Sarcoidosis: An FP’s primer on an enigmatic disease

High-resolution computed tomography (HRCT). Micronodules in a perilymphatic distribution with upper lobe predominance combined with subcarinal and symmetrical hilar lymph node enlargement is practically diagnostic of sarcoidosis in the right clinical context. TABLE 3^21,23,25,32 and FIGURE 2^21,23,25,32 summarize the common CT chest findings of sarcoidosis.

Advanced imaging such as (18)F-fluorodeoxyglucose positron emission tomography (PET) and magnetic resonance imaging (MRI) are used in specialized settings for advanced pulmonary, cardiac, or neurosarcoidosis.

Tissue biopsy

Skin lesions (other than erythema nodosum), eye lesions, and peripheral lymph nodes are considered the safest extrapulmonary locations for biopsy.^21,25 If pulmonary infiltrates or lymphadenopathy are present, or if extrapulmonary biopsy sites are not available, then flexible bronchoscopy with biopsy is the mainstay for tissue sampling.²⁵

Bronchoalveolar lavage (BAL), transbronchial biopsy (TBB), endobronchial biopsy (EBB), and endobronchial ultrasound (EBUS) are invaluable modalities that have reduced the need for open lung biopsy. BAL in sarcoidosis can show lymphocytosis > 15% (nonspecific) and a CD4:CD8 lymphocyte ratio > 3.5 (specificity > 90%).^21,22 TBB is more sensitive than EBB; however, sensitivity overall is heightened when both of them are combined. The advent of EBUS has increased the safety and efficiency of needle aspiration of mediastinal lymph nodes. Diagnostic yield of EBUS (~80%) is superior to that with TBB and EBB (~50%), especially in stage I and II sarcoidosis.³⁷ The combination of EBUS with TBB improves the diagnostic yield to ~90%.³⁷

The decision to obtain biopsy samples hinges on the nature of clinical and radiologic findings (FIGURE 3).^22,25,26

Continue to: Laboratory studies