Victoria Tüngler

Spinal muscular atrophy (SMA) is the leading genetic cause of infant mortality, characterized by progressive neuromuscular degeneration resulting from mutations in the survival motor neuron (SMN1) gene. The availability of disease-modifying therapies for SMA therapies highlights the pressing need for easily accessible and cost-effective blood biomarkers to monitor treatment response and for better disease management. Additionally, the wide implementation of newborn genetic screening programs in Western countries enables presymptomatic diagnosis of SMA and immediate treatment administration. However, the absence of monitoring and prognostic blood biomarkers for neurodegeneration in SMA hinders effective disease management. Neurofilament light protein (NfL) is a promising biomarker of neuroaxonal damage in SMA and reflects disease progression in children with SMA undergoing treatment. Recently, the European Medicines Agency issued a letter of support endorsing the potential utilization of NfL as a biomarker of pediatric neurological diseases, including SMA. Within this review, we comprehensively assess the potential applications of NfL as a monitoring biomarker for disease severity and treatment response in pediatric-onset SMA. We provide reference ranges for normal levels of serum based NfL in neurologically healthy children aged 0–18 years. These reference ranges enable accurate interpretation of NfL levels in children and can accelerate the implementation of NfL into clinical practice.

Background and Objective The spectrum of myelin oligodendrocyte glycoprotein (MOG) antibody–associated disorder (MOGAD) comprises monophasic diseases such as acute disseminated encephalomyelitis (ADEM), optic neuritis (ON), and transverse myelitis and relapsing courses of these presentations. Persistently high MOG antibodies (MOG immunoglobulin G [IgG]) are found in patients with a relapsing disease course. Prognostic factors to determine the clinical course of children with a first MOGAD are still lacking. The objective of the study is to assess the clinical and laboratory prognostic parameters for a risk of relapse and the temporal dynamics of MOG‐IgG titers in children with MOGAD in correlation with clinical presentation and disease course. Methods In this prospective multicenter hospital-based study, children with a first demyelinating attack and complete data set comprising clinical and radiologic findings, MOG-IgG titer at onset, and clinical and serologic follow-up data were included. Serum samples were analyzed by live cell-based assay, and a titer level of ≥1:160 was classified as MOG-IgG–positive. Results One hundred sixteen children (f:m = 57:59) with MOGAD were included and initially diagnosed with ADEM (n = 59), unilateral ON (n = 12), bilateral ON (n = 16), myelitis (n = 6), neuromyelitis optica spectrum disorder (n = 8) or encephalitis (n = 6). The median follow-up time was 3 years in monophasic and 5 years in relapsing patients. There was no significant association between disease course and MOG-IgG titers at onset, sex, age at presentation, or clinical phenotype. Seroconversion to MOG-IgG–negative within 2 years of the initial event showed a significant risk reduction for a relapsing disease course. Forty-two/one hundred sixteen patients (monophasic n = 26, relapsing n = 16) had serial MOG-IgG testing in years 1 and 2 after the initial event. In contrast to relapsing patients, monophasic patients showed a significant decrease of MOG-IgG titers during the first and second years, often with seroconversion to negative titers. During the follow-up, MOG-IgG titers were persistently higher in relapsing than in monophasic patients. Decrease in MOG-IgG of ≥3 dilution steps after the first and second years was shown to be associated with a decreased risk of relapses. In our cohort, no patient experienced a relapse after seroconversion to MOG-IgG–negative. Discussion In this study, patients with declining MOG-IgG titers, particularly those with seroconversion to MOG-IgG–negative, are shown to have a significantly reduced relapse risk.

Objective: The aim of this study was to evaluate neurofilament light chain as blood biomarker for disease activity in children and adolescents with different types of spinal muscular atrophy (SMA) and establish pediatric reference values.Methods: We measured neurofilament light chain levels in serum (sNfL) and cerebral spinal fluid (cNfL) of 18 children with SMA and varying numbers of SMN2 copies receiving nusinersen by single‐molecule array (SiMoA) assay and analyzed correlations with baseline characteristics and motor development. Additionally, we examined sNfL in 97 neurologically healthy children.Results: Median sNfL levels in treatment‐naïve SMA patients with 2 SMN2 copies are higher than in those with >2 SMN2 copies (P < 0.001) as well as age‐matched controls (P = 0.010) and decline during treatment. The median sNfL concentration of healthy controls is 4.73 pg/mL with no differences in sex (P = 0.486) but age (P < 0.001). In all children with SMA, sNfL levels correlate strongly with cNfL levels (r = 0.7, P < 0.001). In children with SMA and 2 SMN2 copies, sNfL values correlate with motor function (r = –0.6, P = 0.134), in contrast to older SMA children with >2 SMN2 copies (r = –0.1, P = 0.744).Interpretation: Reference sNfL values of our large pediatric control cohort may be applied for future studies. Strong correlations between sNfL and cNfL together with motor function suggest that sNfL may be a suitable biomarker for disease activity in children with 2 SMN2 copies and those with >2 SMN2 copies within their initial stages during early childhood.

To review recent scientific advances and therapeutic approaches in the expanding field of type I interferonopathies.