# Histoid and Pure Neuritic Leprosy

> Histoid and pure neuritic leprosy for NEET-PG Dermatology covers their clinical and histological features and the diagnostic challenges they pose.

- Canonical URL: https://prepelephant.com/topics/neet-pg/dermatology/histoid-and-pure-neuritic-leprosy
- Exam / course: NEET-PG · Subject: Dermatology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-15
- Last updated: 2026-10-15
- Reference basis: Rook's Textbook of Dermatology; IADVL Textbook of Dermatology; National Leprosy Eradication Programme guidelines
- How to cite: "Histoid and Pure Neuritic Leprosy", PrepElephant, https://prepelephant.com/topics/neet-pg/dermatology/histoid-and-pure-neuritic-leprosy

## Direct answer

Histoid leprosy and pure neuritic leprosy are two uncommon variants that break the usual skin-based pattern of the disease. Histoid leprosy produces firm, dome-shaped, shiny papules and nodules made of spindle-shaped histiocytes that are packed with bacilli, and it classically appears in relapse. Pure neuritic leprosy involves nerves without any skin lesions, so the diagnosis depends on nerve examination and, often, nerve biopsy.

## What you must remember

- **Histoid leprosy:** firm, dome-shaped, shiny, skin-coloured papules and nodules, often on the extensor surfaces, with little sensory loss.
- **Histology of histoid lesions:** a dense dermal proliferation of spindle-shaped histiocytes with abundant bacilli.
- **Setting:** histoid lesions are seen mainly in relapse of lepromatous disease, including after dapsone monotherapy or with drug-resistant bacilli.
- **Pure neuritic leprosy:** nerve thickening and sensory or motor loss without any skin lesion.
- **Diagnosis of pure neuritic leprosy:** clinical nerve examination, supported by nerve biopsy, since there is no skin lesion to sample.
- **Diagnostic challenge:** histoid papules can mimic dermatofibroma or neurofibroma.
- **Skin smear:** usually strongly positive in histoid lesions, whereas it is scanty or negative in pure neuritic disease.
- **Treatment:** histoid leprosy needs multidrug therapy chosen for the relapse or resistance pattern, and the regimen for pure neuritic disease varies across guidelines.

## A stepwise approach to the two variants

Firm shiny papules in a relapsed lepromatous patient and a thickened nerve with no skin lesion point to two different variants. The steps below separate them and avoid the common mistake of treating both as ordinary disease.

1. **Suspect the variant:** Firm shiny papules in a relapsed lepromatous patient suggest histoid leprosy, while a painful thickened nerve with sensory loss and no skin lesions suggests pure neuritic leprosy.
2. **Take a skin smear:** A slit skin smear shows heavy solid-staining bacilli in histoid lesions, whereas it is often scanty or negative in pure neuritic disease.
3. **Biopsy the lesion or nerve:** A skin biopsy confirms histoid leprosy, while a nerve biopsy is needed when no skin lesion is present.
4. **Check the treatment history:** Ask about previous multidrug therapy, dapsone monotherapy and adherence, since relapse and drug resistance change the choice of regimen.
5. **Exclude mimics:** Histoid papules can resemble dermatofibroma or neurofibroma, and an enlarged nerve can resemble other neuropathies.
6. **Plan the regimen:** Histoid leprosy is treated with a multidrug regimen tailored to the relapse or resistance pattern, and the classification of pure neuritic disease should follow current national guidelines.
7. **Follow up the nerves:** Repeat nerve function checks, because neuritic involvement can progress or leave damage even after treatment.

## Where the exam tries to catch you

Most traps involve confusing these variants with tumours or with ordinary neuropathies.

- **Trap:** calling histoid papules a benign dermatofibroma — **Correct:** histoid lesions are firm and shiny but rich in bacilli, so a biopsy with acid-fast staining is needed.
- **Trap:** expecting a skin smear to be positive in pure neuritic leprosy — **Correct:** with no skin lesions the smear is often negative, so nerve examination and biopsy carry the diagnosis.
- **Trap:** treating an isolated thickened nerve as a routine neuropathy — **Correct:** in an endemic setting, a thickened painful nerve with sensory loss should prompt a leprosy workup.
- **Trap:** assuming histoid leprosy is always a new infection — **Correct:** it classically arises in relapse, so the treatment history and adherence matter.

## Frequently asked questions

### What is histoid leprosy?
Histoid leprosy is a variant of lepromatous leprosy in which firm, dome-shaped, shiny papules and nodules develop on the skin. The lesions are made of spindle-shaped histiocytes rich in bacilli and classically appear in relapse.

### What is pure neuritic leprosy and how is it diagnosed?
Pure neuritic leprosy is nerve involvement without any skin lesion, presenting as nerve thickening with sensory or motor loss. It is diagnosed clinically and often confirmed by nerve biopsy, since there is no skin lesion to examine.

### Which conditions mimic histoid leprosy?
Histoid leprosy can resemble dermatofibroma, neurofibroma and other dermal tumours because its papules are firm and dome-shaped. A skin biopsy with acid-fast staining distinguishes histoid leprosy from these benign tumours.

### Why is pure neuritic leprosy a diagnostic challenge?
Pure neuritic leprosy lacks the skin lesions that normally guide the diagnosis in leprosy. The patient presents with nerve thickening or weakness, so it is easily mistaken for other neuropathies without nerve examination or biopsy.

### Is histoid leprosy treated differently from classic lepromatous leprosy?
Histoid leprosy is treated with a multidrug regimen, but the choice depends on relapse and any drug resistance. Clinicians review the previous treatment and adherence before deciding on the regimen for histoid leprosy.