Mechanism of neurodegeneration mediated by clonal inflammatory microglia.

Langerhans cell Histiocytosis (LCH) and Erdheim-Chester disease (ECD) are clonal myeloid disorders, associated with MAP-Kinase activating mutations and an increased risk of neurodegeneration. Surprisingly, we found pervasive PU.1+ microglia mutant clones across the brain of LCH and ECD patients with and without neurological symptoms, associated with microgliosis, reactive astrocytosis, and neuronal loss. The disease predominated in the grey nuclei of the rhombencephalon, a topography attributable to a local proliferative advantage of mutant microglia. Presence of clinical symptoms was associated with a longer evolution of the disease and a larger size of PU.1+ clones (p= 0.0003). Genetic lineage tracing of PU.1+ clones suggest a resident macrophage lineage or a bone marrow precursor origin depending on patients. Finally, a CSF1R-inhibitor depleted mutant microglia and limited neuronal loss in mice suggesting an alternative to MAPK inhibitors. These studies characterize a progressive neurodegenerative disease, caused by clonal proliferation of inflammatory microglia (CPIM), with a decade(s)-long preclinical stage of incipient disease that represent a therapeutic window for prevention of neuronal death.

Risk of flare in patients with SLE in remission after hydroxychloroquine or chloroquine withdrawal.

OBJECTIVE: Previous studies have provided evidence that the discontinuation of hydroxychloroquine (HCQ), and chloroquine (CQ), in patients with systemic lupus erythematosus (SLE) is associated with an increased risk of disease flares, with limited information on the level of disease activity at the time of HCQ/CQ discontinuation. Here we aimed to describe the risk of SLE flare after withdrawal of HCQ or CQ in patients with SLE in remission. METHODS: Case-control study (1:2) comparing the evolution of patients with SLE after HCQ/CQ withdrawal for antimalarial retinopathy (cases) with patients with SLE matched for sex, antimalarial treatment duration and age at SLE diagnosis, whose antimalarial treatment was continued throughout the entire follow-up period (controls). To be included in the study, patients had to be in remission for at least one year according to the DORIS classification. The primary endpoint was the proportion of patient experiencing a flare according to the SELENA-SLEDAI Flare Index after a 36-month follow-up. RESULTS: We studied 48 cases and 96 controls. The proportion of patients experiencing a flare was significantly higher in the HCQ/CQ withdrawal group as compared to the maintenance group (15 [31.3%] patients versus 12 [12.5%]; OR 3.1 [95%CI 1.2-8.2], P=0.01). Withdrawal of HCQ/CQ was inferior with respect to occurrence of severe SLE flare (12 [25.0%] vs 11 [11.5%]; OR 2.5 [95%CI 0.9-6.9], P=0.053) and time to first flare (HR 6.3 [2.0-19.9], P<0.005). Elevated serum levels of anti-dsDNA antibodies were identified as a risk factor for SLE flare following HCQ/CQ discontinuation (HR 5.4 [1.5-18.7], P<0.01). CONCLUSION: Withdrawal of HCQ or CQ in patients with SLE in remission is associated with a 3-fold increased risk of relapse.

Identification of new risk factors for hydroxychloroquine and chloroquine retinopathy in systemic lupus erythematosus patients.

BACKGROUND: Long-term hydroxychloroquine (HCQ) or chloroquine (CQ) intake causes retinal toxicity in 0.3-8 % of patients with rheumatic diseases. Numerous risk factors have been described, eg, daily dose by weight, treatment duration, chronic kidney disease, concurrent tamoxifen therapy and pre-existing retinal or macular disease. However, those factors cannot explain the entire risk of developing antimalarial retinopathy. OBJECTIVE: This study was undertaken to identify new risk factors associated with HCQ or CQ retinopathy (QRNP) in systemic lupus erythematosus (SLE) patients. METHODS: This case-control (1:2) study compared SLE patients with QRNP (cases) to those without (controls). Controls were matched for sex and known QRNP risk factors: HCQ and/or CQ treatment duration (±1 year) and age (±5 year) at SLE diagnosis. RESULTS: Forty-eight cases were compared to 96 SLE controls. Multivariable logistic-regression analysis retained the following as independent determinants significantly associated with QRNP: concomitant selective serotonin-reuptake inhibitor (SSRI) or serotonin- and norepinephrine-reuptake inhibitor (SNRI) intake (OR [95 % confidence interval] 6.6 [1.2 to 40.9]; p < 0.01); antiphospholipid syndrome (OR=8.9 [2.2 to 41.4] p < 0.01); blood hydroxychloroquine/desethylchloroquine concentration ([HCQ]/[DCQ]) ratio <7.2 (OR 8.4 [2.7 to 30.8]; p < 0.01) or skin phototype ≥4 (OR 5.5 [1.4 to 26.5]; p = 0.02), but not daily HCQ dose, blood [HCQ] or body mass index. CONCLUSION: The results of this case-control study identified blood [HCQ]/[DCQ] ratio, concurrent SSRI/SNRI therapy, skin phototype ≥4 and antiphospholipid syndrome as new risk factors for QRNP.