongly associated with lepromatous disease.

High – yield MCQS

Exam Pearl

Grenz zone + foamy macrophages + Fite-positive globi = Lepromatous leprosy histopathology

View the virtual slide

Watch the video

Key Takeaway

LePromatous leprosy histopathology shows diffuse macrophage replacement of dermis, widespread adnexal and nerve involvement, and extremely high bacillary index.

Recommended learning