A 50-year-old male patient presented with weakness of B/L lower limbs which was symmetrical (distal weakness>> proximal muscle weakness) for 1 month. On examination, ceain skin and nail changes were noted. Patient also complained of myalgia and ahralgia. Lab findings, Raised creatinine kinase levels Raised ANA antibody titre Muscle biopsy was done from the quadriceps femoris muscle. CD4+ cells were found in the cellular infiltrate. IHC study of which protein is a very sensitive diagnostic test for the above condition: -

This is a case of Dermatomyositis. 1ST image shows Perifascicular myofibers (black arrows) bordering on disrupted perimysial connective tissue is atrophic and basophilic- classical of dermatomyositis 2ND image shows the examination findings: - O/E. Erythematous discoloration of eyelids with periorbital edema (Heliotrope rash) Erythematous rash over the extensor surfaces of joints, knuckles (Gottron sign), sun exposed areas of the anterior neck and the chest (Shawl sign) Nail bed telangiectasias Dermatomyositis Idiopathic inflammatory myopathy Presents with: - Proximal and symmetrical weakness Characteristic cutaneous changes Elevated creatine kinase levels Muscle biopsy shows perifascicular atrophy IHC for Myxovirus resistance protein A (MxA) is diagnostic