Histopathologic changes in the extraocular muscle in centronuclear myopathy with a Dynamin 2 mutation

Area of Science:

• Neuromuscular Disorders
• Ophthalmology
• Genetics

Background:

• Centronuclear myopathy (CNM) is a rare inherited neuromuscular disorder.
• It is characterized by centrally placed nuclei in striated muscle fibers.
• This study investigates histological changes in extraocular muscles (EOM) of a CNM patient with a DNM2 gene mutation.

Observation:

• A 33-year-old female with CNM presented with new-onset strabismus (diplopia and exotropia).
• Her past medical history included lower extremity weakness diagnosed in her late 20s.
• Histopathological analysis of resected EOM revealed mild changes, with 17% centrally located nuclei.

Findings:

• Genetic analysis identified a heterozygous R369W mutation in the Dynamin 2 (DNM2) gene.
• Immunohistochemistry showed normal DNM2 protein distribution in the EOM.
• The EOM exhibited variable fiber size and normal ultrastructure despite the CNM diagnosis.

Implications:

• Mild histological alterations in EOM correlate with mild functional deficits in CNM patients.
• Ophthalmologists should consider CNM in the differential diagnosis for patients with strabismus and a history of myopathy.
• Confirmation can be achieved through muscle biopsy and mutational analysis for DNM2 mutations.