Evaluation of the facioscapulohumeral muscular dystrophy (FSHD1) phenotype in correlation to the concurrence of 4q35 and 10q26 fragments

Chronic Myopathy Associated With Anti-Signal Recognition Particle Antibodies Can Be Misdiagnosed As Facioscapulohumeral Muscular Dystrophy

OBJECTIVES

To report cases of chronic autoimmune necrotizing myopathy with anti-signal recognition particle antibodies (anti-SRP myopathy) initially misdiagnosed as muscular dystrophy, in particular, facioscapulohumeral muscular dystrophy (FSHD).

METHODS

Medical records of patients with anti-SRP myopathy in our institution were retrospectively reviewed.

RESULTS

All 6 patients were initially diagnosed with muscular dystrophy because of the long-term clinical course and lack of inflammation on biopsy; 5 were diagnosed with FSHD based on a winged scapula. However, the following features suggested an alternative diagnosis, leading to anti-SRP antibody measurement: (1) lack of family history, (2) lack of facial involvement and asymmetry, (3) prominent dysphagia, and (4) profuse spontaneous activities on needle electromyography. All patients showed improvement with immunomodulating therapy.

CONCLUSIONS

Anti-SRP antibody measurement should be considered in patients diagnosed with FSHD if they present with diagnostic hallmarks of anti-SRP myopathy listed above, to avoid oversight of this potentially treatable disorder.

Evidence-based guideline summary: Evaluation, diagnosis, and management of facioscapulohumeral muscular dystrophy: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology and the Practice Issues Review Panel of the American Association of Neuromuscular & Electrodiagnostic Medicine

OBJECTIVE

To develop recommendations for the evaluation, diagnosis, prognostication, and treatment of facioscapulohumeral muscular dystrophy (FSHD) from a systematic review and analysis of the evidence.

METHODS

Relevant articles were analyzed in accordance with the American Academy of Neurology classification of evidence schemes for diagnostic, prognostic, and treatment studies. Recommendations were linked to the strength of the evidence and other factors.

RESULTS AND RECOMMENDATIONS

Available genetic testing for FSHD type 1 is highly sensitive and specific. Although respiratory insufficiency occurs rarely in FSHD, patients with severe FSHD should have routine pulmonary function testing. Routine cardiac screening is not necessary in patients with FSHD without cardiac symptoms. Symptomatic retinal vascular disease is very rare in FSHD. Exudative retinopathy, however, is potentially preventable, and patients with large deletions should be screened through dilated indirect ophthalmoscopy. The prevalence of clinically relevant hearing loss is not clear. In clinical practice, patients with childhood-onset FSHD may have significant hearing loss. Because undetected hearing loss may impair language development, screening through audiometry is recommended for such patients. Musculoskeletal pain is common in FSHD and treating physicians should routinely inquire about pain. There is at present no effective pharmacologic intervention in FSHD. Available studies suggest that scapular fixation is safe and effective. Surgical scapular fixation might be cautiously offered to selected patients. Aerobic exercise in FSHD appears to be safe and potentially beneficial. On the basis of the evidence, patients with FSHD might be encouraged to engage in low-intensity aerobic exercises.

CALCYON gene variation, schizophrenia, and cocaine dependence

Calcyon is a brain-specific D1 dopamine receptor-interacting protein, with a potential role in D1-mediated physiological processes, including motor control, reward mechanisms, and cognitive processes. Our objective was to investigate the relationship between polymorphism of the CALCYON gene and (1) schizophrenia and (2) cocaine dependence in African-American (AA) and European-American (EA) subjects. Two single nucleotide polymorphisms (SNPs) at the CALCYON locus were genotyped in 70 AA and 206 EA individuals with schizophrenia and 90 AA and 118 EA individuals with cocaine dependence. The control group was comprised of 46 AA and 207 EA subjects screened to exclude those with psychiatric or substance use disorders. The specific polymorphisms studied were markers +295214G/A and +297151T/G. Comparisons of allele and haplotype frequencies between cases and controls were performed with the Fisher's Exact Test. Linkage disequilibrium (LD) between these two SNPs was calculated with the 3LOCUS program. No alleles or haplotypes were found to be associated with schizophrenia or cocaine dependence either in AA or EA subjects. The markers +295214G/A and +297151T/G are in the same haplotype block in all subgroups. Allele and haplotype frequencies differed significantly between EA and AA subjects. These results suggest that these two genetic variants in the CALCYON gene do not play a major role in predisposition to either schizophrenia or cocaine dependence in AA or EA subjects. Furthermore, these findings begin to establish a haplotype map for this gene in the AA and EA populations.

Facioscapulohumeral muscular dystrophy with EcoRI/BlnI fragment size of more than 32 kb

Facioscapulohumeral muscular dystrophy (FSHD) is associated with the deletion of a variable number of 3.3-kb subunits of a tandemly arranged repeat (D4Z4) on chromosome 4q35. EcoRI/BlnI fragments in the range of 10-35 kb are currently defined as disease-associated. Diagnosis of FSHD is frequently complicated by interchromosomal exchange with a homologous locus on 10q26. We present clinical and laboratory data of six subjects from two unrelated families with a marked FSHD phenotype and EcoRI/BlnI fragments of 39 and 33 kb, respectively. Origin on chromosome 4q35 was confirmed by haplotype analysis in the first family and was supported by pulsed field gel electrophoresis data in the second family. Our data further confirm the existence of a region of overlap of normal and pathological fragments. Fragments from this region can obviously be associated with marked FSHD phenotypes. Furthermore, application of linked markers and resolution of all EcoRI/BlnI fragments by pulsed field gel electrophoresis in addition to routine laboratory tests considerably augments the information obtained from molecular tests, upon which genetic counselling can then be based.

Diagnosis of pediatric neuromuscular disorders in the era of DNA analysis

Extraordinary breakthroughs in the molecular pathogenesis of muscle and nerve disease have resulted in an evolving genetic classification of neuromuscular disorders and the development of new diagnostic methods. This remarkable progress has introduced new genetic tests and has changed the indications for use of certain invasive diagnostic procedures in the evaluation of children with presumed disorders of the motor unit. In this review, we present the current diagnostic approach to the more common neuromuscular diseases of infancy and childhood and define the diagnostic role of muscle biopsy and pediatric electromyography/nerve conduction studies in the era of genetic analysis.

An inherited 4q35-EcoRI-DNA-fragment of 35 kb in a family with a sporadic case of facioscapulohumeral muscular dystrophy (FSHD)

We present a case of an adult male patient showing clinical, neurophysiological and histological signs consistent with the phenotype of facioscapulohumeral muscular dystrophy. On molecular testing with a 4q35-DNA-probe p13E-11 (D4F104S1), the patient, his clinically unaffected mother and two sisters shared a 4q35-EcoRI-DNA-fragment of 35 kb on the transition between FSHD1A-associated and polymorphic fragments. Explanatory hypotheses, such as reduced penetrance in females or a phenotype unlinked to the 4q35-locus are considered. Alternatively, additional changes in the unidentified FSHD1A gene could have caused the phenotype. Thus, in such rare cases, the diagnostic evidence of 4q35-EcoRI-fragments is still limited.