Background/Purpose:

Lung involvement is common in both sarcoidosis (up to 90%) and autoimmune rheumatic diseases (ARDs). Case reports have suggested distinct clinical manifestations when sarcoidosis is diagnosed with other ARDs. However clinical and serological manifestations have not been described in larger cohorts.

Methods:

A retrospective medical chart review of patients attending our centre with a diagnosis of sarcoidosis and ARD. ARD was classified as systemic sclerosis (SSc), lupus, myositis or inflammatory arthritis (IA). Organ manifestations were further classified into sarcoid or ARD as the main pathology.

Comparison was made between the SSc/sarcoid cohort and other ARD/sarcoid cohort. Statistical analysis of organ involvement was performed using Fisher exact test.

Results:

61 patients (17 males) with overlap sarcoid and ARD were identified, with 5 patients having more than one ARD diagnosis. The mean time lag between sarcoid diagnosis to ARD diagnosis was 51 months (median 71 mths) (range -432 to 372 mths). Sarcoid predates diagnosis of ARD in 68.8% cases.  

The majority of patients had an overlap diagnosis of SSc (n=22, 36.1%), of those 77.3% were limited SSc. In the SSc/sarcoid cohort, 92% patients were ANA positive, 35% Scl70 positive, and 21% ACA positive.

In the ARD/sarcoid cohort, the most frequent overlap diagnosis was IA (72%). 23% were ANA positive, 35.8% rheumatoid factor positive, and 30.8% anti-CCP positive.

The frequency of major organ involvement was statistically different for lung disease, arthritis and sarcoid-skin involvement between SSc/sarcoid and ARD/sarcoid cohorts. A trend of increased frequency of pulmonary hypertension in SSc/sarcoid cohort was observed (table 1).

Further evaluation of interstitial lung disease (ILD) highlighted, overall 32% was attributable to sarcoid, and 19% related to ARD. In the SSc/sarcoid cohort, 22% had features of sarcoid ILD (bronchovascular beading or pulmonary nodularity), 45.5% had ILD consistent with SSc (non-specific interstitial pneumonia (NSIP)). In contrast, 38% of the ARD/sarcoid cohort had sarcoid predominant ILD (peribronchovascular beading, pulmonary nodules, and cystic lung disease), and 5% had ARD ILD (NSIP-ILD, and organising pneumonia). Baseline FVC was not different between SSc/sarcoid and ARD/sarcoid ILD cohorts (91.6% and 86.2% respectively).

Conclusion:

We report the largest cohort to date of patients with a concomitant diagnosis of sarcoidosis and ARD from a single centre cohort. Our data suggest that lung involvement in overlap SSc/sarcoid is less frequent than expected for each disease in isolation. The significant difference between arthritis between the SSc/sarcoid group and ARD/sarcoid group is likely due to the high proportion of IA in the latter group.

Our results highlight the importance of recognising concurrent sarcoidosis in multisystem ARD, especially as this may affect treatment and outcome.