"Original Patent" vs. Written Description — A New Reissue Gauntlet?

In two opinions issued in the past few weeks, the Federal Circuit has shaken up two requirements of the reissue statute that most practitioners don't think about much. 35 USC 251(a) authorizes reissue of a patent "for the invention disclosed in the original patent." 35 USC 251(c) provides that "[t]he provisions of this title relating to applications for patent shall be applicable to applications for reissue of a patent," which includes the written description requirement of 35 USC 112(a). The "conventional" wisdom up to now has held that these requirements are more or less synonymous (and not considered arduous). Now, we aren't so sure.

In Forum US, Inc. v. Flow Valve, LLC, ___ F.3d ____ 2019 U.S. App. LEXIS 18055 (Fed. Cir., June 17, 2019), the district court invalidated a reissue patent on summary judgment on the ground that the reissue claims did not comply with the "original patent" requirement of the reissue statute. The Federal Circuit affirmed, agreeing on