INFLAMMATORY MYOPATHIES: P.162IgG-4 related myositis - a new entity among inflammatory myopathies

Abstract

IgG4-related diseases (IgG4RD) are exceedingly rare, have only been recently discovered and the nosological spectrum is only beginning to be understood. Affected patients suffer from subacute non-specific general complaints often associated with organ-specific affection typically of the salivary or lacrimal glands, formation of so-called pseudo-tumours with fibrous characteristics, and interestingly often multi-organ affections. Gold standard for diagnosis of IgG4RD is the histopathological analysis, highlighting the characteristic lymphocytoplasmic infiltrates, storiform fibrosis and obliterative phlebitis in combination with IgG4-positive Plasma cells. We present a 55-year-old female patient with a 30-year history of atypical rheumatoid arthritis suffering from a 12-year history of axial muscle weakness including paravertebral muscles. No other organs were involved. Her laboratory markers included eosinophilia, elevated soluble IL-2 receptor and IgG4. On muscle biopsy an unusually dense lymphomonocytic infiltrate including numerous Eosinophils and Giant cells as well as numerous IgG4-positive plasma cells were detectable. In general, IgG4-RD responds well to treatment, especially to B cell depletion, however our patient did not. As a second-line treatment, she received a JAK1 and JAK2 inhibitor, which dramatically improved her muscle strength over a 3 months period. This report highlights that myositis can be the sole presentation of IgG4 related disease and that treatment may require alternative approaches, which in turn open speculations about pathophysiological underpinnings of the disease.