Increased kappa free light chain index in patients with late onset multiple sclerosis.

INTRODUCTION

Intrathecal immunoglobulin-G synthesis is a pathological hallmark of multiple sclerosis (MS). Cerebrospinal fluid (CSF) kappa-free light chain (κFLC) detection has emerged as a new biomarker in MS, but little is known about its expression and variance across distinct patient subgroups.

OBJECTIVE

To assess and compare intrathecal synthesis through kFLC index between patients with early and late onset MS.

METHODS

An exploratory retrospective single-center cohort study including consecutively diagnosed MS patients was conducted. Nephelometric kFLC measurements of paired serum/CSF samples collected at MS diagnosis were obtained. A cut-off for increased κFLC index was established at ≥6.1 as per previous published reports. Two groups were defined: early onset (EO) patients (first MS symptoms < 50 years) and late onset (LO) patients (first MS symptoms ≥ 50 years).

RESULTS

Sixty (60) patients were included, 42(70 %) female, with a mean age of 48.3 years (±14.3; min18-max79) and a mean disease duration of 5.2 years (± 4.8; min 0.5-máx 23). 25 (41.7 %) LO patients were included. Groups did not differ in demographic or clinical variables. Although the prevalence of CSF-restricted OCB was similar between groups (EO n = 31, 88.6 %; LO n = 22, 88,0 %, p = 1.000), the prevalence of a kFLC index >6.1 was significantly higher in LO MS patients (n = 22, 88.0 % vs EO n = 22, 62,9 % p = 0.040).

CONCLUSION

In this cohort, a higher prevalence of increased kFLC index was found among patients with late-onset MS. This may reflect a longer period of intrathecal dysimune reactions connected to MS pathological onset, even if not clinically expressed until later stages.