Representative Jennifer Wexton, Democrat of Virginia, announced on Monday that she would not seek re-election next year after receiving a diagnosis of a rare neurological disorder. Ms. Wexton, 55, who represents a competitive district in the Virginia suburbs west of Washington, D.C., revealed in a statement that she has progressive supranuclear palsy, which she described in a statement as “Parkinson’s on steroids.” “I’m heartbroken to have to give up something I have loved after so many years of serving my community,” she said. Ms. Wexton was elected to represent Virginia’s 10th Congressional District in 2018, defeating a two-term Republican incumbent, Barbara Comstock, by 12 percentage points. In April, Ms.…