Myopathies associated with β-tropomyosin mutations.

Area of Science:

• Genetics
• Molecular Biology
• Neurology

Background:

• Mutations in the TPM2 gene, which encodes β-tropomyosin, are increasingly recognized as a cause of various muscle disorders.
• Understanding the spectrum of these diseases is crucial for diagnosis and management.

Observation:

• TPM2 mutations manifest heterogeneously, encompassing non-specific congenital myopathy with type 1 fiber predominance, nemaline myopathy, cap disease, and distal arthrogryposis.
• Escobar syndrome with nemaline myopathy is linked to homozygous truncating β-tropomyosin mutations.
• Cap disease is the most frequent morphological finding, often accompanied by a coarse intermyofibrillar network and jagged Z lines.

Findings:

• Dominant TPM2 mutations present as either congenital myopathy (typically with moderate weakness and no contractures) or distal arthrogryposis (characterized by hand/foot contractures and mild weakness).
• The specific type or location of TPM2 mutations does not correlate clearly with the clinical or morphological phenotype.
• Homozygous truncating mutations are associated with Escobar syndrome and nemaline myopathy.

Implications:

• This review consolidates the understanding of β-tropomyosin-associated diseases, emphasizing their clinical and morphological variability.
• Identifying novel mutations and characterizing their impact aids in diagnosing and potentially treating a range of neuromuscular conditions.
• Further research may elucidate genotype-phenotype correlations and inform therapeutic strategies for TPM2-related myopathies.