Sporadic late onset nemaline myopathy with monoclonal gammopathy of undetermined significance: two cases with long term stability.

Monoclonal gammopathy of undetermined significance (MGUS) associated to sporadic late onset nemaline myopathy (SLONM) is a rare and severely disabling condition of quickly progressive limb girdle acquired myopathy. It is believed by some authors to be due to myotoxicity of light chain deposits. Two female patients were diagnosed with MGUS associated SLONM. In the first case, diagnosis was delayed by 6 years thus giving time for a severe generalized myopathy and cardiomyopathy to develop. A single anti-myeloma chemotherapy with lenalidomide markedly improved and stabilized the patient's condition despite respiratory and cardiac insufficiency. In our second patient the condition was identified one year after onset of the first symptom and markedly improved after autologous bone marrow transplantation and lenalidomide. Clinicians should be aware of monoclonal gammopathy associated sporadic late onset nemaline myopathy as this acquired muscle disorder, although extremely rare, may be reversed by adequate management.

[The role of pathology in neuromuscular diseases]. / Le rôle du pathologiste dans la prise en charge des maladies neuromusculaires.

Myopathies are rare diseases. They may be genetic (muscular dystrophies, metabolic or congenital myopathies) or acquired (inflammatory, drug-related or toxic myopathies and those due to systemic disease). Muscular abnormalities secondary to affections of the peripheral nervous system or anterior horn are not strictly speaking myopathies. Morphological examination of muscle tissue is the key stage of the diagnostic workup, and crucial in directing patient care. Muscle biopsy analysis takes into account clinical and paraclinical data and requires close collaboration between the clinician and pathologist. Three illustrative examples are presented: a congenital muscular dystrophy, a glycogenosis and a muscular dystrophy mimicking polymyositis.

[Sensory neuropathies]. / Neuropathies sensitives.

Peripheral sensory neuropathies are rare. Their clinical and electrophysiological pictures vary mainly with the course of the disorder (acute, subacute or chronic), with the size of the nerve fibres (large or small diameter) and the nervous structure involved (sensory axon or dorsal root ganglion). We discuss the characteristics and aetiologies of the various sensory neuropathies. Clinical case reports underline the practical aspects of these disorders.

Confirmation of the type 2 myotonic dystrophy (CCTG)n expansion mutation in patients with proximal myotonic myopathy/proximal myotonic dystrophy of different European origins: a single shared haplotype indicates an ancestral founder effect.

Myotonic dystrophy (DM), the most common form of muscular dystrophy in adults, is a clinically and genetically heterogeneous neuromuscular disorder. DM is characterized by autosomal dominant inheritance, muscular dystrophy, myotonia, and multisystem involvement. Type 1 DM (DM1) is caused by a (CTG)(n) expansion in the 3' untranslated region of DMPK in 19q13.3. Multiple families, predominantly of German descent and with clinically variable presentation that included proximal myotonic myopathy (PROMM) and type 2 DM (DM2) but without the DM1 mutation, showed linkage to the 3q21 region and were recently shown to segregate a (CCTG)(n) expansion mutation in intron 1 of ZNF9. Here, we present linkage to 3q21 and mutational confirmation in 17 kindreds of European origin with PROMM and proximal myotonic dystrophy, from geographically distinct populations. All patients have the DM2 (CCTG)(n) expansion. To study the evolution of this mutation, we constructed a comprehensive physical map of the DM2 region around ZNF9. High-resolution haplotype analysis of disease chromosomes with five microsatellite and 22 single-nucleotide polymorphism markers around the DM2 mutation identified extensive linkage disequilibrium and a single shared haplotype of at least 132 kb among patients from the different populations. With the exception of the (CCTG)(n) expansion, the available markers indicate that the DM2 haplotype is identical to the most common haplotype in normal individuals. This situation is reminiscent of that seen in DM1. Taken together, these data suggest a single founding mutation in DM2 patients of European origin. We estimate the age of the founding haplotype and of the DM2 (CCTG) expansion mutation to be approximately 200-540 generations.

[How should a muscular disease be studied?]. / Comment investiguer une maladie musculaire?

Muscle diseases are an expanding field, mainly due to the progress in genetics and biochemistry. Evaluation starts with a thorough history of the patient's symptoms and signs. The leading clinical manifestations are weakness, atrophy, myalgia, fatigue, more rarely myotonia and in the child hypotonia or walking difficulty. A detailed family history might give clues to an underlying genetic etiology. Diagnostic workup begins with the measurement of serum creatine kinase. Electroneuromyography is an important investigation procedure which includes motor and sensory nerve conduction studies and concentric needle electromyography. Muscle biopsy is performed in all patients with clinical evidence of myopathy. A fine-needle technique is generally used, more often than a surgical biopsy. Molecular analysis of candidate genes is becoming a major diagnostic tool in many muscle disorders. Muscle imaging, in particular MR, provides diagnostic and follow-up information, especially in dystrophic, metabolic and inflammatory myopathies. Exercise testing can be useful in some metabolic myopathies. There is no standard protocol for the choice and course of investigations which must always be based on a detailed clinical evaluation. It is important to establish a precise diagnosis in order to inform the patient about the nature and the evolution of the disease, the therapeutic options and to propose, when indicated, genetic counseling.