Sarcoidosis is
a systemic disease of unknown causes characterized by granulomatous
inflammation of the lung in
about 90% of patients. The incidence is highest in North America
blacks ad northern European whites:among
blacks, women are most frequently affected than men. Onset of
disease is usually in the third
or fourth decade.
Patients
may present with malaise, fever, and dyspnea of insidious onset.
Alternatively, sarcoidosis may present
with symptoms referable to the skin, eyes, peripheral nerves,
liver or heart. Some patients are asymptomatic
and come to medical attention after abnormal findings (typically
bilateral hilar and paratracheal
lymphadenopathy) on routine chest radiographs. Physical findings
in the chest are typical of those
associated with interstitial lung involvement, if the parenchyma
is involved. Other findings may include
skin rashes, urethane nudism, parotid gland enlargement,, and
lymphadenopathy.
Laboratory
tests may show leukopenia, eosinophilia, an elevated erythrocyte
sedimentation rate, and hypercalcemia
(about 10% of patients) or hypercalciuria (20%). Angiotensin-converting
enzyme (ACE) levels are elevated
in 40-80% of patients with active sarcoidosis. This finding is
neither important nor specific
enough to have diagnostic significance. Ace is derived from the
cell membrane of epithelioid cells of
the sarcoid granuloma. Its synthesis is controlled by T lymphocytes.
Physiologic ges of decreased lung volumes
and diffusing capacity and more common signs. Skin test anergy
is present in 70%.
Radiographic
findings are variable and include bilateral hilar adenopathy
alone (stage 1). hilar adenopathy
and parenchymal involvement (stage II). or parenchymal involvement
alone (stage III). Parenchymal
involvement is usually manifested radiographically by diffuse
reticular infiltrates, but focal infiltrates,
acinar shadows, nodules, and rarely, cavitation may be seen.
Pleural effusion is noted in fewer than
10% of patients.
The
diagnosis of sarcoidosis generally requires histologic demonstration
of noncaseating granulomas in biopsies
from a patient with other typical associated manifestations.
Other granulomatous diseases (e.g. berylliosis,
tuberculosis) must be ruled out. If indicated, biopsy of easily
accessible sites (e.g. palpable lymph
nodes, skin lesions or salivary glands) is likely to provide
positive findings. Transbronchial lung biopsy
has a high yield of positive findings, especially in patients
with radiographic evidence of parenchymal
involvement. Most clinicians would agree that tissue biopsy is
not necessary when stage I radiographics
findings or detected in clinical situation that strongly favors
the diagnosis of sarcoidosis (e.g. a
young black female with erythema nodosum). Biopsy is essential
whenever clinical and radiographic findings
suggest the possibility of an alternative diagnosis such as lymphoma.
Bronchoalveolar lavage is useful
in following the activity of sarcoidosis in selected patients
but does not provide a specific diagnosis.
