Purpose: To report a case of dermatomyositis (DM) with secondary Sjögren's syndrome (SS) and propose the clinical application of technetium-99m pyrophosphate ((99m)Tc-PYP) scan.
Case report: A 50-year-old woman had progressive proximal muscle weakness of bilateral thighs, myalgia, tea-colored urine, and exercise intolerance for 6 months. Physical examination showed malar rash, V-sign, periungual erythema, and mechanic hands. Neurological assessment showed symmetric pelvic-girdle weakness, myopathic face, waddling gait, but preserved deep tendon reflex and sensory functions. DM was diagnosed on the basis of typical rashes and serum creatinine kinase elevation (7397 IU/L). Aside from myopathic symptoms, dry eye and mouth were reported. Thorough autoantibody searches showed positive anti-SSA/Ro antibody (198 U/ml). Both Schirmer's test and sialoscintigraphy were positive, leading secondary SS as diagnosis. Initial (99m)Tc-PYP scan revealed increased radiouptake in the muscles of bilateral thighs, compatible with clinical assessment. Followup scan three months later shows abnormal but attenuated radiouptake at bilateral thighs, in the presence of nearly-complete clinical recovery.
Conclusion: DM with secondary SS in adult is a unique disease entity, with predominantly myopathic symptoms and satisfactory therapeutic response as its characteristics. Our serial muscle imaging studies suggest that (99m)Tc-PYP scan is at once anatomically-specific and persistently-sensitive to microstructural damages within inflammatory muscles, enabling clinician to monitor disease activity and therapeutic response.