Sarcoidosis: An FP’s primer on an enigmatic disease
Management includes ruling out alternate diagnoses, identifying occult/overt organ involvement, determining treatment, and recognizing worrisome features.
PRACTICE RECOMMENDATIONS
› Consider biopsy to aid in diagnosing sarcoidosis; it may be avoided with a high clinical suspicion for sarcoidosis (eg, Löfgren syndrome, lupus pernio, or Heerfordt syndrome). C
› Rule out alternative diagnoses such as infection, malignancy, collagen vascular disease, and vasculitis. C
› Identify extra-pulmonary organ involvement, as clinically indicated, by screening with a baseline eye examination; complete blood count; creatinine, alkaline phosphatase, and calcium levels; electrocardiogram, and other organ-specific studies. C
› Make a patient-centered decision whether to begin antiinflammatory treatment based on symptomatology and risk of organ failure or death. C
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
Pathology of early and advanced pulmonary sarcoidosis
Sarcoidosis is characterized by coalescing, tightly clustered, nonnecrotizing granulomas in the lung (FIGURE 4), most often located along the lymphatic routes of the pleura, interlobular septa, and bronchovascular bundles.41 Granulomas contain epithelioid cells or multinucleated giant cells surrounded by a chronic lymphocytic infiltrate. Typically, intracytoplasmic inclusions, such as Schaumann bodies, asteroid bodies, and blue bodies of calcium oxalates are noted within giant cells.
In chronic disease, lymphocytic infiltrate vanishes and granulomas tend to become increasingly fibrotic and enlarge to form hyalinized nodules rich with densely eosinophilic collagen. In 10% to 30% of cases, the lungs undergo progressive fibrosis.40 Nonresolving inflammation appears to be the major cause of fibrosis and the peribronchovascular localization leading to marked bronchial distortion.
Clinical features, monitoring, and outcomes
Pulmonary involvement occurs in most patients with sarcoidosis, and subclinical pulmonary disease is generally present, even when extrathoracic manifestations predominate.23 Dry cough, dyspnea, and chest discomfort are the most common symptoms. Chest auscultation is usually unremarkable. Wheezing is more common in those with fibrosis and is attributed to airway-centric fibrosis.42 There is often a substantial delay between the onset of symptoms and the diagnosis of pulmonary sarcoidosis, as symptoms are nonspecific and might be mistaken for more common pulmonary diseases, such as asthma or chronic bronchitis.43
Since sarcoidosis can affect pulmonary parenchyma, interstitium, large and small airways, pulmonary vasculature, and respiratory muscles, the pattern of lung function impairment on PFT varies from normal to obstruction, restriction, isolated diffusion defect, or a combination of these. The typical physiologic abnormality is a restrictive ventilatory defect with a decreased diffusing capacity of the lung for carbon monoxide (DLCO). Extent of disease seen on HRCT correlates with level of restriction.44 Airway obstruction can be multifactorial and due to airway distortion (more likely to occur in fibrotic lung disease) and luminal disease.45-48 The 6-minute walk test and DLCO can also aid in the diagnosis of SAPH and advanced parenchymal lung disease.
While monitoring is done clinically and with testing (PFT and imaging) as needed, the optimal approach is unclear. Nevertheless, longitudinal monitoring with testing may provide useful management and prognostic information.40 Pulmonary function can remain stable in fibrotic sarcoidosis over extended periods and actually can improve in some patients.49 Serial spirometry, particularly forced vital capacity, is the most reliable tool for monitoring; when a decline in measurement occurs, chest radiography can elucidate the mechanism.50,51
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