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Background: Fatal infantile hypertonic myofibrillar myopathy (FIHMM) is an autosomal recessive hereditary disease characterized by amyotrophy, progressive flexion contracture and ankylosis of the trunk and limb muscles, apnea and respiratory failure, and increased creatine phosphate levels. It is caused by mutations in the CRYAB gene, and only around 18 cases including genetic mutations have been reported worldwide. All patients with FIHMM develop respiratory distress, progressive stiffness of the limbs, and have a poor prognosis. However, no effective treatment for CRYAB-associated respiratory failure has been reported. Here, we report a case of FIHMM with a novel heterozygous missense mutation. Case Presentation: A 2-year-old female developed scoliosis of the lumbar spine and restrictive ventilatory dysfunction in infancy. She was admitted to the hospital with labored breathing on the third day after the second injection of inactivated poliomyelitis vaccine. Acute respiratory failure, pneumothorax, and cardiac arrest arose in the patient during hospitalization, and progressive stiffness of the trunk and limb muscles appeared, accompanied by obvious abdominal distension and an increase in phosphocreatine kinase levels. Screenings for genetic metabolic diseases in the blood and urine were normal. Electromyography revealed mild myogenic damage. A muscle biopsy indicated the accumulation of desmin, α-crystallin, and myotilin in the musculus biceps brachii, and dense granules were observed in muscle fibers using electron microscopy. Mutation analysis of CRYAB revealed a novel heterozygous missense mutation in the proband, c.302A > C (p.His101Pro) and c.3G > A (p.Met1Ile), which inherited from her asymptomatic, heterozygous carrier parents, respectively. The proband was finally diagnosed as FIHMM. One month after the FIHMM diagnosis, the child died of respiratory failure. Conclusion: We report a case of FIHMM with a novel heterozygous missense mutation of CRYAB. This finding might improve our understanding of FIHMM and highlight a novel mutation in the Chinese population.
RESUMO
Objective:To investigate the clinical, skeletal muscle pathological, and genetic characteristics of fatal infantile hypertonic myofibrillar myopathy (FIHMM).Methods:The clinical manifestations, laboratory assessments data and gene sequencing results of 10 patients diagnosed with FIHMM in Shenzhen Children′s Hospital from February 2017 to April 2021 were retrospectively analyzed.Magnetic resonance imaging (MRI) of both musculoskeletal system and the brain, and electromyogram (EMG) were performed in 3 cases, while muscle biopsy was performed in 2 cases.Results:Among these 10 cases, 1 case was from Northeast China and 1 case from East China, while the rest 8 cases were from South China.Eight of the 10 patients were male, and the other 2 cases were female.They were all born normal and not related to each other.The age of onset varied from 2 to 12 months.The main clinical manifestations for all the patients were progressive rigidity of the rectus abdominis (8 cases), neck muscles (7 cases), rectus abdominis (2 cases) and intercostal muscles (1 case), resulting in respiratory failure.Mildly to moderately elevated serum creatine kinase level was detected (436-5 804 IU/L) (reference range: 24-229 IU/L). Complex repetitive discharges can be seen in the EMG, without any myotonic potential.Muscle fiber degeneration, necrosis, and vacuolar degeneration were noted in the histopathological examination of the vastus lateralis and rectus abdominis.An abnormal red granular deposit was observed in a portion of the field of the modified Gomory Trichrome staining.Immunohistochemistry showed substantial deposition of desmin.Under the electron microscopy, the sarcomere structure of the muscle fibers was seriously disordered, with the destruction of Z-bands and the presence of granular deposits.The whole-exome sequencing identified the same homozygous variation c. 3G>A, p.Met1? of CRYAB gene in all the patients, but heterozygous variation in their parents. Conclusions:Axial muscles involvement, such as rectus abdominis rigidity, is the main clinical characteristic of FIHMM.c.3G>A, p.Met1? mutation in the CRYAB gene is a hotspot mutation in Chinese children.
