New treatment offers hope for children with debilitating skin and muscle disease

JDM is a rare chronic autoimmune disease of children characterised by inflammation of the muscles, skin and other organs. , In the UK, the reported incidence of JDM is two to three cases per million children younger than 16 years old, with a median age at onset of 6.8 years; JDM is more common in girls than boys, by a ratio of approximately 2.3:1. Characteristic findings include skin rash, skin ulceration, and muscle weakness.

In general, children with JDM are able to lead normal lives; however, some patients with JDM have a disease course that is refractory to multiple drug treatments. For those children where treatments have failed, prolonged disease activity has been shown to be associated with increased mortality and complications, such as scarring, pain due to trapped nerves, and shortening of the muscles causing joints to stay bent.

"High levels of the cell signalling protein TNF have been reported in JDM patients with a long disease course, suggesting this immune cell regulator may play a significant role in refractory disease," said Dr Raquel Campanilho-Marques of the Institute of Child Health, University College London, UK. "There are no published clinical trials (only case reports) of this therapy, but some are in progress. Our study is one of the largest to explore the efficacy and safety of anti-TNF therapy in a large independent cohort of JDM patients."

Evaluation of 66 patients with JDM, recruited from the UK JDM Cohort and Biomarker Study and actively treated with anti-TNF agents, showed significant improvements in muscle and skin involvement, as well as in overall disease activity. There were significant changes in the median values of two standard muscle measurements: the Childhood Myositis Assessment Scale and Manual Muscle Testing (p<0.0001 and p=0.0097 respectively). There were also significant improvements in skin involvement assessed using the modified skin Disease Activity Score (p<0.0001). Global disease activity also improved significantly (p<0.0001).

Around one quarter of the patients in this study switched their anti-TNF treatment, with just under two-thirds of these switches due to therapy failure, one quarter due to adverse events and one eighth due to patient preference for subcutaneous administration. Of 21 adverse reactions registered, seven were considered severe (anaphylactic reactions on infliximab infusion). Three quarters of the mild to moderate adverse reactions were due to infection; in four of which, the patient was switched to another TNF antagonist, while in the remaining patients, temporarily withholding the drug proved sufficient. No cases of TB were registered.