FROM DERMATOMYOSITIS SINE DERMATITIS TO A COMPLETE FORM OF JUVENILE DERMATOMYOSITIS: AN INTRIGUING CASE REPORT!

Although rare, juveniledermatomyositis (JD) is the mostcommoninflammatorymyopathy in children. It is a vasculopathycategorizedintoclassical and non-classicalsubtypes, the latter includingamyopathicdermatomyositis (DM) and dermatomyositis (DM) withoutdermatitis. DM sine dermatitisis a rarelydescribedphenotype, representing an atypicalformwith no classiccutaneous manifestations, complicatingdiagnosis, and isthereforeidentified on the basis of well-defined diagnostic criteria.In this article, we report the case of a twelve-year-oldchildpresentingwith muscle weakness and myalgias one monthprior to admission. Clinicalexaminationrevealed a progressive myogenic syndrome withdysphagia to solids, with no other multi-visceralinvolvement or signs of severity. Mucocutaneousexaminationwaspoor, revealingonlyleukokeratosis of the leftlateralborder of the tongue, with no otherassociated skin signs. Muscle enzymes wereelevated. A myositis-specificautoantibodyassayrevealed a positive anti-NXP2. Electromyographyshowed a diffuse emyogenic syndrome. MRI of the lowerlimbsshowed diffuse hypersignal in the muscle tissue. A diagnosis of dermatomyositis sine dermatitiswas made, and treatmentwasinitiatedwith oral prednisone 2 mg/kg/day, combinedwithsubcutaneous Methotrexate 25 mg/week. In the absenceimprovementafter 5 months of treatment, weswitched to mycophenolatemofetil (MMF) at a dose of 600 mg/m² twicedaily, with good progression.Afterlosinghissight and stoppingtreatment for a long time, the patient returnedaftertwoyearswith a full clinicalpicture of juveniledermatomyositis, withsevere muscle weakness and skin signs. This time, given the severity of the disease, ourtherapeuticapproachwas to switch to third-line treatmentwithinfliximab 5 mg/kg biotherapyadministered at specificintervals, with good improvement.