Definition and Epidemiology

Sarcoidosis is a multisystem, inflammatory, granulomatous disease of unknown origin that commonly affects young and middle-aged adults. It involves the lungs and intrathoracic lymph nodes in more than 90% of affected patients, but it may essentially affect any organ (Table 115-1). More than 80% of patients are 20 to 45 years of age; the disease is rare in children and older adults. The incidence may vary with geographic location. In Europe, the United Kingdom, Japan, and North America, incidence rates of 5 to 40 per 100,000 population have been cited. The incidence of sarcoidosis in the United States is higher in African Americans than in whites, with greater morbidity reported. Reports of sarcoidosis appear to be rare in Africa, India, and Central and South America, probably because of the absence of mass screening programs and the presence of more common granulomatous diseases such as tuberculosis.¹ No clear genetic basis has been established for sarcoidosis, but genetic factors may modulate its evolution and expression. Sarcoidosis is commonly seen in families; the likelihood for development of the disease ranges from 26% to 73% in individuals with an affected first-degree relative.²

The characteristic pathologic feature of sarcoidosis is the noncaseating granuloma. The collection of macrophages and T cells that compose the granuloma releases various chemokines and cytokines, including tumor necrosis factor-α.²

The granuloma is likely to be preceded by an alveolitis that involves the interstitium more than the alveolar spaces. Although the initial antigen is unknown, the alveolitis begins an accumulation of helper T lymphocyte (CD4) cells and macrophages. It is believed that activated macrophages may be responsible for the eventual development of fibrosis in some patients with sarcoidosis.

In the lung, granulomatous inflammation and fibrosis result in ventilation/perfusion imbalance and widening of the alveolar-arterial oxygen gradient. In the early stages, PaO₂ may be within the normal range at rest but decreases with exertion.

Clinical Presentation and Physical Examination

Sarcoidosis may affect almost any organ system; however, 90% of affected individuals have pulmonary involvement.³ Sarcoidosis can occur in acute, subacute, or chronic form and is initially discovered asymptomatically with an abnormal chest radiograph in approximately 50% of patients.² Patients who are symptomatic with this disorder often have nonspecific pulmonary symptoms—dry cough, dyspnea, chest pain, fever, fatigue, anorexia, weight loss, and, occasionally, chills and night sweats. The nonspecificity of these symptoms can delay diagnosis.¹ The symptoms and related organ involvement consistent with sarcoidosis are listed in Table 115-1. Involvement of the upper airways and posterior pharynx may result in upper airway obstruction with worsening symptoms of dyspnea. Hoarseness and nasal obstruction may occur as a result of vocal cord and nasal mucosa granulomas (polyps). Hemoptysis is rarely seen; when present, it suggests mycetoma.⁴

It is unusual for adventitious lung sounds to be detected on auscultation. Wheezing is occasionally audible in patients with advanced disease. Digital clubbing is rare. Dyspnea, dry cough, and chest pain occur commonly. Chest pain can be severe and difficult to distinguish from cardiac chest pain.³

Rheumatologic symptoms occur in 4% to 38% of patients with sarcoidosis.⁵ These can manifest as an acute arthritis commonly involving the ankle, chronic polyarthritis, or myopathy.

Ocular lesions are seen in 20% of patients; anterior uveitis is seen most commonly. Symptoms may include redness, photophobia, and decreased visual acuity.¹ Other ocular lesions seen include posterior uveitis, retinal vasculitis, keratoconjunctivitis, and conjunctival follicles.²

Skin lesions are seen in 20% to 30% of patients. A maculopapular rash over the face and hairline is the most common subacute lesion.³ Erythema nodosum is seen more commonly in women; when it occurs in combination with hilar adenopathy, polyarthralgias, and fever, it is referred to as Löfgren syndrome.³

Clinical involvement of the central nervous system is unusual, but cranial nerve involvement can be seen. Asymptomatic granulomas can occur in any part of the female reproductive system, including the breast.

Diagnostics

Chest radiographs are abnormal in more than 90% of patients. In general, one of the following patterns is demonstrated: (1) bilateral hilar lymphadenopathy (BHL; 50% to 80% of cases); (2) parenchymal interstitial infiltrates (25% to 50%), with a predilection for upper and mid lung field distribution; or (3) both lymphadenopathy and interstitial disease. BHL is often the lesion that suggests the diagnosis of sarcoidosis.

Unless lymphadenopathy is present, the appearance of the chest radiograph may be indistinguishable from that of other interstitial lung disorders. Typically, radiographic lesions are bilateral and are distributed relatively symmetrically; asymmetric involvement is occasionally seen.

Staging systems based on the appearance of the chest radiograph have been in widespread use since 1957. The consensus now favors the following classification²:

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