top of page
Search

Interstitial Lung Disease (ILD) Patterns: Criteria & Principles — MRCP Part 1

TL;DR

For MRCP Part 1, ILD questions reward rapid pattern recognition on HRCT combined with clinical context. Focus on five core patterns (UIP, NSIP, HP, sarcoidosis, organising pneumonia), their defining criteria, and classic exclusions. Mastering these differences reliably converts stems into marks.


Why ILD patterns matter in MRCP Part 1

Interstitial lung disease is a high-yield respiratory topic because it tests integration: imaging, pathology, physiology, and systemic disease. The exam does not expect subspecialty nuance; instead, it expects you to identify a pattern, match it to the right clinical setting, and avoid common look-alike traps.

You’ll typically see: age, smoking status, exposures, a brief HRCT description, and one or two systemic clues. If you can anchor on pattern first, the answer often becomes obvious.


Scope & exam principles

  • Pattern > cause: Recognise the radiological pattern before thinking of aetiology.

  • Distribution matters: Upper vs lower zones, subpleural vs central.

  • Key exclusions score marks: Some features actively rule out certain patterns.

  • Physiology supports imaging: Restriction and reduced DLCO are common across fibrotic ILDs.

The 5 most tested ILD patterns (with criteria)

1) Usual Interstitial Pneumonia (UIP)

  • Typical patient: Older adult, often with smoking history

  • HRCT: Basal, subpleural fibrosis with honeycombing ± traction bronchiectasis

  • Key association: Idiopathic pulmonary fibrosis (IPF)

  • Exam pearl: Honeycombing with minimal ground glass strongly favours UIP

2) Non-Specific Interstitial Pneumonia (NSIP)

  • Typical patient: Younger than UIP, often female

  • HRCT: Symmetrical ground-glass opacification, fine reticulation, possible subpleural sparing

  • Key association: Connective tissue disease (especially systemic sclerosis)

  • Exam pearl: Better prognosis than UIP

3) Hypersensitivity Pneumonitis (HP)

  • Typical patient: Any age, clear exposure history (birds, moulds)

  • HRCT: Centrilobular nodules, mosaic attenuation, air-trapping

  • Distribution: Upper or mid-zones

  • Exam pearl: Think small airways + exposure

4) Sarcoidosis

  • Typical patient: Young or middle-aged adult

  • HRCT: Perilymphatic nodules, upper-lobe fibrosis in advanced disease

  • Key association: Bilateral hilar lymphadenopathy, extrapulmonary signs

  • Exam pearl: Upper-zone disease with nodes = sarcoid until proven otherwise

5) Organising Pneumonia (OP)

  • Typical patient: Post-infection, drug-related, or autoimmune disease

  • HRCT: Patchy peripheral consolidation, sometimes migratory

  • Key feature: Steroid responsive

  • Exam pearl: Consolidation is not always infection


High-yield differences at a glance

Feature

UIP

NSIP

HP

Sarcoidosis

OP

Age

Older

Younger

Any

Young

Any

Distribution

Basal, subpleural

Diffuse

Upper/mid

Upper

Peripheral

Dominant CT sign

Honeycombing

Ground glass

Air-trapping

Perilymphatic nodules

Consolidation

Prognosis

Poor

Better

Variable

Variable

Good

Typical association

IPF

CTD

Antigen exposure

Systemic disease

Drugs/infection

10 high-yield points examiners love

  1. Honeycombing is diagnostic for UIP in the right context.

  2. Predominant ground glass favours NSIP or OP, not UIP.

  3. Upper-lobe disease with lymphadenopathy suggests sarcoidosis.

  4. Mosaic attenuation plus exposure history points to HP.

  5. Traction bronchiectasis supports fibrotic ILD.

  6. Smoking history increases the likelihood of UIP.

  7. CTD features push you towards NSIP.

  8. Reversible symptoms and imaging favour OP or HP.

  9. Subpleural sparing argues against UIP.

  10. Reduced DLCO is common across fibrotic ILDs.

A postgraduate medical student revising respiratory notes on a laptop with CT images or textbooks open.

Mini-MCQ (exam style)

A 68-year-old ex-smoker presents with progressive exertional dyspnoea. HRCT shows basal subpleural fibrosis with honeycombing and traction bronchiectasis. There is minimal ground-glass change. What is the most likely ILD pattern?

A. NSIPB. Organising pneumoniaC. UIPD. Hypersensitivity pneumonitisE. Sarcoidosis

Correct answer: C — UIP

Explanation: The combination of age, smoking history, basal subpleural fibrosis, and honeycombing is classic for UIP. Ground-glass-predominant patterns (NSIP, OP), exposure-related disease (HP), and upper-lobe nodular disease (sarcoid) do not fit this stem.

You can practise similar questions in the Crack Medicine Qbank:https://crackmedicine.com/qbank/


Common pitfalls (5 traps)

  • Mistaking ground glass for honeycombing

  • Ignoring lobar distribution

  • Forgetting to ask about antigen exposure

  • Over-diagnosing UIP in young CTD patients

  • Assuming all consolidation equals infection


Practical study-tip checklist

  • Learn patterns first, causes second

  • Link each pattern to one defining CT sign

  • Always check age, smoking, and exposure history

  • Revise HRCT alongside pulmonary function tests

  • Test recognition speed using mock examshttps://crackmedicine.com/mock-tests/


FAQs

Which ILD pattern is most common in MRCP Part 1?

UIP and NSIP are the most frequently tested, usually via classic HRCT descriptions.

How do I quickly distinguish UIP from NSIP?

Honeycombing with basal subpleural fibrosis suggests UIP; symmetrical ground glass suggests NSIP.

Is lung biopsy required to diagnose UIP in exams?

No. A classic UIP pattern on HRCT is sufficient for exam purposes.

Which ILD responds best to steroids?

Organising pneumonia shows the most consistent steroid response.


Ready to start?

Ready to turn ILD pattern recognition into guaranteed marks?

👉 Revise smarter for MRCP Part 1 with structured notes, high-yield MCQs, and exam-level mocks from Crack Medicine:


Sources

 
 
 

Comments

bottom of page