CPC05 A case of adult-onset en coup de sabre responsive to abatacept

En coup de sabre (ECDS) is a rare subtype of linear morphoea, located on the forehead or frontoparietal scalp. It is typically seen in children, with < 100 cases of adult-onset ECDS reported. The name derives from the characteristic scar that indents the skin and underlying structures. It can involve the dermis, subcutaneous tissue, muscle, bone and underlying structures, with resulting extracutaneous manifestations including neurological, ocular and oral complications. A 70-year-old female patient presented with a progressive, year-long history of forehead linear atrophy and induration manifesting along a decade-long vertical rhytid. Examination revealed a right paramedian linear atrophic depression with a violaceous rim. This extended posteriorly into her frontal scalp, with associated linear cicatricial alopecia, and inferiorly towards her orbital rim. Histopathology highlighted scarring alongside lymphocytic inflammation and focal subtle vacuolar interface change. Given both the clinical and pathological features, a diagnosis of ECDS was made. Magnetic resonance imaging of her brain revealed no skeletal or parenchymal abnormalities. Ophthalmology examination was normal. Given a history of progression, and the clinical appearance of active disease, immunosuppressive therapy was warranted. Abatacept 125 mg subcutaneously weekly was chosen over methotrexate given the presence of comorbid liver disease. An 8-month course was completed, improving the appearance of the lesion. No further activity has been noted 1 year off treatment. ECDS is a chronic autoimmune fibrosing condition of the skin and underlying tissue with the potential for significant disease-associated morbidity. There is currently no universal diagnostic test for ECDS and no pathological marker that correlates with disease activity. Histology often highlights a perivascular and periappendageal lymphocytic infiltrate, with vacuolar interface changes. All patients should undergo brain imaging to determine the extent of disease. While its aetiopathogenesis remains unknown, there is evidence to suggest that the early inflammatory stages are driven by the T helper (Th)1/Th17 pathway, while the Th2 pathway may be responsible for the fibrosis and damage observed later in the disease. This concept underpins the efficacy seen with abatacept, which inhibits T-lymphocyte activation. Abatacept is a lesser-recognized but important therapeutic option in our armamentarium for managing ECDS. Studies have sho