Merosindeficient

Merosindeficient is a term used in some medical texts to describe a deficiency or loss of function of merosin, the basement membrane protein laminin subunit alpha-2 (LAMA2). Merosin is a component of the skeletal muscle extracellular matrix and is essential for the stability of muscle fibers. Deficiency can arise from biallelic mutations in the LAMA2 gene or from acquired downregulation of merosin expression, and it is most often discussed in relation to congenital muscular dystrophy.

Clinical presentation typically includes hypotonia and delayed motor development from birth or infancy, progressive proximal weakness, orthopedic deformities, and respiratory muscle involvement. Laboratory findings often include elevated serum creatine kinase, and brain MRI may show white matter changes in more severe cases.

Diagnosis is supported by reduced or absent merosin staining on muscle biopsy and confirmed by genetic testing revealing LAMA2 mutations.

Management is multidisciplinary and focuses on maintaining mobility and respiratory function through physical therapy, orthopedics, respiratory support, nutrition, and supportive devices; there is no approved disease-modifying therapy. Research into targeted therapies, including gene-based approaches for LAMA2, is ongoing.

Prognosis is highly variable, with severe neonatal forms limiting mobility and milder forms showing slower progression.

Related conditions include merosin-deficient congenital muscular dystrophy and other LAMA2-related muscular dystrophies.