Lim et al. Lymphopenia in treatment-naive relapsing multiple sclerosis. Neurol Neuroimmunol Neuroinflamm. 2016 Aug 12;3(5):e275. doi: 10.1212/NXI.0000000000000275. eCollection 2016.
Background: Lymphopenia accompanies some autoimmune diseases. Several studies, but not others, have suggested that lymphopenia occurs in treatment-naive multiple sclerosis (MS), so the issue remains unresolved.
Methods: Data were collected retrospectively during an institutionally approved service evaluation of blood test monitoring of patients with relapsing MS in a regional MS service in Southampton, UK, over a 2-year period (2012–2014). Control lymphocyte data were derived from preoperative blood counts of age- and sex-matched individuals undergoing septoplasty in the same hospital for structural reasons, excluding neoplastic and infective operative indications.
Results: Seven hundred sixty-four patients were identified with blood test data (table). Baseline and post-treatment blood tests were available in 466 and 247 patients, respectively. Average blood test frequency was 4 per year. Lymphocyte counts were relatively stable with time, with a coefficient of variation of 7.5%. The mean lymphocyte count in treatment-naive patients with MS was 2.18 × 109/L with an SD of 0.66 × 109. Lymphopenia was present in 10% (48 patients; 46 grade I, one grade II, one grade III). In only 3 cases steroids were administered in the month before lymphopenia. There was no association between pretreatment lymphocyte count and any patient characteristic or month or season.
Discussion: Since the lymphocyte reference range covers 95% of values in a healthy population, lymphopenia is expected in 2.5%. In our treatment-naive relapsing MS population, we found lymphopenia in 10%. Moreover, lymphopenia was not associated with relapsing activity. Hence, the lymphopenia in patients with MS is unlikely to be related to autoimmunity. A more likely explanation is stress-induced lymphopenia in both cohorts, through cortisol or Epstein-Barr activation.