Rare case of congenital myopathy associated with the FXR1 gene

Case presentation: A.M.M., 14 years old, consanguineous parents; term, pregnancy and delivery without complications, mother without history of abortion. Healthy parents, 19-year-old sister and healthy 12-year-old brother. At 4 months, the mother noticed the absence of head support, difficulty in sucking and swallowing. She evolved with repeated hospitalizations due to aspiration pneumonia. At 10 months she sat up with support; she did not crawl and at 15 months walked with support. She acquired independent gait at 2 years of age, but had many falls, stood up with the help of her arms and did not climb steps. Cognitive apparently preserved. At age 5, she was often tired on short-distance walks and needed bipap assistance during sleep. She was always carried by her parents to get around, due to weakness and frequent falls, so at age 7 she started using a wheelchair. She did not eat solid food due to choking. At 8 years old, she started to eat only through a gastrostomy. At 10 years of age, she had scoliosis and significant lordosis, winged scapula, axial and appendicular hypotonia, dropped head, grade 2 muscle strength in the proximal upper limb and distal lower limb, grade 3 in the distal upper limb and proximal lower limb. Hypoactive osteotendinous reflexes, without signs of pyramidal release. Broad DNA panel for neuromuscular diseases was requested, and a rare mutation was identified in the FXR1 gene in homozygosis.

Discussion: Homozygous pathogenic variants in the FXR1 gene were associated with 2 phenotypes: congenital myopathy with respiratory failure and bone fractures characterized by a very early and severe myopathy leading to hypotonia, dysphagia, respiratory failure and fracture of long bones. Another phenotype presents as congenital myopathy with “minicore” lesions, which has an early onset and mainly affects the proximal muscles. It is characterized by muscle weakness, hypotonia and delay in gait acquisition, slowly progressive course, difficulty running and climbing stairs. There is no cardiac involvement, but obstructive sleep apnea may occur. The patient described presented early manifestation and progressive evolution, with gait delay, loss of strength to stand and walk, swallowing difficulty requiring gastrostomy and obstructive sleep apnea.

Final comments: The patient described has a congenital myopathy phenotype with minicore lesions. This condition was previously described in the medical literature in only two families, hence the importance of this report.

 

MissingLinkText

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
18 September 2023