Tansley et al reported a rare juvenile idiopathic inflammatory myopathy (JIIM) with autoantibodies against HMGCR. This group of patients is phenotypically distinct. The authors are from the Royal National Hospital for Rheumatic Diseases, University of Bath, University College London, Great Ormond Street Hospital, Leeds Children's Hospital and Nottingham University Hospitals in England.
HMGCR = 3-hydroxy-3-methylglutaryl-CoA reductase
Clinical features:
(1) no or minimal skin rash
(2) significant muscle disease with proximal muscle weakness
(3) poor response to standard therapies
(4) need for early initiation of aggressive therapies
Laboratory findings:
(1) persistent and often marked elevations in serum CK concentration
(2) autoantibodies to HMGCR
Muscle biopsy shows:
(1) wide variation in the size of muscle fibers
(2) necrotic muscle fibers
(3) chronic inflammatory cell infiltrates
Differential diagnosis:
(1) herditary myopathies
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