V. Fabian

Progressive myopathy with up-regulation of MHC-I associated with statin therapy

Statins can cause a necrotizing myopathy and hyperCKaemia which is reversible on cessation of the drug. What is less well known is a phenomenon whereby statins may induce a myopathy, which persists or may progress after stopping the drug. We investigated the muscle pathology in 8 such cases. All had myofibre necrosis but only 3 had an inflammatory infiltrate. In all cases there was diffuse or multifocal up-regulation of MHC-I expression even in non-necrotic fibres. Progressive improvement occurred in 7 cases after commencement of prednisolone and methotrexate, and in one case spontaneously. These observations suggest that statins may initiate an immune-mediated myopathy that persists after withdrawal of the drug and responds to immunosuppressive therapy. The mechanism of this myopathy is uncertain but may involve the induction by statins of an endoplasmic reticulum stress response with associated up-regulation of MHC-I expression and antigen presentation by muscle fibres.

Mutations in KLHL40 Are a Frequent Cause of Severe Autosomal-Recessive Nemaline Myopathy

Nemaline myopathy (NEM) is a common congenital myopathy. At the very severe end of the NEM clinical spectrum are genetically unresolved cases of autosomal-recessive fetal akinesia sequence. We studied a multinational cohort of 143 severe-NEM-affected families lacking genetic diagnosis. We performed whole-exome sequencing of six families and targeted gene sequencing of additional families. We identified 19 mutations in KLHL40 (kelch-like family member 40) in 28 apparently unrelated NEM kindreds of various ethnicities. Accounting for up to 28% of the tested individuals in the Japanese cohort, KLHL40 mutations were found to be the most common cause of this severe form of NEM. Clinical features of affected individuals were severe and distinctive and included fetal akinesia or hypokinesia and contractures, fractures, respiratory failure, and swallowing difficulties at birth. Molecular modeling suggested that the missense substitutions would destabilize the protein. Protein studies showed that KLHL40 is a striated-muscle-specific protein that is absent in KLHL40-associated NEM skeletal muscle. In zebrafish, klhl40a and klhl40b expression is largely confined to the myotome and skeletal muscle, and knockdown of these isoforms results in disruption of muscle structure and loss of movement. We identified KLHL40 mutations as a frequent cause of severe autosomal-recessive NEM and showed that it plays a key role in muscle development and function. Screening of KLHL40 should be a priority in individuals who are affected by autosomal-recessive NEM and who present with prenatal symptoms and/or contractures and in all Japanese individuals with severe NEM.

Laing early onset distal myopathy: slow myosin defect with variable abnormalities on muscle biopsy

Background: Laing early onset distal myopathy (MPD1) is an autosomal dominant myopathy caused by mutations within the slow skeletal muscle fibre myosin heavy chain gene, MYH7. It is allelic with myosin storage myopathy, with the commonest form of familial hypertrophic cardiomyopathy, and with one form of dilated cardiomyopathy. However, the clinical picture of MPD1 is distinct from these three conditions. Objective: To collate and discuss the histological features reported in the muscle biopsies of MPD1 patients and to outline the clinical features. Results: The phenotype of MPD1 was consistent, with initial weakness of great toe/ankle dorsiflexion, and later development of weakness of finger extension and neck flexion. Age of onset was the only variable, being from birth up to the 20s, but progression was always very slow. The pathological features were variable. In this retrospective series, there were no pathognomonic diagnostic features, although atrophic type I fibres were found in half the families. Rimmed vacuoles are consistently seen in all other distal myopathies with the exception of Myoshi distal myopathy. However, they were found in a minority of patients with MPD1, and were not prominent when present. Immunohistochemical staining for slow and fast myosin showed co-expression of slow and fast myosin in some type I fibres, possibly indicating a switch to type II status. This may be a useful aid to diagnosis. Conclusions: The pathological findings in MPD1 are variable and appear to be affected by factors such as the specific muscle biopsied, the age of the patient at biopsy, and the duration of disease manifestations.

Rescue of skeletal muscle alpha-actin-null mice by cardiac (fetal) alpha-actin.

Skeletal muscle α-actin (ACTA1) is the major actin in postnatal skeletal muscle. Mutations of ACTA1 cause mostly fatal congenital myopathies. Cardiac α-actin (ACTC) is the major striated actin in adult heart and fetal skeletal muscle. It is unknown why ACTC and ACTA1 expression switch during development. We investigated whether ACTC can replace ACTA1 in postnatal skeletal muscle. Two ACTC transgenic mouse lines were crossed with Acta1 knockout mice (which all die by 9 d after birth). Offspring resulting from the cross with the high expressing line survive to old age, and their skeletal muscles show no gross pathological features. The mice are not impaired on grip strength, rotarod, or locomotor activity. These findings indicate that ACTC is sufficiently similar to ACTA1 to produce adequate function in postnatal skeletal muscle. This raises the prospect that ACTC reactivation might provide a therapy for ACTA1 diseases. In addition, the mouse model will allow analysis of the precise functional differences between ACTA1 and ACTC.

Consensus neuropathological diagnosis of common dementia syndromes: testing and standardising the use of multiple diagnostic criteria

Abstract. The aim of this study was to assess the variation between neuropathologists in the diagnosis of common dementia syndromes when multiple published protocols are applied. Fourteen out of 18 Australian neuropathologists participated in diagnosing 20 cases (16 cases of dementia, 4 age-matched controls) using consensus diagnostic methods. Diagnostic criteria, clinical synopses and slides from multiple brain regions were sent to participants who were asked for case diagnoses. Diagnostic sensitivity, specificity, predictive value, accuracy and variability were determined using percentage agreement and kappa statistics. Using CERAD criteria, there was a high inter-rater agreement for cases with probable and definite Alzheimers disease but low agreement for cases with possible Alzheimers disease. Braak staging and the application of criteria for dementia with Lewy bodies also resulted in high inter-rater agreement. There was poor agreement for the diagnosis of frontotemporal dementia and for identifying small vessel disease. Participants rarely diagnosed more than one disease in any case. To improve efficiency when applying multiple diagnostic criteria, several simplifications were proposed and tested on 5 of the original 20 cases. Inter-rater reliability for the diagnosis of Alzheimers disease and dementia with Lewy bodies significantly improved. Further development of simple and accurate methods to identify small vessel lesions and diagnose frontotemporal dementia is warranted.

Collecting duct carcinoma of the kidney: a report of three cases and review of the literature

Summary Collecting duct carcinoma (CDC) of the kidney is a rare neoplasm arising from the medullary collecting ducts. The clinicopathological features of three cases are here presented to add to the 42 cases reported so far in the English language literature. Hematuria is the most common presenting symptom, although 10% of patients present with metastatic disease, often in neck lymph nodes. The tumor mass is typically centred on the medulla of the kidney and extends into the cortex. Radiological diagnosis may be difficult because the radiological features of CDC are poorly described. The histological appearances have been described as tubulo‐papillary, tubular, solid and sarcomatoid. Intracytoplasmic mucin may be present. The typical immunohistochemical profile is positive staining with antibodies for low and high molecular weight keratin and epithelial membrane antigen (EMA) and positive staining with the lectin Ulex europaeus agglutinin. Literature reports of cytogenetic characterisation show loss of chromosomes resulting in monosomies. Prognosis is poor as more than half of the reported cases have developed metastases or died within two years of presentation.Abbreviations: CDC, collecting duct carcinoma; EMA, epithelial membrane antigen; FNA, fine needle aspiration; RCC, renal cell carcinoma.

The association of sporadic inclusion body myositis and Sjögren's syndrome in carriers of HLA-DR3 and the 8.1 MHC ancestral haplotype

Sporadic inclusion body myositis (sIBM) usually occurs as an isolated condition, but it may occur in association with another autoimmune disorder such as Sjögrens syndrome. We reviewed sIBM cases with Sjögrens syndrome (sIBM/SS) from the Perth Inflammatory Myopathies Database to determine whether they are distinguishable from other sIBM cases. Six such cases were identified, representing 12% of all sIBM cases. Muscle biopsies confirmed the presence of an inflammatory myopathy with rimmed vacuoles and the characteristic muscle fibre inclusions of sIBM. Five of the six were females, contrasting with a 2:1 male preponderance in the rest of the sIBM cohort. The mean age-at-onset and the pattern of muscle weakness were similar in the two groups. Four out of five sIBM/SS patients treated with immune therapies had improvement in muscle strength lasting for 6-24 months, whereas only 27% of other sIBM patients improved. All 6 patients with sIBM/SS carried the HLA-DRB1*0301 allele, or its equivalent HLA-DR3 serological specificity, compared with 83% of other sIBM cases and all carried some or all of the major markers of the 8.1 MHC ancestral haplotype which is also associated with Sjögrens syndrome. Patients with sIBM/SS represent a subgroup of sIBM cases who are more likely to be female and carriers of HLA-DR3 and the 8.1 MHC ancestral haplotype, and are more likely to respond to treatment. The association of sIBM and Sjögrens syndrome is likely to be due to a common genetic predisposition linked to the MHC and supports the notion that sIBM has an autoimmune basis.

An analysis of the sensitivity and specificity of MHC-I and MHC-II immunohistochemical staining in muscle biopsies for the diagnosis of inflammatory myopathies

Although there have been several previous reports of immunohistochemical staining for MHC antigens in muscle biopsies, there appears to be a lack of consensus about its routine use in the diagnostic evaluation of biopsies from patients with suspected inflammatory myopathy. Positive MHC-I staining is nonspecific but is widely used as a marker for inflammatory myopathy, whilst the role of MHC-II staining is not clearly defined. We investigated the sensitivity and specificity of MHC-I and MHC-II immunostaining for the diagnosis of inflammatory myopathy in a large group of biopsies from a single reference laboratory. Positive staining for MHC-I was found to have a high sensitivity in biopsies from patients with inflammatory myopathy but a very low specificity, as it was also common in other non-inflammatory myopathies and neurogenic disorders. On the other hand, MHC-II positivity had a much higher specificity in all major subgroups of inflammatory myopathy, especially inclusion body myositis. The findings indicate that the combination of MHC-I and MHC-II staining results in a higher degree of specificity for the diagnosis of inflammatory myopathy and that in biopsies with inflammation, positive MHC-II staining strongly supports the diagnosis of an immune-mediated myopathy. We recommend that immunohistochemical staining for both MHC-I and MHC-II should be included routinely in the diagnostic evaluation of muscle biopsies from patients with suspected inflammatory myopathy. However, as the sensitivity and interpretation of MHC staining may depend on the technique used, further studies are needed to compare procedures in different centres and develop standardised protocols.

Complement-mediated muscle cell lysis: A possible mechanism of myonecrosis in anti-SRP associated necrotizing myopathy (ASANM)

The mechanism of necrotizing myopathy associated with antibodies to signal recognition particle (SRP) remains unclear. We investigated the effect of anti-SRP+serum and complement on cell viability in myoblast cultures. Cell viability was only slightly reduced by incubation with anti-SRP+serum compared with control serum. However, the addition of fresh complement resulted in a marked reduction in cell survival. Surface immunostaining for SRP, C3c and C5b-9 was demonstrated in cultures pre-incubated with anti-SRP+serum and complement, and in muscle biopsies from patients with myopathy. These findings provide further support for a complement-dependent antibody-mediated mechanism in anti-SRP associated myopathy.

Creutzfeldt-Jakob syndrome presenting as epilepsia partialis continua

Creutzfeldt-Jakob disease (CJD) is an uncommon rapidly progressive neurological disorder which can have protean clinical presentations. We report an autopsy-proven case of CJD presenting initially as epilepsia partialis continua but then developing the typical clinical features of CJD over several weeks. CJD should be considered in the differential diagnosis of new onset epilepsia partialis continua in adults.