Idiopathic inflammatory myopathies are a group of rare but serious diseases. The treatment of refractory
idiopathic inflammatory myopathy is always challenging, especially in children. Three cases of refractory
idiopathic inflammatory myopathy treated by
rituximab were reported and discussed with the review of relevant literature. All were female with on-set age of 8 years and 6 months, 11 years and 7 months, 4 years and 2 months old, respectively. All had acute onset, presenting with progressive and severe
muscle weakness. All lost ambulation within 1 or 2 months, with difficult swallowing and low voice. Respiratory distress occurred in case 2 after an attack of
asphyxia due to an aspiration of sputum, and
ventilator support was required for 1 month. Rashes were detected at the initial stage of the disease in cases 2 and 3. Patient 2 showed facial erythematous papules, spreading to her neck and hands. Patient 3 showed purplish eyelids with peri-orbital swelling, generalized
edema involving all her limbs.
Creatine kinase (CK) levels were markedly elevated in all the patients, ranging from 6 000 IU/L to 28 819 IU/L. Anti-SRP antibody was identified in cases 1, and anti-NXP2
antibodies were confirmed in cases 2 and 3. MRI of both thighs in all the patients showed profound muscle and fascial
edema. Muscle pathology of patient 1 showed prominent fiber variation and endomysial
fibrosis, with overexpression of MHC-Ⅰ. While muscle pathology in patients 2 and 3 showed scattered fiber
necrosis, regeneration, endomysial
edema without inflammatory cell infiltration. All the patients were diagnosed with
idiopathic inflammatory myopathy and failed to the initial treatment including adequate
glucocorticoids and high-dose immunoglobulin therapy. Other
immunosuppressants (
methotrexate,
cyclophosphamide) were also tried in cases 2 and 3 with poor response. Then all the patients were treated with
rituximab combined with
glucocorticoids. Patient 1 regained normal strength and discontinued
rituximab at the end of her last follow-up (2 years and 7 mouths). Though
calcinosis developed during the follow-up period, significant improvement was noticed in cases 2 and 3 (both regained the ability to walk independently) at the end of their last follow-up after 2 years and 8 months, 3 years and 2 months respectively. Long-term
rituximab therapy may improve the prognosis of refractory
idiopathic inflammatory myopathy, especially with positive anti-SRP and anti-NXP2
antibodies.