UBQLN2 and early-onset autosomal dominant Alzheimer disease: Advances in molecular medicine have begun to reveal specific proteins that accumulate in specific syndromes—for instance, α-synuclein in Parkinson’s disease (PD); Aβ and tau in Alzheimer’s disease (AD); polyglutamine proteins in various CAG trinucleotide repeat disorders; superoxide dismutase 1 (SOD1), TAR DNA-binding protein 43 (TDP43), FUS, optineurin (OPTN), ubiquilin 2 (UBQLN2), and dipeptide repeat protein (DRP) in amyotrophic lateral sclerosis (ALS) [4–7].