MDA5-Related Juvenile Dermatomyositis and ILD: Case Series and Literature Review

Overview

This report presents three pediatric cases of anti-MDA5-positive juvenile dermatomyositis (JDM) complicated by interstitial lung disease (ILD) in South African children. It highlights the clinical course from rapid progression to a quiescent state and reviews treatment strategies for rapidly progressive ILD (RP-ILD) associated with anti-MDA5 JDM.

Background

Juvenile dermatomyositis is a rare autoimmune condition in children characterized by muscle weakness and skin manifestations. Patients with anti-MDA5 autoantibodies exhibit a distinct phenotype including arthritis, ulcerative skin lesions, and a heightened risk of ILD, particularly RP-ILD. The prevalence and severity of ILD in anti-MDA5 JDM vary geographically, with higher rates reported in East Asia compared to Europe and North America. Data on African populations remain scarce, underscoring the importance of documenting cases from this region.

Data Highlights

Case 1 (11-year-old boy) presented with muscle weakness (CMAS 26/52), arthritis, and characteristic skin lesions. Initial pulmonary function tests showed restrictive and obstructive patterns (FVC 41% predicted, PEF 67%, MEF50 54%). Despite immunosuppressive therapy including corticosteroids, methotrexate, mycophenolate mofetil, IVIG, cyclophosphamide, rituximab, plasma exchange, and tofacitinib, the patient experienced rapid respiratory decline with pneumomediastinum and extensive ILD confirmed by HRCT. Following therapeutic escalation, clinical improvement was observed with normalization of ferritin and reduction in oxygen requirements.

Key Findings

• Anti-MDA5-positive JDM patients often present with arthritis, ulcerative skin lesions, and mild muscle involvement but are at risk for ILD and RP-ILD.
• Geographic variation exists in anti-MDA5 prevalence and ILD progression, with East Asian cohorts showing higher rates of RP-ILD compared to European and North American cohorts.
• This is the first documented case series of African children with anti-MDA5 JDM and ILD, expanding understanding of disease presentation in this population.
• Rapid progression of ILD can occur despite standard immunosuppressive therapies, necessitating early aggressive treatment including cyclophosphamide, rituximab, plasma exchange, and JAK inhibitors like tofacitinib.
• Clinical improvement and transition to a quiescent state are possible with timely therapeutic escalation, as evidenced by normalization of inflammatory markers and improved pulmonary function.

Clinical Implications

Clinicians should maintain a high index of suspicion for ILD in anti-MDA5-positive JDM patients, especially when respiratory symptoms or pulmonary function abnormalities develop. Early and aggressive immunosuppressive therapy, including biologics and plasma exchange, may be required to manage rapidly progressive ILD and improve outcomes. Monitoring inflammatory markers such as ferritin and pulmonary imaging is critical to guide treatment adjustments.

Conclusion

Anti-MDA5-associated JDM in African children can present with severe ILD that may rapidly progress but can respond to intensive immunomodulatory treatment. These cases underscore the need for awareness and prompt intervention to improve prognosis in this rare but serious complication.

References

1. Fujimoto et al. 2016 -- Clinical features of anti-MDA5 antibody-positive dermatomyositis
2. Sato et al. 2013 -- Prevalence and clinical characteristics of anti-MDA5 in East Asian JDM
3. Smith et al. 2018 -- UK cohort study on anti-MDA5 JDM prevalence and ILD outcomes
4. Johnson et al. 2020 -- North American cohort of anti-MDA5-positive JDM and ILD
5. PRINTO recommendations 2010 -- Treatment guidelines for juvenile dermatomyositis
6. Aggarwal et al. 2017 -- Rituximab use in refractory anti-MDA5 dermatomyositis