# Scrofuloderma and Tuberculosis Verrucosa Cutis

> Scrofuloderma and tuberculosis verrucosa cutis for NEET-PG Dermatology: contiguous versus inoculation spread, cold abscess with sinuses and prosector's wart.

- Canonical URL: https://prepelephant.com/topics/neet-pg/dermatology/scrofuloderma-and-tb-verrucosa-cutis
- Exam / course: NEET-PG · Subject: Dermatology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Rook's Textbook of Dermatology; IADVL Textbook of Dermatology; Harrison's Principles of Internal Medicine
- How to cite: "Scrofuloderma and Tuberculosis Verrucosa Cutis", PrepElephant, https://prepelephant.com/topics/neet-pg/dermatology/scrofuloderma-and-tb-verrucosa-cutis

## Direct answer

Scrofuloderma is cutaneous tuberculosis arising by contiguous spread from an underlying focus, such as a tuberculous node, bone or joint, producing a cold abscess that discharges through sinuses. Tuberculosis verrucosa cutis is a warty plaque caused by direct inoculation of Mycobacterium tuberculosis into the skin, most often in people who handle infected material. The route of entry, contiguous or inoculated, separates the two.

## What you must remember

- **Scrofuloderma route:** contiguous spread from an underlying focus, most often a cervical lymph node, bone, joint or epididymis.
- **Scrofuloderma morphology:** a painless cold abscess with violaceous overlying skin, undermined edges and sinuses discharging pus or caseous material.
- **Collar-stud abscess:** a subcutaneous abscess with a narrow neck to the skin, a classic feature of tuberculous lymphadenitis and scrofuloderma.
- **Scrofuloderma sites:** the neck, axilla and groin, following the lymph node chains.
- **TB verrucosa cutis route:** direct inoculation through minor injury, classically in pathologists, butchers and healthcare workers, giving the name prosector's wart.
- **TB verrucosa cutis morphology:** verrucous, warty plaques, usually on the hands, fingers and knees, with a granulomatous base and few bacilli.
- **Histology:** caseating granulomas in scrofuloderma, while TB verrucosa cutis shows granulomas with pseudoepitheliomatous hyperplasia.
- **Treatment:** standard antitubercular therapy under NTEP, with an evaluation for the underlying source and HIV; simple incision of a cold abscess is avoided because sinuses often persist.

## Contiguous spread versus direct inoculation

The two forms differ mainly in how the bacillus reached the skin, and the table sets out the features that follow from that route. Candidates should start with the route, because the morphology and site then fall into place.

| Feature | Scrofuloderma | TB verrucosa cutis |
|---|---|---|
| Route | Contiguous spread from a deep focus | Direct inoculation of the skin |
| Typical lesion | Cold abscess with sinuses | Warty, verrucous plaque |
| Typical sites | Neck, axilla, groin | Hands, fingers, knees |
| Bacillary load | Relatively abundant | Few bacilli |
| Histology | Caseating granulomas | Granulomas with pseudoepitheliomatous hyperplasia |

A sinus draining over a tender cervical node points to scrofuloderma, whereas a warty plaque on the hand of a pathologist points to TB verrucosa cutis. The same route logic explains the histology, since a deep caseating focus produces caseous necrosis, whereas a skin-limited inoculation lesion produces a more proliferative, warty response. Identifying the underlying focus is essential, because treating only the skin leaves the source untreated.

## Where the exam catches students

Most traps involve treating the skin lesion in isolation or misreading the route.

- **Trap:** diagnosing scrofuloderma from the abscess alone — **Correct:** contiguous spread defines the condition, so the source, such as a node, bone or joint, must be sought.
- **Trap:** treating a cold abscess by incision alone — **Correct:** incision often converts it into a chronic sinus, so antitubercular therapy is the primary treatment.
- **Trap:** calling a warty hand lesion a viral wart without asking about occupational exposure — **Correct:** TB verrucosa cutis follows inoculation, so exposure history and a tuberculin test help distinguish it from verruca.
- **Trap:** expecting many bacilli in TB verrucosa cutis — **Correct:** bacilli are few, so the diagnosis rests on histology and clinical context rather than smear positivity.

## Frequently asked questions

### What is a collar-stud abscess?
A collar-stud abscess is a subcutaneous abscess with a narrow neck connecting it to the skin, and it is classically associated with tuberculous lymphadenitis and scrofuloderma. Its shape reflects pus tracking up through a narrow channel from the deeper focus.

### How does scrofuloderma differ from tuberculosis verrucosa cutis?
Scrofuloderma arises by contiguous spread from an underlying focus such as a lymph node, bone or joint, producing a cold abscess and sinuses. Tuberculosis verrucosa cutis results from direct inoculation of the skin, producing a warty plaque with few bacilli.

### Why should a scrofuloderma cold abscess not be simply incised?
Simple incision of a cold abscess in scrofuloderma often leaves a chronic sinus that fails to heal. Antitubercular therapy is therefore the primary treatment, with surgery reserved for specific complications.

### Who is at risk of tuberculosis verrucosa cutis?
TB verrucosa cutis is classically seen in pathologists, butchers, healthcare workers and others who handle infected material, which is why it is also called prosector's wart. The lesion typically develops on the hands and fingers after inoculation through a minor skin injury.