Sarcoidosis

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1- Definition & Types

2- Causes (Aetiology)

3- Pathophysiology

4- Clinical Features & Examination

5- Investigations

6- Management

7- Complications

8- Core Concepts

Definition & Types

Sarcoidosis is a multisystem granulomatous disease of unknown cause, characterized histologically by non-caseating granulomas.

90% of cases involve the lungs, but any organ may be affected.

Types (Based on presentation or organ involvement):

Pulmonary sarcoidosis (most common)

Löfgren’s syndrome (acute form with erythema nodosum, arthralgia, BHL)

Cardiac, neurological, ocular, hepatic, renal, and cutaneous sarcoidosis

Sarcoidosis with central fibrosis of granulomas © image from Wikimedia Commons

Causes (Aetiology)

Unknown, but likely due to:

  • Genetic predisposition (HLA class II alleles)

  • Environmental triggers:

    • Mycobacteria, propionibacteria, and viruses (theory)

  • More common in cold climates, and more severe in West Indian and Asian populations

  • Less frequent in smokers

Pathophysiology

  • Environmental antigen stimulates the immune system in a genetically susceptible person

  • T-cell activation → cytokine release

  • Granuloma formation: compact clusters of epithelioid cells, macrophages, and multinucleated giant cells, without caseation (non-caseating)

  • Organ infiltration → dysfunction (esp. lungs, lymph nodes, skin, eyes)

Clinical Features & Examination

Highly variable! Often called the “great mimicker.”

– Systemic Presentations:

  • Asymptomatic (~30%, abnormal CXR or LFTs)

  • Constitutional: fever, fatigue, weight loss

  • Löfgren’s syndrome:

    • Erythema nodosum

    • Bilateral hilar lymphadenopathy (BHL)

    • Arthralgia

    • Uveitis

    • Usually self-limiting

– Respiratory:

  • Dry cough, exertional dyspnoea, chest discomfort

  • CXR: BHL ± infiltrates

  • Auscultation often unremarkable

– Ocular (5–10%):

  • Anterior uveitis (can lead to blindness)

– Skin:

  • Erythema nodosum

  • Lupus pernio (chronic violaceous plaques on nose/face)

– Neuro:

  • Cranial nerve palsies (especially CN VII), meningitis, DI

– Cardiac:

  • Arrhythmias, heart block, sudden death

Other:

  • Superficial lymphadenopathy

  • Hypercalcaemia, nephrocalcinosis

  • Liver, spleen, bone, parotid gland involvement

© image from Wikimedia Commons

Investigations

Blood tests:

  • Lymphopenia

  • Raised ACE (non-specific marker of disease activity)

  • Hypercalcaemia / hypercalciuria

  • Mildly raised LFTs

🩻 Imaging (Box 17.73 – Radiographic staging):

  • Stage I: BHL only

  • Stage II: BHL + pulmonary infiltrates

  • Stage III: Infiltrates without BHL

  • Stage IV: Pulmonary fibrosis

🔬 Diagnostic procedures:

  • Bronchoscopy with transbronchial biopsy: non-caseating granulomas

  • Bronchoalveolar lavage: ↑ CD4:CD8 ratio

  • PET-CT: to assess systemic involvement

  • HRCT: perilymphatic nodules, reticulonodular pattern

  • Lung function: restrictive defect ± impaired gas exchange

© image from Wikimedia Commons

Management

  • Observation if asymptomatic or mild disease (many resolve spontaneously)

  • Corticosteroids: first-line for symptomatic or organ-threatening disease

  • Immunosuppressants (e.g. methotrexate, azathioprine): if steroid-resistant

  • Organ-specific therapy (e.g. pacemaker for cardiac involvement)

  • Calcium monitoring + hydration to prevent nephrocalcinosis

Complications

  • Pulmonary fibrosis

  • Pulmonary hypertension

  • Cor pulmonale

  • Bronchiectasis

  • Aspergilloma

  • Blindness (from uveitis)

  • Cardiac arrhythmias → sudden death

  • Hypercalcaemia-related kidney damage

Core Concepts

  • Non-caseating granulomas = diagnostic hallmark

  • BHL on CXR in asymptomatic person → Think sarcoid

  • Löfgren’s syndrome = good prognosis

  • Always check calcium, ACE, LFTs, and consider HRCT

  • Steroids = mainstay treatment, but not always needed

  • Screen for cardiac and ocular involvement even if asymptomatic

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