Context: Sjogren's syndrome (SS) and sarcoidosis are diseases of unkno
wn origin that are considered to result from abnormal regulation of th
e immune system. Pulmonary involvement by SS and sarcoidosis may have
similar clinical and radiographic manifestations, making it difficult
for the clinician to distinguish between these diseases. Objectives: T
his study was undertaken to analyze the characteristics of SS and sarc
oidosis in the lung to identify distinguishing features that may assis
t clinicians in the differentiation of these conditions. Design: We pr
esent two cases with severe pulmonary impairment in which the distinct
ion between SS and sarcoidosis required lung tissue biopsy. The litera
ture regarding the pulmonary manifestations of these diseases is revie
wed. Results: The clinical, pathological, radiographic, and physiologi
cal characteristics of lung disease in the setting of SS and sarcoidos
is can be very similar, preventing a diagnosis solely on clinical grou
nds. This is exemplified in the two cases reported. In one patient who
carried the diagnosis of sarcoidosis, examination of lung tissue reve
aled lymphocytic interstitial pneumonitis consistent with SS. In the o
ther patient, who had previously been diagnosed with SS on clinical gr
ounds, examination of lung tissue showed lymphocytic interstitial pneu
monitis with scattered noncaseating granulomas, suggesting the possibi
lity of coexisting SS and sarcoidosis. A literature review indicated t
hat lung involvement by SS may be difficult to distinguish from that o
f sarcoidosis. Furthermore, several cases have been reported in which
both diseases coexisted. Conclusions: Because SS and sarcoidosis may c
oexist and present with similar pulmonary manifestations, aggressive e
valuation including tissue biopsy may be required. However, even tissu
e biopsy may not distinguish between these entities unless noncaseatin
g granulomas are seen (in the case of sarcoidosis) or isolated lymphoc
ytic interstitial pneumonitis is detected (in the case of SS). When bo
th features (ie; noncaseating granuloma and lymphocytic interstitial p
neumonitis) are encountered in the same organ, we believe these diseas
es are coexisting. Distinguishing both conditions may have prognostic
implications, because sarcoidosis may present as an autolimiting proce
ss and frequently resolves spontaneously without significant residual
functional impairment. In contrast, pulmonary involvement with SS ofte
n leads to permanent defects and may progress to incapacitating diseas
e. Semin Arthritis Rheum 28:31-40. Copyright (C) 1998 by W.B. Saunders
Company.