HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Data Supplement Correspondence: Submit a response Alert me when this article is cited Alert me when Correspondence are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Hicks, D. Articles by Bushby, K. PubMed PubMed Citation Articles by Hicks, D. Articles by Bushby, K.

A refined diagnostic algorithm for Bethlem myopathy

From the Institute of Human Genetics (D.H., A.K.L., C.F., H.L., V.S., K.B.), Newcastle University, Newcastle upon Tyne, UK; Muscle Immunoanalysis Unit (R.B., R.C.) and Northern Region Genetics Service (J.H., R.S.), Newcastle upon Tyne NHS Trust, UK; and Division of Neurology (C.G.B.), The Children’s Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, PA.

Address correspondence and reprint requests to Prof. K. Bushby, Institute of Human Genetics, International Centre for Life, Central Parkway, Newcastle upon Tyne, NE1 3BZ, Great Britain

Objective: Mutations in COL6A1, COL6A2, and COL6A3, the genes that encode the extracellular matrix component collagen VI, lead to Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD). Unlike UCMD, BM is difficult to diagnose because of its clinical overlap with other contractural phenotypes and the lack of sensitivity of standard muscle biopsy immunohistochemical diagnostic techniques.

Methods: We appraised two potential techniques for the diagnosis of BM: dual immunofluorescence (IF) for collagen VI and basal lamina–located perlecan in muscle, and immunofluorescent labeling of collagen VI in skin biopsy–derived fibroblast cultures, which was conducted in 40 patients by blinded investigators and correlated with genetic findings.

Results: Dual IF was indistinguishable from normal controls in most BM patients. However, abnormalities in the IF labeling pattern of collagen VI were detected in more than 78% of genetically confirmed BM patient fibroblast cell lines. In addition, in a group of patients with unknown diagnosis studied prospectively, the fibroblast IF technique was highly predictive of the presence of a COL6A mutation, providing a positive predictive value of 75%, a sensitivity and negative predictive value of 100%, and a specificity of 63%.

Conclusions: Immunofluorescent labeling of collagen VI in fibroblast cultures is a useful addition to current diagnostic services for Bethlem myopathy (BM). It can be used to guide molecular genetic testing, the gold standard diagnostic technique for BM, in a cost-effective and time-saving manner.

Abbreviations: BM = Bethlem myopathy; cDNA = complementary DNA; DAPI = 6-diamidino-2-phenylindole; FITC = fluorescein isothiocyanate; IF = immunofluorescence; IHC = immunohistochemistry; mRNA = messenger RNA; NA = not applicable; PBS = phosphate-buffered saline; PTC = premature termination codon; UCMD = Ullrich congenital muscular dystrophy.

Supplemental data at www.neurology.org

*These authors contributed equally to this work.

Supported by a Muscular Dystrophy Campaign grant (K.B.), Muscular Dystrophy Campaign of Great Britain and TREAT-NMD (EC, 6th FP, proposal 036825; www.treat-nmd.eu), a Wellcome entry level fellowship (A.K.L.), a Patrick Berthoud fellowship (A.K.L.), and grants from MDA USA (MDA3896) and NIH/NIAMS (R01AR051999) (C.G.B). Diagnostic facilities at the Newcastle Muscle Centre are supported by the National Commissioning Group for Rare Neuromuscular Disorders.

Disclosure: The authors report no conflicts of interest.

Received August 21, 2007. Accepted in final form December 12, 2007.