Case report: Fatal infantile hypertonic myofibrillar myopathy with compound heterozygous mutations in the CRYAB gene

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.

[Study on molecular epidemiological characteristics of influenza H1N1 viruses circulating in Shenzhen, China from 2005 to 2007]

OBJECTIVE

To study the genetic and epidemiological characteristics of HA1 of influenza H1N1 viruses circulating in Shenzhen from 2005 to 2007.

METHODS

The HA1 region was analyzed by RT-PCR and subsequently sequenced to analyze the HA1 genetic evolution. Phylogenetic analysis was confirmed on the homology of nucleotide comparing with the reference viruses of vaccines recommended by WHO and representative virus confirmed by China CDC. Relationship between isolation rates and genetic evolutions was explored.

RESULTS

The average isolation rate from 2005 to 2007 was 7.16%. Of the isolates, the proportions of influenza H1N1 viruses in 2005, 2006 and 2007 were 56.14%, 66.03%, 3.61%, respectively. Data from HA1 phylogenetic analysis showed that there were at least three clades circulated in Shenzhen. Different viruses isolated during January to April were clustered with A/New Caledonia/20/1999 viruses isolated in the latter months of 2005 clustered with A/Solomon Island/3/2006 and viruses from 2006 to 2007 were in the same clade with A/GDLH/219/2006. Results showed that most viruses had a deletion of lysine at position 130. Compared with A/New Caledonia/20/1999, the virus isolated after May of 2005 occurred T82K, Y94H, R146K, R209K, T267N amino acid substitution, while some virus isolated after May 2006 took place the amino acid substitutions of A190T, H193Y, E195D (located at antigenic site B) and R146K (antigenic site A). The sequences at the receptor-binding sites and glycosylation sites were conserved. Compared with referring viruses, A/SZ/68/2007 had 50 amino acid substitutions in the HA1 region. Of these, eleven and six were located at antigenic sites and receptor-binding sites, respectively. Four amino acid substitution resulted in the deletion of glycosylation site.

CONCLUSION

Three different genetic lineages of influenza H1N1 virus were circulated in the population in Shenzhen during 2005 - 2007. The special virus named A/SZ/68/2007 should be paid further attention on its antigenic and epidemiological characteristics.

[Laboratory diagnosis and molecular characterization analysis of the H5N1 influenza virus isolated from the first human case in Shenzhen, China]

The tracheal aspirates and serum samples of a suspected human case of high-pathogenic avian influenza (firstly found in Shenzhen, China) were collected and tested by a series of assays. The results showed that the RNA extracted from the tracheal aspirate specimens of the patient was confirmed positive for H5N1 avian influenza virus by Real-time PCR. The H5N1 avian influenza virus was isolated from patient's tracheal aspirates on MDCK cell and was named A/Guangdong/2/06(H5N1). The viral load of tracheal aspirates collected at different time points were detected by Real-time PCR. The virus microneutralization and the antigenic ratio of human H5N1 isolated were also assayed. It was found that when the virus load decreased gradually after the disease onset, the serum neutralizing antibody titer in the patient increased to 1 : 160 and subsequently decreased gradually. By molecular analysis, the eight gene segments of A/Guangdong/2/06 revealed to be similar to that of H5N1 avian influenza viruses isolated from south China in 2005-2006. However, there were obvious differences in the gene sequence of the detected H5N1 viral RNA as compared with that of the strains isolated from Vietnam, Thailand and Indonesia.