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Título

Centronuclear myopathy: case report

RESUMO

Female, 47-year-old, previously healthy, started at age 23 with a condition of distal, progressive and mild weakness in the lower limbs, with stumbling and falls, but without limitations in activities of daily living. After the age of 40, she began to have difficulty climbing stairs and getting up from chairs, in addition to being unable to carry bags or purses anymore. No report of bulbar symptoms. Past history: no comorbidities.
Family history: mother and younger brother (40 years old) with similar neurological picture. Neurological examination shows mild eyelid ptosis, especially on the right. facial diparesis. Divergent strabismus evident in the right eye. Muscle strength by the Medical Research Council Scale demonstrating grade 4 in the upper and lower limbs distally, Grade 3 in foot dorsiflexion and grade 4 in flexion. Grade 4 quadriceps and bilateral gluteus medius. Muscle hypotonia. Grade 1 deep reflexes globally except for abolished Achilles reflexes, bilateral Achilles tendon retraction, bilateral cutaneous-plantar flexion reflex. No winged scapula. Absence of myotonic phenomena. Sensitivity preserved. Myopathic gait, not walking on tiptoes and heels. Laboratory tests demonstrate CPK at normal levels. ENMG (2021): signs of primary muscle fiber involvement, associated with signs of active denervation in most motor units examined, predominantly proximal and lower limbs.Genetic Testing: Identified heterozygous pathogenic variant DNM2 c.1393C>T (p. Arg465Trp).
Discussion
Mutations in the DNM2 gene lead to congenital centronuclear myopathy (CCM) and two forms of Charcot-Marie-Tooth (CMT) in the autosomal dominant form. NCM manifests as a disorder of progressive deterioration and delays in motor milestones, facial and generalized muscle weakness, ptosis, and ophthalmoplegia. Some patients also develop pes cavus before experiencing symptomatic muscle weakness. CNM patients with DNM2 mutations had mild axonal neuropathy, which may or may not have reduced motor conduction velocities.
Final comments
This case illustrates a patient with late-onset and slowly progressive Centronuclear Myopathy, associated with pes cavus and global hyporeflexia, with normal levels of CPK, ENMG with myopathic pattern and confirmed by genetic testing.