title: Mutations in TPM2 and congenital fibre type disproportion.
abstract: The main diagnostic feature of congenital fibre type disproportion is that type 1 fibres are consistently smaller than type 2 fibres in the absence of other histological abnormalities. Mutations in the TPM3, RYR1 and ACTA1 genes are the most common established genetic causes. There has been one previous report of congenital fibre type disproportion due to a mutation in TPM2, although some atypical histological features were present. We present two cases in which novel de novo missense mutations in TPM2 are associated with marked fibre size disproportion. The finding of typical histological changes of congenital fibre type disproportion in association with a p.Ser61Pro mutation confirms that TPM2 can cause typical congenital fibre type disproportion. Although not seen on light microscopy studies, protein inclusions typical of small 'caps' were found on electron microscopy in a second patient with a p.Ala155Val mutation in TPM2. This case emphasises the importance of electron microscopy in patients with presumed congenital fibre type disproportion, to exclude the presence of caps, nemaline bodies or minicores, which, if present, may be very helpful in guiding genetic analysis.
authors: Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, Sydney, Australia. nigel.clarke@health.nsw.gov.au
authors: Nigel F
authors: NF
authors: Clarke
authors: Leigh B
authors: LB
authors: Waddell
authors: Lilian T L
authors: LT
authors: Sie
authors: Bregje W M
authors: BW
authors: van Bon
authors: Catriona
authors: C
authors: McLean
authors: Damian
authors: D
authors: Clark
authors: Andrew
authors: A
authors: Kornberg
authors: Martin
authors: M
authors: Lammens
authors: Kathryn N
authors: KN
authors: North
mesh_terms: D005820:Genetic Testing; D006801:Humans; D007223:Infant; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology / Q000648:ultrastructure*; D020125:Mutation, Missense / Q000235:genetics*; D020914:Myopathies, Structural, Congenital / Q000235:genetics* / Q000473:pathology; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics; D014335:Tropomyosin / Q000235:genetics*
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; C518659:TPM2 protein, human; D014335:Tropomyosin