Immune‑mediated necrotizing myopathy complicated by rhabdomyolysis syndrome and central nervous system cytomegalovirus infection: A case report

Immune-mediated necrotizing myopathy (IMNM) complicated by rhabdomyolysis (RM) syndrome and central nervous system (CNS) infection is extremely rare, difficult to diagnose and associated with a poor prognosis.The present study reports a case of anti-signal recognition particle (anti-SRP) antibody-positive IMNM complicated by RM and CNS cytomegalovirus (CMV) infection to provide a reference for its clinical diagnosis and treatment.The clinical data, laboratory findings, muscle pathology, imaging findings and electromyography results are retrospectively analyzed for a 19-year-old female patient who presented with progressive fatigue and muscle weakness, and the case is discussed in the context of the relevant literature.The patient's serum creatine kinase level peaked at 32,213 U/l, and anti-SRP antibodies were positive.Muscle biopsy revealed myogenic damage with muscle fiber necrosis and C5b-9 deposition.The diagnosis of IMNM was confirmed by muscle biopsy and strongly positive anti-SRP antibodies.Metagenomic next-generation sequencing of the cerebrospinal fluid detected CMV with a relative abundance of 100%; however, viral load quantification and read numbers were not available from the assay.Serum CMV-immunoglobulin (Ig)M (213.30AU/ml; positive) and CMV-IgG (>1,000.00AU/ml; positive) further supported active CMV infection.The patient's muscle strength progressively improved following combined immunotherapy, antiviral therapy and supportive care.At the 6-month follow-up, upper limb muscle strength had recovered to grade 4+, while lower limb muscle strength had recovered to grade 3.In conclusion, for patients presenting with rapidly progressive muscle weakness and increased muscle enzyme levels, myositis-specific antibodies should be tested for as early as possible.When complicated by a CNS infection, differentiation from Guillain-Barré syndrome is essential.Early comprehensive immunotherapy combined with antiviral therapy may improve the prognosis.