New cardiac and skeletal protein aggregate myopathy associated with combined MuRF1 and MuRF3 mutations.

Protein aggregate myopathies (PAMs) define muscle disorders characterized by protein accumulation in muscle fibres. We describe a new PAM in a patient with proximal muscle weakness and hypertrophic cardiomyopathy, whose muscle fibres contained inclusions containing myosin and myosin-associated proteins, and aberrant distribution of microtubules. These lesions appear as intact A- and M-bands lacking thin filaments and Z-discs. These features differ from inclusions in myosin storage myopathy (MSM), but are highly similar to those in mice deficient for the muscle-specific RING finger proteins MuRF1 and MuRF3. Sanger sequencing excluded mutations in the MSM-associated gene MYH7 but identified mutations in TRIM63 and TRIM54, encoding MuRF1 and MuRF3, respectively. No mutations in other potentially disease-causing genes were identified by Sanger and whole exome sequencing. Analysis of seven family members revealed that both mutations segregated in the family but only the homozygous TRIM63 null mutation in combination with the heterozygous TRIM54 mutation found in the proband caused the disease phenotype. Both MuRFs are microtubule-associated proteins localizing to sarcomeric M-bands and Z-discs. They are E3 ubiquitin ligases that play a role in degradation of sarcomeric proteins, stabilization of microtubules and myogenesis. Lack of ubiquitin and the 20S proteasome subunit in the inclusions found in the patient suggested impaired turnover of thick filament proteins. Disruption of microtubules in cultured myotubes was rescued by transient expression of wild-type MuRF1. The unique features of this novel myopathy point to defects in homeostasis of A-band proteins in combination with instability of microtubules as cause of the disease.

Clinical and myopathological evaluation of early- and late-onset subtypes of myofibrillar myopathy.

Myofibrillar myopathies (MFM) are a group of disorders associated with mutations in DES, CRYAB, MYOT, ZASP, FLNC, or BAG3 genes and characterized by disintegration of myofibrils and accumulation of degradation products into intracellular inclusions. We retrospectively evaluated 53 MFM patients from 35 Spanish families. Studies included neurologic exam, muscle imaging, light and electron microscopic analysis of muscle biopsy, respiratory function testing and cardiologic work-up. Search for pathogenic mutations was accomplished by sequencing of coding regions of the six genes known to cause MFM. Mutations in MYOT were the predominant cause of MFM in Spain affecting 18 of 35 families, followed by DES in 11 and ZASP in 3; in 3 families the cause of MFM remains undetermined. Comparative analysis of DES, MYOT and ZASP associated phenotypes demonstrates substantial phenotypic distinctions that should be considered in studies of disease pathogenesis, for optimization of subtype-specific treatments and management, and directing molecular analysis.

Phenotypic patterns of desminopathy associated with three novel mutations in the desmin gene.

Desminopathy represents a subgroup of myofibrillar myopathies caused by mutations in the desmin gene. Three novel disease-associated mutations in the desmin gene were identified in unrelated Spanish families affected by cardioskeletal myopathy. A selective pattern of muscle involvement, which differed from that observed in myofibrillar myopathy resulting from mutations in the myotilin gene, was observed in each of the three families with novel mutations and each of three desminopathy patients with known desmin mutations. Prominent joint retractions at the ankles and characteristic nasal speech were observed early in the course of illness. These findings suggest that muscle imaging in combination with routine clinical and pathological examination may be helpful in distinguishing desminopathy from other forms of myofibrillar myopathy and ordering appropriate molecular investigations.

Pure sensory neuropathy in primary Sjögren's syndrome. Longterm prospective followup and review of the literature.

OBJECTIVE: To study the clinical course, response to therapy, and longterm outcome of pure sensory neuropathy (PSN) in a series of patients with primary Sjögren's syndrome (SS) followed prospectively in our referral centers. METHODS: We studied 15 patients (13 women, 2 men) with primary SS and PSN. All patients fulfilled 4 or more of the European diagnostic criteria. RESULTS: At diagnosis of PSN, clinical manifestations included numbness and paresthesias (11 patients), trigeminal neuropathy (6 patients), and Adie's pupil syndrome (4 patients). In 7 patients, PSN was diagnosed prior to SS, in 5 the diagnoses were made simultaneously, and in the remaining 3 patients PSN was diagnosed after the appearance of SS symptomatology. The mean duration of the prospective PSN followup was 10 years (range 1-20). The progression of PSN was acute in 1 patient (producing severe dysfunction in less than 1 month), subacute in 3 patients, and in the remaining 11, the symptoms progressed slowly over the ensuing years to other extremities. Patients were treated with corticosteroids (n = 13), cyclophosphamide (n = 4), and intravenous immunoglobulins (n = 1), and 2 patients received no treatment. In spite of treatment, most patients showed an indolent and insidious longterm PSN course. CONCLUSION: We found 3 differentiated clinical courses of the PSN in patients with primary SS: subacute progression in less than 1 month (7%), late acceleration of PSN 2-4 years after an initial indolent onset (20%), and a very longterm insidious, chronic evolution (73%). Prospective analysis of the longterm course of PSN shows a chronic and insidious evolution in most patients with PSN and SS, with a poor response to treatment, although stabilization of symptomatology for long periods is often observed.