Summary An elderly patient with no abnormal bleeding presented with prolongation of the activated partial thromboplastin time (aPTT). Preincubation of plasma with aPTT reagent caused shortening of the abnormal clotting time. Plasma prekallikrein (PK) activity and antigen were <5 u/dL. Molecular analysis showed a homozygous Arg94Stop substitution in the PK gene, predicted to prevent expression of the mutant allele. The five heterozygous offspring of the proband each showed a normal aPTT but reduced PK activity and antigen. This is the first description of a kindred in which absence of expression of one or both PK alleles has been confirmed by genotype.

A potential link between switching to aripiprazole and worsening of psychosis was first reported in the early 2000s. There have since been numerous published case reports describing this phenomenon, but only recently has the concept of a theoretical aripiprazole-induced dopamine supersensitivity psychosis (DSP) caused by D2 receptor activation in patients undergoing a switch to aripiprazole appeared in the literature. There is less awareness in clinical practice of the possibility of inducing DSP with aripiprazole, which may be particularly severe in some patients. The objective of this article is to present four cases demonstrating rapid and dramatic onset of DSP during switching to aripiprazole. In each case, a patient with a Diagnostic and statistical manual of mental disorders (5th ed.) diagnosis of schizophrenia experienced severe worsening of psychosis within 4–5 days of abrupt switching to aripiprazole from a full D2 antagonist. To our knowledge, this is the first case series characterizing the previously well-documented worsening of psychosis during switching to aripiprazole specifically as aripiprazole-induced DSP. We discuss clinical relevance, prevention and future directions. Careful cross-titration per clinical practice guidelines may reduce occurrence of DSP during aripiprazole switching or augmentation treatment.