Sarcoidosis
An inflammatory disease where tiny collections of immune cells (granulomas) grow in the lungs, lymph nodes, and other organs, causing coughing and shortness of breath.
Emergency Management: Complete heart block (3rd degree AV block) due to granuloma in the bundle of His. Presents as severe bradycardia and syncope. Requires emergent transcutaneous pacing and subsequent permanent pacemaker placement.
Sarcoidosis is a multisystem granulomatous disorder of unknown etiology, characterized by the formation of noncaseating granulomas in affected organs. It most commonly affects the lungs and intrathoracic lymph nodes, but can involve the skin, eyes, liver, and heart.
Detailed Overview
The hallmark of sarcoidosis is an exaggerated CD4+ T-cell mediated immune response to an unidentified antigen, leading to granuloma formation. In the lungs, this causes restrictive lung disease and fibrosis. Symptoms vary widely from asymptomatic incidental findings on chest X-rays (hilar adenopathy) to severe, progressive multi-organ failure. The clinical course is highly variable; roughly two-thirds of patients experience spontaneous remission, while one-third develop chronic, progressive disease.
Epidemiology & Demographics
Highest prevalence in African Americans (up to 35 per 100,000) and Northern European/Scandinavian populations. Typically presents in adults 20-40 years old. Slightly more common in women, who tend to have more severe cutaneous and ocular involvement.
Etiological Mechanism
The exact cause is unknown. It is hypothesized to be an aberrant immune response to an environmental, occupational, or infectious antigen (e.g., Propionibacterium acnes, mycobacterial antigens, or beryllium) in genetically susceptible individuals (HLA-DRB1 alleles).
Primary Causes
Idiopathic. Triggered by unknown airborne antigens inducing a Th1-mediated immune response in the lungs.
An unknown antigen is processed by alveolar macrophages and presented to CD4+ T-helper cells. This triggers a massive Th1 response, secreting IL-2, IFN-gamma, and TNF-alpha. These cytokines recruit and activate more macrophages, which aggregate and transform into epithelioid cells and multinucleated giant cells, forming noncaseating granulomas. These granulomas displace normal tissue, causing organ dysfunction. Activated macrophages within the granulomas also express 1-alpha-hydroxylase, an enzyme that converts 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D, leading to hypercalcemia. Fibroblasts may be recruited, causing irreversible pulmonary fibrosis.
Diagnostic Criteria & Guidelines
Requires three elements: 1) Compatible clinical and radiographic presentation, 2) Histological evidence of noncaseating granulomas (via bronchoscopy with transbronchial biopsy or biopsy of skin/lymph node), and 3) Exclusion of other granulomatous diseases (negative AFB stains for TB, negative fungal cultures).
For asymptomatic Stage I disease: No treatment, observation only. For symptomatic pulmonary disease or declining lung function: Systemic corticosteroids. Prednisone 20-40 mg PO daily, tapered over 6-12 months.
Second-Line & Adjunctive Therapy
For steroid-refractory disease, steroid-sparing agents are used: Methotrexate 10-15 mg PO weekly, Azathioprine, or Mycophenolate mofetil. Third-line for severe/refractory disease uses TNF-alpha inhibitors like Infliximab 3-5 mg/kg IV infusion.
Surgical & Procedural Management
Lung transplantation for end-stage fibrotic lung disease (Stage IV). Pacemaker/ICD placement is critical for patients with cardiac sarcoidosis presenting with conduction blocks or arrhythmias.
Patient Counseling & Advice
Inform patients that the disease often goes away on its own without treatment. Annual eye exams by an ophthalmologist are mandatory to catch asymptomatic uveitis before it causes blindness. Report any new palpitations or fainting spells immediately, as they may indicate cardiac involvement.
Follow-Up & Monitoring Schedule
Pulmonary function tests (Spirometry and DLCO) and Chest X-ray every 3-6 months. Annual ECG to screen for heart block. Routine basic metabolic panel to monitor serum calcium and creatinine.
Preventive Strategies
No known preventive measures as the etiology remains unknown.
Generally good; up to 60-70% achieve spontaneous remission within 2-5 years. However, 10-20% suffer permanent lung damage. Mortality is 1-5%, primarily from advanced pulmonary fibrosis, cardiac arrhythmias, or neurologic involvement.