Necrotizing sarcoid granulomatosis - Is it different from nodular sarcoidosis?

Background: Necrotizing sarcoid granulomatosis (NSG) was initially defined as a granulomatosis with features in between sarcoidosis and Wegener's granulomatosis (WG), but without extrapulmonary involvement. Subsequent reports have shown that extrapulmonary involvement does exist, and some have suggested NSG as a variant of sarcoidosis. Material and Methods: We studied 10 cases from 3 institutions, and compared clinical and histologic features with those of nodular sarcoidosis and WG. We have analyzed the 10 cases for mycobacterial chaperonin and for the insertion sequence 6110 by PCR. Results and Conclusions: Nodular aggregates of granulomas in NSG were similar to those seen in nodular sarcoidosis. Granulocytic vasculitis, a hall-mark of WG was not seen in any of the NSG cases. Granulomatous vasculitis was a common feature in cases of NSG, and did not differ from that seen in sarcoidosis. The only unique feature of NSG is infarct-like necrosis, induced by the vasculitis, which might also be interpreted as a function of the duration of the vasculitis, leading ultimately to vascular obstruction. NSG based on our morphologic findings is best classified as a variant of nodular sarcoidosis. In contrast to our findings in sarcoidosis mycobacterial DNA was not found in any of the 10 cases.