The distinction between schizophrenia and chronic delusional syndromes (including the French concept of "psychose hallucinatoire chronique" [PHC] or chronic psychotic hallucinations, paraphrenia, and late paraphrenia) is currently used in various European countries, although there are no international criteria for chronic and bizarre delusions. The French concept of PHC is characterized by late-onset psychosis, predominantly in females, with rich and frequent hallucinations, but almost no dissociative features or negative symptoms. PHC and late-onset schizophrenia may have risk factors in common, which may help differentiate these disorders from young-onset schizophrenia, especially with regard to the potential role of (i) the estradiol hypothesis; (ii) the impact of sensory deficit; (Hi) putative specific brain abnormalities; or (iv) specific genetic mutations. In accordance with this hypothesis, and taking into account the familial aggregation analyses of PHC, here we evaluate the possibility that PHC represents a less severe form of schizophrenia, which would partly explain the "Sherman paradox" also observed in schizophrenia. The Sherman paradox describes the fact that multiplex families frequently have only one affected ascendant, meaning that an isolated sporadic case is at the origin of a highly loaded family. We thus propose that if unstable mutations are involved in the risk for schizophrenia, then PHC might represent a moderate disorder belonging to the schizophrenia spectrum phenotype.
Correction to: Preliminary comparative analysis of the genomes of selected field reisolates of the Mycoplasma synoviae vaccine strain MS-H reveals both stable and unstable mutations after passage in vivo
