Inclusion body myopathy with Paget's disease of the bone and frontotemporal dementia (IBMPFD) is a rare late-onset autosomal dominant disorder due to a mutation of the valosin-containing protein (VCP) gene.
We report the case of a patient who developed progressive weakness of the limbs in his fifties, until he was confined to a wheelchair. At that time, he developed acute behavioural changes including irritability, severe anxiety and major depression, which led to him being hospitalised in a psychiatric hospital. He also suffered from aphasia and executive function impairment, which helped us to diagnose a behavioural form of frontotemporal dementia (FTD). The diagnosis of IBMPFD due to a mutation in the VCP gene was confirmed by a genetic study of the VCP gene (R155H mutation).
THE CLINICAL DIAGNOSIS OF IBMPFD IS SUGGESTED BY THE PRESENCE OF AT LEAST ONE OF THREE MAJOR MANIFESTATIONS AS FOLLOWS: inclusion body myopathy (mean onset at 42 years of age), Paget's disease of the bone and FTD (mean onset at 55 years of age). It is mostly the behavioural form of FTD (behavioural changes, executive dysfunction and aphasia). One interesting finding in our report is the predominance of the psychiatric symptoms at the beginning of the behavioural changes, which led to the diagnosis of FTD. The diagnosis of IBMPFD was confirmed by the genetic study: the R155H mutation found on exon 5 domain CDC48 is the most frequent of the 18 known mutations in the VCP gene.