Background and purpose:
The phenotype of IBMPFD [inclusion body myopathy with Paget's disease of the bone and frontotemporal dementia (FTD)] associated with valosin-containing protein (VCP) mutation is described in three families.
Probands were identified based on a pathological diagnosis of frontotemporal lobar degeneration with TDP-43-positive inclusions type IV. VCP sequencing was carried out. Clinical data on affected family members were reviewed.
Ohio family: four subjects presented muscle weakness and wasting. (One subject had both neuropathic and myopathic findings and another subject showed only evidence of myopathy. The etiology of weakness could not be ascertained in the remaining two subjects.) Two individuals also showed Parkinsonism (with associated FTD in one of the two). The proband's brain displayed FTLD-TDP type IV and Braak stage five Parkinson's disease (PD). A VCP R191Q mutation was found. Pennsylvania family: 11 subjects developed IBMPFD. Parkinsonism was noted in two mutation carriers, whilst another subject presented with primary progressive aphasia (PPA). A novel VCP T262A mutation was found. Indiana family: three subjects developed IBMPFD. FTD was diagnosed in two individuals and suspected in the third one who also displayed muscle weakness. A VCP R159C mutation was found.
We identified three families with IBMPFD associated with VCP mutations. Clinical and pathological PD was documented for the first time in members of two families. A novel T262A mutation was found. One individual had PPA: an uncommon presentation of IBMPFD.
"As mentioned above, the Austrian patient with polyneuropathy had diabetes. This was also the case in one patient with a R191Q mutation described by Spina et al.9 A review of 49 patients from 9 families revealed that 2 of the patients had diabetic neuropathy. "
[Show abstract][Hide abstract] ABSTRACT: Inclusion-body myopathy with Paget's disease of the bone and frontotemporal dementia (IBMPFD) is a rare, late-onset autosomal disorder arising from missense mutations in a gene coding for valosin-containing protein.
We report the case of a man carrying the previously described p.Arg159His mutation, who had an unusual axonal sensorimotor neuropathy as the first clinical manifestation of IBMPFD, and for whom diagnosis only became clear 8 years later when the patient developed frontotemporal dementia.
Peripheral neuropathy is a rare manifestation of IBMPFD. This underdiagnosed disorder should be considered when a patient develops dementia or has signs of Paget's disease.
[Show abstract][Hide abstract] ABSTRACT: Mutations in VCP cause multisystem degeneration impacting the nervous system, muscle, and/or bone. Patients may present with ALS, Parkinsonism, frontotemporal dementia, myopathy, Paget's disease, or a combination of these. The disease mechanism is unknown. We developed a Drosophila model of VCP mutation-dependent degeneration. The phenotype is reminiscent of PINK1 and parkin mutants, including a pronounced mitochondrial defect. Indeed, VCP interacts genetically with the PINK1/parkin pathway in vivo. Paradoxically, VCP complements PINK1 deficiency but not parkin deficiency. The basis of this paradox is resolved by mechanistic studies in vitro showing that VCP recruitment to damaged mitochondria requires Parkin-mediated ubiquitination of mitochondrial targets. VCP recruitment coincides temporally with mitochondrial fission, and VCP is required for proteasome-dependent degradation of Mitofusins in vitro and in vivo. Further, VCP and its adaptor Npl4/Ufd1 are required for clearance of damaged mitochondria via the PINK1/Parkin pathway, and this is impaired by pathogenic mutations in VCP.
[Show abstract][Hide abstract] ABSTRACT: Objective: To explore the putative connection between inclusion body myopathy, Paget disease, frontotemporal dementia (IBMPFD) and motor neuron disease (MND).
Methods: Clinical, genetic, and EMG characterization of 17 patients from 8 IBMPFD families.
Results: Limb weakness was the most common clinical manifestation (present in 15 patients, median onset age 38 years, range 25–52), with unequivocal evidence of upper motor neuron dysfunction in 3. EMG, abnormal in all 17, was purely neurogenic in 4, purely myopathic in 6, and mixed neurogenic/myopathic in 7. Cognitive/behavioral impairment was detected in at least 8. Mutations in VCP (R155H, R159G, R155C) were identified in 6 families, and in hnRNPA2B1 (D290V) in another family. The genetic cause in the eighth family has not yet been identified.
Conclusion: Mutations in at least 4 genes may cause IBMPFD, and its phenotypic spectrum extends beyond IBM, Paget disease, and frontotemporal dementia (FTD). Weakness, the most common and dis- abling manifestation, may be caused by muscle disease or MND. The acronym IBMPFD is, therefore, insufficient to describe disorders due to VCP mutations or other recently identified IBMPFD-associated genes. Instead, we favor the descriptor multisystem proteinopathy (MSP), which encompasses both the extended clinical phenotype and the previously described prominent pathologic feature of protein aggregation in affected tissues. The nomenclature MSP1, MSP2, and MSP3 may be used for VCP-, HNRNPA2B1-, and HNRNPA1-associated disease, respectively. Genetic defects in MSP implicate a range of biological mechanisms including RNA processing and protein homeostasis, both with potential relevance to the pathobiology of more common MNDs such as amyotrophic lateral sclerosis (ALS) and providing an additional link between ALS and FTD. Neurology" 2013;80:1–7
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