Juvenile Autoimmune Necrotizing Myopathies

Clinical, Paraclinical, Functional Characteristics and Evolution of Juvenile Autoimmune Necrotizing Myopathies in a National Retrospective Cohort

Autoimmune necrotizing myopathies (AINM) in adult patients are characterized by severity of muscle damage, presence of necrosis with little inflammation on muscle biopsy and anti-HMGCR or anti-SRP auto-antibodies. Data on AINM in children are currently lacking. The purpose of this study is to specify the characteristics at AINM diagnosis, treatments and evolution of juvenile AINM with anti-HMGCR or anti-SRP antibodies.

Inclusion Criteria:

• AINM histologically proved by predominant muscle fibers necrosis lesions associated with minimal or absent inflammatory lesions
• Either anti-SRP or anti-HMGCR antibodies positivity
• Disease onset before age 18

Exclusion Criteria:

• Seronegative necrotizing myopathies
• Forms compatible with another type of myositis (e.g. dermatomyositis)