Background/Purpose: Neopterin is a metabolic product of guanosine triphosphate, which is produced by macrophages upon stimulation with interferon-gamma from activated T helper cells. Despite the initial studies showing elevated neopterin in children with active Juvenile Dermatomyositis, the broad adoption of neopterin as biomarkers in clinical practice is still limited. We aim to study the immunological and clinical differences between newly diagnosed JDM patients with elevated and normal serum neopterin levels.

Methods: Children with JDM who had serum neopterin before initiating medical therapy were included. Elevated serum neopterin was defined by levels > 10 nmol/l. We assessed T, B, and NK cell populations, Myositis-specific antibodies, Muscle enzymes and Disease Activity Score for skin (sDAS), muscle (mDAS), Total (tDAS). Student’s t-test and chi-square to compare the baseline characteristics, disease activity markers, and among the two groups.

Results: 113 subjects (77% female, 77% white, 3.5 % black, 14.2 % Hispanic) were included in this study. 80% of untreated JDM patients had elevated serum neopterin. The mean age of onset was similar in the two groups however the duration of untreated disease was significantly shorter in the patients with elevated neopterin (7.7 months vs 14.1 months p = 0.007). Among the different MSAs group, anti-MJ group has the highest the mean neopterin at 26.7+/- 4.4 nmol/l and the Mi2 group has the lowest level at 14.2 +/- 6.0 nmol/l however the difference was not statistically significant . Also, the group with elevated neopterin had significantly more active disease with mean tDAS 11.7 vs 9.0 (p=0.0009), mDAS 5.7 vs 3.7 (p=0.005), sDAS 6.0 vs 5.4 (p =0.04), CK level 475.9 vs 274.1 IU/L (p= 0.006), Aldolase 21.0 vs 7.8 U/L (p=0.05) and ESR 19 vs 10.7 mm/hr (p=0.01). The flow cytometry showed reduced T cells (1517 vs 2348 /mm3 p < 0.001) and NK cells (144 vs 248 /mm3 p =0.002). TNFalpha-308AA/AG polymorphism was more common in subject with elevated neopterin than TNFalpha-308GG (chi-square p = 0.05). Of note, there was a positive correlation between the levels of serum neopterin and tDAS (R² = 0.14, p = < 0.001) and mDAS (R² = 0.17, p = < 0.001) but not sDAS.

Conclusion: Elevated serum neopterin is seen in 80 % of untreated JDM. JDM Patients with elevated have more muscle weakness and elevated muscle enzymes. Also, elevated neopterin is associated with an increased frequency of TNFalpha-308AA/AG polymorphism and decreased absolute NK, and T cells count.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/immunological-and-clinical-features-of-untreated-juvenile-dermatomyositis-patients-with-elevated-neopterin/