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X-linked myotubular myopathy: a case report of prenatal and perinatal aspects
R W Tyson1, S P Ringel, D K Manchester
1Department of Pediatrics, University of Louisville, Kentucky.
Insights
Severe X-linked myotubular myopathy in male newborns can present in utero with cardiac arrhythmias and respiratory failure. This study highlights potential fatty acid oxidation abnormalities in this rare congenital myopathy.
Area of Science:
- Genetics
- Neurology
- Pediatrics
Background:
- X-linked myotubular myopathy (XLMTM) is a severe congenital neuromuscular disorder primarily affecting males.
- Limited understanding exists regarding the biochemical basis and prenatal progression of XLMTM.
Observation:
- A family with a male infant presenting with in utero polyhydramnios, reduced fetal movement, and cardiac arrhythmias.
- The infant experienced severe respiratory insufficiency postnatally, leading to death.
- Maternal family history included two previous perinatal male deaths.
Findings:
- Postmortem examination revealed generalized muscle wasting, cardiac enlargement, cryptorchidism, and flexion contractures.
- Muscle pathology showed hypotrophic, predominantly Type I fibers with centrally located nuclei and perinuclear clear zones.
- Serum organic acid analysis indicated a significant octanoic acid peak, despite normal liver acyl-CoA dehydrogenase activity.
- Muscle biopsies from the mother and maternal aunt showed increased centrally located nuclei.
Implications:
- This case reinforces the typical clinical and pathological features of severe X-linked myotubular myopathy.
- It confirms prenatal detection of cardiac arrhythmias in affected fetuses.
- The findings suggest a potential abnormality in fatty acid oxidation, warranting further investigation in XLMTM.
Abstract:
Nine families have been reported in which male newborns presented with X-linked myotubular (centronuclear) myopathy. Little is known about the biochemical basis of this disorder or about its natural history in utero. We report a family in which an infant with myotubular myopathy presented in utero with polyhydramnios, poor fetal movement, and fetal cardiac arrhythmias. Shortly after birth the infant died from severe respiratory insufficiency. Gas chromatography-mass spectrophotometry for serum organic acids showed a large octanoic acid peak, but total acyl-CoA dehydrogenase activities in liver were normal. The maternal family history was significant for two perinatal male deaths. Postmortem examination revealed generalized muscle wasting, cardiac enlargement, cryptorchidism, and flexion contractures. Examination of muscle showed numerous fibers that had enlarged, centrally located nuclei and perinuclear clear zones. The muscle fibers were hypotrophic and predominantly of type I. Biopsy specimens of the muscles of the mother and maternal aunt had increased numbers of centrally located nuclei. Neurologic examination was normal. The case demonstrates the typical clinical course, pathology, and family history of severe X-linked myotubular myopathy. In addition, it confirms the reported detection of fetal cardiac arrhythmias and documents what may be an abnormality in fatty acid oxidation.