Overview
FKTN encodes fukutin, a glycosyltransferase involved in the glycosylation of alpha-dystroglycan. Mutations in FKTN cause Fukuyama Congenital Muscular Dystrophy (FCMD), the most common form of congenital muscular dystrophy in Japan. The most common mutation is a retrotransposon insertion in the 3′-untranslated region of the gene.
9q31.2 (Chromosome 9)
Hereditary Diseases
Autosomal recessive
Most common muscular dystrophy in Japan (1:10,000), very rare outside Japan
Function & Significance
Fukutin is a glycosyltransferase necessary for the correct glycosylation of dystroglycan. It works in the same glycosylation cascade as POMT1, POMT2, and other dystroglycanopathy genes. The exact biochemical function of fukutin is not yet fully understood, but it is clear that it is essential for the binding of dystroglycan to the extracellular matrix.
The most common mutation in FCMD is a 3-kb retrotransposon insertion that leads to reduced fukutin expression. This founder mutation is responsible for over 80% of all FCMD cases in Japan.
🔬 Fukuyama Congenital Muscular Dystrophy
FCMD was first described in 1960 by Dr. Yukio Fukuyama. It is the second most common muscular dystrophy in Japan after Duchenne muscular dystrophy. The disease is characterized by congenital muscle weakness, intellectual disability, seizures, and brain malformations (polymicrogyria, pachygyria).
Associated Diseases
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🧠 Fukuyama Congenital Muscular Dystrophy (FCMD)
Congenital muscle weakness, intellectual disability, seizures, polymicrogyria. Typical life expectancy is 10-20 years.
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💪 Limb-Girdle Muscular Dystrophy Type 2M (LGMD2M)
Milder form with later onset, normal intelligence, proximal muscle weakness
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🧬 Walker-Warburg Syndrome
Very rare, severe form with lissencephaly and eye anomalies
🧬 Relevant SNPs
The most common mutation in FCMD is a 3-kb retrotransposon insertion in the 3′-UTR of the FKTN gene. This insertion reduces fukutin expression and accounts for over 80% of all FCMD cases in Japan. Other mutations are rarer and include missense, nonsense, and splice-site mutations.
⚕️ Clinical Significance
Diagnosis: Muscle biopsy shows reduced dystroglycan glycosylation. Brain MRI shows characteristic polymicrogyria and pachygyria. Genetic tests confirm FKTN mutations.
Management: Supportive therapy with physical therapy, anticonvulsant medication for seizures, respiratory support, nutritional management. Early intervention for developmental delays.
Prognose: FCMD has a reduced life expectancy. Most patients do not reach adulthood, although some can live longer with good supportive care. Milder forms (LGMD2M) have a better prognosis.
Genetic Counseling: Important for Japanese families with a history of FCMD. Prenatal diagnosis is possible.
📚 Data Sources
The information on this page is based on the following scientific sources:
- OMIM: #607440 (FKTN), #253800 (Fukuyama Congenital Muscular Dystrophy)
- ClinVar: Pathogenic FKTN variants
- PubMed: Literature on Fukuyama Muscular Dystrophy
- Orphanet: ORPHA272 (Fukuyama congenital muscular dystrophy)
Last Update: February 2026