Abstract
Background: Inclusion body myopathy associated with Paget disease of bone (PDB) and/or frontotemporal dementia (IBMPFD) is a rare, autosomal dominant condition, characterized by adult-onset muscle weakness, early-onset PDB, and premature frontotemporal dementia. Paget’s disease is a chronic disorder of bone resulting in increased bone resorption, followed by a disorganized and excessive formation of bone.
Clinical Case: A 43 year old gentleman was referred to neurology services with foot drop, limb weakness and cognitive impairment. Following a prolonged period of diagnostic evaluation a mutation in valosin-containing protein (VCP) gene was uncovered IBMPFD has a variable phenotype which may include PDB. This gentleman denied bony pain and had an alkaline phosphatase within reference range. Plain film radiographs at multiple sights demonstrated no signs of PDB. An MRI whole body was performed which reported coarse trabecular markings in L2 vertebral body and multilevel degenerative changes with bridging osteophytes in the lumbar spine consistent with PDB.
At initial review in endocrine clinic, he denied fractures or bone pain. He had no signs of increased cardiac output or cranial nerve deficits. A radionuclide bone scan identified intense radiopharmaceutical accumulation in L2 vertebral body consistent with MRI findings and also curvilinear increased activity in the left occipital bone and low-grade activity in the left hip, thus confirming polyostotic Paget’s disease.
He received a 5mg IV infusion of zolendronate, side effects of which included myalgia, pyrexia and lethargy.
Six months following the zoledronate infusion a repeat bone scan demonstrated that the extent of uptake at affected sites had decreased significantly.
He subsequently fractured his left femur following a mechanical fall. PDB can affect up to 50% of patients with IBMFTD. PDB can lead to complications such as bone pain, localized pain and deformity of the long bones, pathologic fractures and deafness. This case highlights the association of Paget’s disease with IBMFTD and as it can be asymptomatic, as in our case, radiological imaging is required for diagnosis. It also reminds us that Paget’s disease can be due to genetic causes. Understanding the role of VCP in the cell cycle may help in further understanding bone physiology.
Mickey Mouse Sign on Bone Scan in the Monostotic Form of Paget’s Disease Mimicking Osseous Metastasis
