CARE-compliant case report: Nemaline myopathy caused by the ACTA1 p.Q139H missense mutation

Nemaline myopathy (NM) is a rare inherited muscle disorder characterized by nemaline rods in muscle fibers and clinically presenting with muscle weakness and hypotonia. This report describes a case of NM caused by a mutation in the ACTA1 (actin alpha 1) gene to enhance the understanding of its diagnosis and clinical course, particularly in the context of pregnancy.

A 33-year-old female presented with progressive lower limb weakness and muscle atrophy. Symptom onset occurred during pregnancy. Laboratory tests revealed an elevated serum creatine kinase level (1011 U/L).

Genetic testing identified a heterozygous missense mutation (Q139H, c.417G>C) in exon 3 of the ACTA1 gene, confirming the diagnosis of NM. A muscle biopsy to definitively identify nemaline rods was indicated but was declined by the patient.

The diagnostic evaluation included clinical examination, serum creatine kinase testing, electromyography, and genetic analysis. Following diagnosis, the patient was managed with a regimen of supportive care.

Electromyography confirmed myopathic changes. With supportive care, the patient remained clinically stable at follow-up.

This case underscores the diagnostic utility of genetic testing for NM when a muscle biopsy is not feasible. It also demonstrates the potential for symptom exacerbation or onset during pregnancy and highlights the importance of multidisciplinary supportive care and genetic counseling in the management of ACTA1-related NM.