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Objectives: This study aimed to determine the association between the dosage and pharmacokinetics of mycophenolate mofetil (MMF) in juvenile patients with autoimmune diseases. Methods: Totally, 29 patients were administered oral MMF. The blood concentrations of mycophenolate acid (MPA) at seven points, the area under the time-concentration curve (MPA-AUC0-12h), the peak concentration (Cmax), and the time to peak concentration (Tmax) were measured. To obtain a dose-normalized MPA-AUC0-12h value, the actual measured MPA-AUC0-12h value was divided by the dose value of the morning administration corrected for body weight (BW) or body surface area (BSA). The patients were classified into three age groups (group 1, -10 years; group 2, >10-15 years; and group 3, >15 years), and pharmacokinetic parameters were compared among the groups. Results: In total, we obtained 37 measurements. The actual measured MPA-AUC0-12h values and the MPA-AUC0-12h values corrected for dose per BW and Tmax were lower in young patients. The MPA-AUC0-12h values corrected for dose per BSA and Cmax were comparable among all the groups. Conclusion: In patients with juvenile autoimmune diseases, determining MMF administration dosage according to BSA may facilitate MPA-AUC0-12h value prediction. [ABSTRACT FROM AUTHOR]

Objectives: This study investigated the association between myositis-specific autoantibodies (MSAs) and clinical subsets of juvenile dermatomyositis (JDM) in Japanese patients. Methods: Twenty-one patients at a single center who developed initial or relapsed JDM from 2011 to 2016 were analyzed. Serum concentrations of MSAs against TIF1-c, MDA5, NXP2, Mi-2, ARS, and SAE were measured by enzyme-linked immunosorbent assays. Clinical symptoms and laboratory data were obtained from clinical records. Clinical characteristics were compared in patients with autoantibodies against TIF1-c, MDA5, and NXP2. Results: Of the 21 patients, 20 (95.2%) were positive for one or more MSAs, including nine (42.9%), five (23.8%), six (28.6%), and one (4.8%) positive for anti-TIF1-c, anti-MDA5, anti-NXP2, and anti-Mi-2 autoantibodies. No patient was positive for anti-ARS or anti-SAE autoantibodies. The frequency of diffuse cutaneous lesions was higher in patients with anti-TIF1-c autoantibodies. Anti-MDA5 autoantibody-positive patients had features of interstitial lung disease on chest computed tomography. Severe muscle damage at disease onset was significantly associated with positivity for anti-NXP2 autoantibodies. Conclusion: Similar to findings in Western countries, the clinical characteristics of JDM in Japanese may differ for each type of MSAs. [ABSTRACT FROM AUTHOR]

Juvenile dermatomyositis is the most common type of juvenile idiopathic inflammatory myopathy mainly affecting the skin and proximal muscles. We have published the Japanese version of 'Clinical practice guidance for juvenile dermatomyositis (JDM) 2018 'consisting of a review of articles in the field and evidence-informed consensus-based experts' opinion on the treatment strategy in collaboration with The Pediatric Rheumatology Association of Japan and The Japan College of Rheumatology under the financial support by 'Research on rare and intractable diseases, Health and Labor Sciences Research Grants'. This article is a digest version of the Japanese guidance. [ABSTRACT FROM AUTHOR]

Objectives: The objective of this study is to identify risk factors for hypersensitivity reaction (HSR) to tocilizumab (TCZ) in systemic juvenile idiopathic arthritis (sJIA). Methods: Clinical records of 40 patients with sJIA administered TCZ at one center were retrospectively reviewed. Patients were divided into HSR or non-HSR groups depending on the presence of HSR between the first and third TCZ administrations; clinical and laboratory assessments, including serum cytokine profile, were compared. Results: Five patients displayed HSR following the third TCZ administration. They were significantly younger, shorter, and lighter, with a higher peak body temperature than non-HSR patients following the third administration. Their serum C-reactive protein (CRP) level was undetectable following the first administration but detectable by the third administration. Before the third administration, the white blood cell counts and serum levels of CRP and sTNFRII were significantly higher in the HSR group than in the non-HSR group. The serum levels of interleukin-18 and -6 before the third TCZ administration were higher and lower than those before the first administration in the HSR and non-HSR groups, respectively. Conclusion: Patients with sJIA having a younger age, shorter stature, and lighter weight and those showing increased disease activity in the early period of TCZ administration may be at higher risk of TCZ-induced HSR. [ABSTRACT FROM AUTHOR]