Isolated necrotizing myopathy associated with ANTI-PL12 antibody

Immune-mediated myopathies are a heterogeneous group of chronic autoimmune disorders. Autoantibodies associated with this disease complex are classified into myositis-associated and myositis-specific. Anti-tRNA synthetase antibodies are the most well known of the myositis-specific antibodies. Previous reports have revealed an association of tRNA synthetase autoantibodies with systemic connective tissue disorders.

Our case report involved a 49-year-old man who developed difficulty walking and climbing stairs 5 months prior to his initial visit. No rash or skin changes were observed.

Laboratory testing was positive for anti-PL12 autoantibody with a negative evaluation for connective tissue disorder (CTD). The patient was found to have necrotizing myopathy associated with anti-PL12 antibodies in the absence of inflammatory changes on biopsy, significant derangement of muscle enzymes, or findings characteristic of a typical CTD.

A high index of suspicion must be maintained for immune-mediated necrotizing myopathy despite the absence of an identifiable CTD and milder symptoms.