Pitfalls in diagnostic myopathology of sporadic inclusion body myositis (SIBM).

Sporadic inclusion body myositis (SIBM) is the most common idiopathic inflammatory myopathy in Caucasians over the age of 50 years. The prevalence of SIBM in the Asian population was initially thought to be very low, although the recent study showed that the prevalence of SIBM in Japan is in fact similar to the prevalence in Australia and the USA. SIBM is a refractory myositis with associated myodegenerative features mimicking the neuropathology of Alzheimer’s disease. The diagnosis of definite SIBM requires the typical clinical features and the presence of an autoaggressive inflammatory reaction, rimmed vacuoles, and congophilic deposits or tubulofilamentous inclusions. About one-fourth of patients with the typical clinical features of SIBM did not fulfill the pathological criteria of the definite SIBM. These canonical biopsy features may be absent in the early stage of the disease. Here we review the typical findings and the diagnostic pitfalls of the muscle biopsy in SIBM.

Myofibrillar myopathy with limb-girdle phenotype in a Thai patient.

Myofibrillar myopathy (MFM) encompasses a genetically and clinically heterogeneous group of inherited or sporadic skeletal muscle disorders characterized pathologically by the presence of myofibrillar dissolution associated with accumulation of myofibrillar degradation products and ectopic expression of multiple proteins especially Z-disk related proteins. Patients with MFM initially present with muscle weakness and commonly developed cardiomypathy in the advanced stage. To date, mutations of genes encoding Z-disk proteins or proteins maintaining myofibrillar integrity including ZASP, MYOT, DES, FLNC and CRYAB underlie MFM. The authors herein report a 29-year-old Thai woman with a clinical diagnosis of autosomal dominant limb-girdle muscular dystrophy (LGMD1) who has one affected grandmother. The patient was subsequently found to have MFM based on her myopathological findings. Analyses of all MFM-genes known to date revealed no mutations. The current case emphasizes the importance of muscle biopsy in LGMD1 patients and a wide range of phenotypic variations among patients with MFM. The causative genes underlying the majority of MFM remain uncovered. Close monitoring of the cardiac function is crucial to prevent mortality among these patients.

Floppy infant caused by MTM1 mutation: a first genetically-confirmed X-linked myotubular myopathy patient in Thailand.

Floppy infant syndrome (FIS) refers to a condition wherein an infant manifests generalized hypotonia since birth or in early life. It is heterogeneous and can be caused by various central nervous system disorders, neuromuscular diseases and genetic disorders. X-linked myotubular myopathy (XMTM) is a progressive congenital myopathy morphologically characterized by the presence of centrally placed nuclei in numerous muscle fibers without any other particular pathological abnormalities. Patients are frequently born with floppiness and respiratory distress. The vast majority of patients carry a truncating or missense mutation in MTM1. The authors report here a full term male baby with clinicopathological features of XMTM. The diagnosis is validated by the finding of a c. 141-144delAGAA mutation ofMTM1. To the best of the authors' knowledge, the present case is the first genetically confirmed XMTM in Thailand. A brief review of various neuromuscular disorders causing floppy infant syndrome is also included.

Primary peripheral primitive neuroectodermal tumor of the ovary with an epithelial cyst : A case report and review of literature.

Peripheral primitive neuroectodermal tumor (pPNET) has some histologic resemblance to a classic central primitive neuroectodermal tumor (cPNET), however it is distinctively different from cPNET by its CD99 immunoreactivity, characteristic chromosomal translocation, t(11;22)(q24:q12) and EWS/FLI-1 chimeric mRNA. Peripheral PNETs have a predilection for soft tissues rather than for viscera. Only 15 cases of primary ovarian PNET have been reported, and only one case was proven to be pPNET. Ovarian PNET is an aggressive tumor. We report a case of a 40-year-old Thai woman with a Stage IIIb right ovarian PNET is an aggressive tumor. Despite debulking operation and vigorous adjuvant chemotherapy, the patient died of disease 6 months later. Grossly, the tumor was solid and cystic. Microscopically, the former displayed unique features mimicking cPNET, but the pPNET phenotype was validated by CD99 staining. The solid portion also contained mucin-producing gland-like structures, previously described as ependymal diffentiation. In the cystic portion, the histology demonstrated epithelial linning tissue resembling cystadenoma of borderline malignancy of the ovary. It is generally accepted that both cPNET and pPNETs can have polyphenotypic differentiation. PNETs can be originated from either totipotential germ cells, neural crest remnant or mullerian-derived cells.

Myopathology, a 14-year Siriraj experience: What have we learned.

Neuromuscular laboratory, Department of Pathology Siriraj Hospital was established in 1989. Within fourteen years, 315 specimens from 304 patients were received. The patients’ age ranged from 22-week gestation to 76 years old. The ratio of males to female was 1.11:1. Muscular dystrophies comprised 26.63%, non-specific changes 25.66%, primary myopathies, including unclassified myopathy 13.82%, neurogenic muscle diseases 12.82% dysimmune and infectious myopathies 8.89%, mitochondrial myopathy 4.94% and others 7.24%. Summaries of our patients were described.