Results for “Multisystem Proteinopathy”

PubMed2007

Multisystem Proteinopathy

CLINICAL CHARACTERISTICS: Multisystem proteinopathy (MSP) is a genetically heterogeneous, multisystem degenerative disorder characterized by adult-onset proximal and distal muscle weakness (clinically resembling a limb-girdle muscular dystrophy syndrome), early-onset Paget disease of bone (PDB), and premature frontotemporal dementia (FTD). Muscle weakness progresses to involve other limb and respiratory muscles. PDB involves focal areas of increased bone turnover that typically lead to spine and/or hip pain and localized enlargement and deformity of the long bones; pathologic fractures occur on occasion. Early stages of FTD are characterized by dysnomia, dyscalculia, comprehension deficits, and paraphasic errors, with minimal impairment of episodic memory; later stages are characterized by inability to speak, auditory comprehension deficits for even one-step commands, alexia, and agraphia. Mean age at diagnosis for muscle disease is 43 years, PDB is 41 years, and FTD is 56 years. Dilated cardiomyopathy, amyotrophic lateral sclerosis, and Parkinson disease are now known to be part of the spectrum of findings associated with MSP. DIAGNOSIS/TESTING: The diagnosis of MSP is established in a proband with typical clinical findings and a heterozygous pathogenic variant in VCP, HNRNPA1, HNRNPA2B1, or SQSTM1 identified by molecular genetic testing. MANAGEMENT: Treatment of manifestations: Weight control to avoid obesity; physical therapy and stretching exercises to promote mobility and prevent contractures; occupational therapy and mechanical aids (canes, walkers, orthotics, wheelchairs) as needed for ambulation/mobility; surgical intervention for foot deformity and scoliosis as needed; respiratory aids when indicated; assisted living arrangements for muscle weakness and/or dementia; bisphosphonates to relieve pain and disability from PDB; social and emotional support; education regarding safety precautions. Surveillance: Echocardiogram and electrocardiogram with repeat cardiac evaluation every two to three years or earlier if symptomatic; annual pulmonary function studies; sleep studies as clinically indicated; annual alkaline phosphatase measurement; skeletal imaging as indicated for evaluation of PDB; neurologic and neuropsychological assessment every two to three years or more frequently as needed; multidisciplinary monitoring for respiratory, cardiac, musculoskeletal, and cognitive decline. GENETIC COUNSELING: MSP is inherited in an autosomal dominant manner. Most individuals diagnosed with MSP have an affected parent. Estimates based largely on VCP-MSP suggest that approximately 5% of individuals have a de novo pathogenic variant. Each child of an individual with MSP has a 50% chance of inheriting the MSP-related pathogenic variant. Marked intrafamilial variability may be observed among heterozygous family members, including differences in age at onset, severity, rate of progression, and the specific combination of manifestations. Once the MSP-related pathogenic variant has been identified in an affected family member, predictive testing for at-risk family members and prenatal/preimplantation genetic testing are possible.

Inclusion Body Myopathy with Early-Onset Paget Dis↗

PubMed2026

The long road to diagnosis: recessive PMPCB deficiency hidden behind a dominant familial VCP defect.

Multiple mitochondrial dysfunctions syndrome 6 (MMDS6), caused by biallelic likely pathogenic variants in PMPCB, is an extremely rare autosomal recessive childhood-onset neurodegenerative disorder, with only six reported cases to date, most resulting in early mortality. Pathogenic variants in VCP cause multisystem proteinopathy 1 (MSP1), an autosomal dominant adult-onset disorder encompassing inclusion body myopathy (IBM), frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS), typically presenting in mid-adulthood. We describe a 23-year-old female with two likely pathogenic variants presumed to be in trans in PMPCB and a co-occurring pathogenic VCP variant. She was misdiagnosed for over 20 years with early-onset VCP-related neurodegeneration due to a maternal family history of ALS. Her disease began at birth with microcephaly and progressed throughout childhood, including developmental regression, cerebellar and cerebral atrophy, optic atrophy, seizures, spasticity, dysarthria, and loss of ambulation. Initial genetic testing identified only the familial VCP variant. Updated genomic sequencing at age 23 revealed two likely pathogenic PMPCB variants, strong supporting a diagnosis of MMDS6. Her clinical features closely align with previously reported MMDS6 cases and are inconsistent with the typical adult-onset phenotype of VCP-associated disorders. While she shares overlapping features with VCP-related disease (limb-girdle weakness, spasticity, FTD), the timing and severity of her neurodevelopmental findings support MMDS6 as the primary diagnosis. Early mitochondrial dysfunction may predispose her to an accelerated or more severe future VCP-associated phenotype. This is the first report of combined likely pathogenic and pathogenic variants in PMPCB and VCP respectively, expanding the phenotypic spectrum of both disorders. The case underscores the necessity of periodic re-evaluation with advanced genetic testing, highlights important ethical and familial implications, and informs future diagnosis and management of patients with overlapping rare genetic conditions.

Dual molecular diagnosis↗