Genomic coordinate 9:105,558,180
Here I present: “Fukuyama Muscular Dystrophy”, Victor McKusick, Mendelian Inheritance in Man’, 1966. (FKTN). icd10=G71.036
INTRODUCTION.
There are over thirty (30>) types of muscular dystrophy.
Muscular dystrophy is a group of genetic diseases that cause progressive muscle weakness and degeneration. Symptoms include difficulty walking, falling frequently, and problems with motor skills, with the specific symptoms and progression depending on the type of muscular dystrophy. While there is no cure, treatments can help manage symptoms and improve quality of life.
Fukuyama Muscular Dystrophy is an inherited form of congenital muscular dystrophy that primarily affects the muscles, brain, and eyes. It is most common in Japan, but cases have been reported worldwide.
GENETIC CAUSE:
Gene involved: FKTN (fukutin gene).
Cytogenetic location: 9q31.2
Inheritance pattern: Autosomal recessive
PATHOPHYSIOLOGY:
The FKTN gene mutation leads to abnormal glycosylation of α-dystroglycan, a protein essential for linking muscle fibers to the extracellular matrix.
Defective glycosylation causes fragile muscle cell membranes → progressive muscle weakness
It also affects brain development (cobblestone lissencephaly) and eye structure.
CLINICAL FEATURES:
1. Onset: Present from birth or early infancy.
2. Muscle Hypotonia (“floppy infant”), delayed motor milestones, generalized weakness, joint contractures.
3. Neurologic Developmental delay, intellectual disability, seizures, structural brain malformations (cerebral cortex and cerebellum).
4. Ocular Myopia, retinal dysplasia, optic nerve abnormalities.
5. Feeding difficulties.
6. Respiratory issues in severe cases.
There is evidence that Fukuyama muscular dystrophy is caused by mutation in fukutin enzyme (FKTN) gene encoded on cytogenetic location 9q31.2 and genomic coordinate 9:105,558,180.
The fukutin enzyme is primarily active in the heart, brain, and skeletal muscles, and is located within the cell’s Golgi apparatus. Its function is to add ribitol phosphate molecules to the alpha-dystroglycan protein, a process called glycosylation. This modification is critical for alpha-dystroglycan to function correctly as an anchor between the cell’s internal structure and the extracellular matrix (the network of molecules providing structural support outside the cell).
In muscles, functional alpha-dystroglycan helps stabilize and protect muscle fibers, preventing damage during contraction and relaxation.
In the brain, it helps guide the migration of nerve cells (neurons) during early development.
