Table 1.

Summary of Molecular Genetic Testing Used in Fukuyama Congenital Muscular Dystrophy

Gene 1Test MethodAllelic Variants Detected 2Variant Detection Frequency by Test Method 3
JapaneseNon-Japanese
FKTNTargeted analysis for pathogenic variantsc.*4287_*4288ins3062 4See footnote 5See footnote 6
Sequence analysis of coding and flanking intronic regionsSequence variants 7See footnotes 8, 9
Sequence analysis of cDNA or targeted intronic sequencing 10mRNA variants, particularly intronic variants with splicing effects (e.g., pseudoexon mutation 11)UnknownSee footnote 6
1.
2.

See Molecular Genetics for information on allelic variants.

3.

The ability of the test method used to detect a variant that is present in the indicated gene

4.

A. c.*4287_*4288ins3062, a 3-kb retrotransposonal insertion of tandemly repeated sequences into the 3' untranslated region of FKTN, is a Japanese founder variant [Kato et al 2004].

5.

In an analysis of 117 Japanese individuals with FCMD: 94 (80%) were homozygous for the founder variant; 17 (15%) were compound heterozygous for the founder variant and an identifiable single-nucleotide variant on the second allele (of the 17, 14 had the pathogenic nonsense variant p.Arg47Ter, two had the pathogenic missense variant p.Cys250Gly, and one had the pathogenic missense variant p.His172Arg in exon 5); and six (5%) were compound heterozygotes for the founder variant and an unidentified pathogenic variant on the second allele [Saito, in preparation].

6.

Molecular genetic testing confirmed the clinical diagnosis of FCMD in 13 individuals of Korean heritage: two were homozygous for the Japanese founder retrotransposal insertion variant; of the seven who were compound heterozygous for the retrotransposal insertion variant, five had the novel intronic variant (c.647+2084G>T) that is specific to the Korean population [Lim et al 2010].

7.

Examples of pathogenic variants detected by sequence analysis may include small intragenic deletions/insertions and missense, nonsense, and splice site variants; typically, exon or whole-gene deletions/duplications are not detected. For issues to consider in interpretation of sequence analysis results, click here.

8.

Silan et al [2003] and de Bernabe et al [2003] independently reported two Turkish individuals with FCMD with an extremely severe phenotype that resembled Walker-Warburg syndrome (WWS) with homozygous pathogenic FKTN nonsense variants on both alleles.

9.

Chang et al [2009] reported c.1167_1168insA as a founder variant in Ashkenazi Jews with FCMD.

10.

From muscle or lymphocytes

11.

Lim et al [2010] reported a novel pathogenic variant (c.647+2084G>T; p.Arg216SerfsTer10) that is specific to the Korean population. In this variant a single base-pair change activates a pseudoexon between exon 5 and 6.

From: Fukuyama Congenital Muscular Dystrophy

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