Interstitial Lung Disease (ILD)

Exam Cram

• Interstitial lung disease is a collection of 100+ lung diseases associated with significant mortality through developing pulmonary hypertension, 

• Common types: idiopathic (IPF), medication induced, autoimmune and exposure (asbestosis & silicosis)

• Spirometry: restrictive lung disease (reduced FVC and FEV-1)

• Management: endothelin receptor antagonists

Defining ILD

Definitions

• ILD: Interstitial Lung Disease, comprises of around 100 lung diseases.

• Pulmonary Fibrosis: non specific name, often referring to idiopathic but could be related to any cause of pulmonary fibrosis. 

• IPF: idiopathic pulmonary fibrosis, the commonest cause of ILD  and of pulmonary fibrosis. 

5 core types of ILD

1. Exposure/ occupations: asbestosis, silicosis, hypersensitivity pneumonitis (birds- pigeons, mould)

2. Medication related (see below)

3. Connective tissue disorders: Systemic Lupus Erythematous , Dermato/polymyositis , Rheumatoid Arthritis, Systemic Sclerosis 

4. Sarcoidosis 

5. Idiopathic

Further types

• Histiocytosis X

• Chronic eosinophilic pneumonia

• Goodpasture's Disease 

• GPA 

Cause of drug induced fibrosis (NASSA)

• Nitrofurantoin

• Sulphonamides

• Sulfasalazine

• Amphotericin B

• Chemotherapy- bleomycin

• Radiotherapy

• Tamoxifen

Amiodarone- commonly cited but actually drug induced pneumonitis which usually resolved on cessation of drug without steroids. 

Methotrexate also causes pneumonitis that mimics ILD. 

ILD Outline

Background

• Core PACES presentation

Assessment

History

• Progressive sob, reduced exercise tolerance

• Dry cough

Examination

• Finger clubbing

• Bi-basal fine inspiratory crackles

Investigations

• CXR

• High resolution CT: honeycombining (fibrosis), ground glass (alveolitis)

• Spirometry: restrictive pattern, reduced transfer factor

Diagnosis

Diagnostic criteria: presentation, HRCT interstitial pattern, PFTs +- biopsy

Differentials: COPD, CHF, Aspergillosis 

Classification: 

1. Aetiology- as per subtype

2. Severity markers

Management: 

Assessment

1. Severity 

   • ECHO: Pulmonary Hypertension

   • PFTs: 

     • TLCO: reduced (marker of disease severity)

     • Transfer factor: reduced

   • ABG: PO2 ?LTOT

   • High resolution CT

2. Underlying Cause

   • Autoimmune- ANA, ANCA

   • Exposure history- abestos, silicon, pigeons

   • Medication- amiodarone, radiotherapy

   • Family history

   • Allergy screen: IgE to allergens, aspergillosis serology

   • Biopsy- e.g. sarcoidosis

Acute exacerbation

• Consider steroids if inflammatory subtype

• Antibiotics if unwell or signs of bacterial infection

Chronic: 

• MDT

  • Referral to specialist centre: Respiratory consultant ILD specialty (FVC < 80%)

  • Respiratory nurses, PT- chest physio, OT, dietician, psychologist, Advance directives, Transplant surgeons

• Lifestyle- smoking cessation, pulmonary rehab

• Medical- antifibroitic agents: Nintedanib, Pirfenidone; low dose morphine (symptom), treat underlying cause

• Surgical- rarely unilateral or bilateral lung transplants

Deeper Dive

Upper vs Lower Fibrosis

Upper Lobe Fibrosis

• Ankylosing spondylitis

• Tuberculosis

• Sarcoidosis

• Hypersensitivity pneumonitis (previously called EAA- Extrinsic Allergic Alveolitis)

• Silicosis

• ABPA

• Post radiotherapy

Lower Lobe Fibrosis

• Idiopathic

• Rheumatoid Arthritis

• Systemic Sclerosis (Scleroderma)

• SLE

• Post radiotherapy

Pulmonary Hypertension 

Refers to increased pressures in the pulmonary arterial tree from the right ventricle. This is comparable to Hypertension which refers to elevated pressures in the systemic arterial system from the left ventricle. 

Pulmonary hypertension is common in lung diseases because the heart has to push harder. Therefore pulmonary HTN is common in ILD, but a distinct disease.

Treatment

• Repeat pulmonary function test 6m ?start

• FVC < 40% - antifibrotics

• Consider lung transplant if no contraindication

Prognosis

ILD- 2-3 years, NSIP- non specific interstitial pneumonia has a better prognosis. 

Severity markers: 

• Pulmonary HTN

• Frailty, older age, low exercise tolerance, exertional desaturation

• Declining PFT

• Extensive radiographic disease

Hypersensitivity pneumonitis

Background

• Type of ILD

• Occupation exposure, e.g. farmwork- farmer's lung or bird fancier's lung

• May not cause finger clubbing

Diagnosis

• History: exposure + lethargy, SoB, wheeze, chest pains

• Examination: upper lobe crackles

• Work up

  • Basic: CXR, ECG, baseline bloods (FBC, U&Es, CRP, LFTs)

  • HRCT

  • PFT

  • IgE- allergens, IgE aspergillosis

  • Respiratory referral

Management

Removal of allergen. 

References

1. Types (2017) Stanford Health Care. Available at: https://stanfordhealthcare.org/medical-conditions/chest-lungs-and-airways/interstitial-lung-disease/types.html (Accessed: 07 October 2024).

2. https://www.mayoclinic.org/diseases-conditions/interstitial-lung-disease/diagnosis-treatment/drc-20353113

3. https://www.nhlbi.nih.gov/health/interstitial-lung-diseases/diagnosis

Written in 2024