Selective therapeutic extraction of plasma constituents, revisited

Successful serial plasmapheresis for solar urticaria, a case report and literature review

BACKGROUND/PURPOSE

Amidst the emergence of new therapeutic options, traditional therapeutic plasmapheresis (TPE) used in diseases involving a toxic substance in the plasma, remains a viable alternative for cases of recalcitrant solar urticaria (SU). We emphasize the importance of documenting successful experience with repeated plasmapheresis to increase awareness amongst physicians and dermatologists regarding this effective treatment option.

MATERIAL AND METHOD

We reported a case of recalcitrant SU that had not responded to a combination of H1-antihistamines, immunosuppressants, omalizumab and intravenous immunoglobulin. We introduced serial TPE, which involved two consecutive days of procedures for each course was introduced. We detailed the regimen and highlighted the clinical and objective benefits observed with multiple treatments. Additionally, we compared this to other plasmapheresis regimens and their treatment responses previously reported for solar urticaria.

RESULTS

Our patient underwent serial TPE, totaling 42 procedures over five years. Following the last TPE session, phototesting showed a sustained prolongation of minimal urticating doses (MUDS), which exceeded the maximum tested doses across nearly all ultraviolet (UV) and visible light ranges, with the exception of the two short ultraviolet B (UVB) wavelengths. MUDs increased to 25 from 6 mj/cm2 at 307.5± 5nm, and to 500 from 15 mj/cm2 at 320 ± 10nm, before the initial TPE. In our review, we included five articles covering eight SU patients who received TPE. Of these, the five patients with positive intradermal tests responded particularly well immediately after treatment. However, the condition relapsed within two weeks in one patient and within two months in another. In contrast, the other three patients with negative intradermal tests, showed no significant benefits from the treatment. No serious side effects from TPE were reported amongst the patients.

CONCLUSIONS

This review underscores the efficacy of serial plasmapheresis procedures in treating refractory cases of SU, high3lighting the robust results observed.

Glycine receptor autoantibody binding to the extracellular domain is independent from receptor glycosylation

Glycine receptor (GlyR) autoantibodies are associated with stiff-person syndrome and the life-threatening progressive encephalomyelitis with rigidity and myoclonus in children and adults. Patient histories show variability in symptoms and responses to therapeutic treatments. A better understanding of the autoantibody pathology is required to develop improved therapeutic strategies. So far, the underlying molecular pathomechanisms include enhanced receptor internalization and direct receptor blocking altering GlyR function. A common epitope of autoantibodies against the GlyRα1 has been previously defined to residues ¹A-³³G at the N-terminus of the mature GlyR extracellular domain. However, if other autoantibody binding sites exist or additional GlyR residues are involved in autoantibody binding is yet unknown. The present study investigates the importance of receptor glycosylation for binding of anti-GlyR autoantibodies. The glycine receptor α1 harbors only one glycosylation site at the amino acid residue asparagine 38 localized in close vicinity to the identified common autoantibody epitope. First, non-glycosylated GlyRs were characterized using protein biochemical approaches as well as electrophysiological recordings and molecular modeling. Molecular modeling of non-glycosylated GlyRα1 did not show major structural alterations. Moreover, non-glycosylation of the GlyRα1^N38Q did not prevent the receptor from surface expression. At the functional level, the non-glycosylated GlyR demonstrated reduced glycine potency, but patient GlyR autoantibodies still bound to the surface-expressed non-glycosylated receptor protein in living cells. Efficient adsorption of GlyR autoantibodies from patient samples was possible by binding to native glycosylated and non-glycosylated GlyRα1 expressed in living not fixed transfected HEK293 cells. Binding of patient-derived GlyR autoantibodies to the non-glycosylated GlyRα1 offered the possibility to use purified non-glycosylated GlyR extracellular domain constructs coated on ELISA plates and use them as a fast screening readout for the presence of GlyR autoantibodies in patient serum samples. Following successful adsorption of patient autoantibodies by GlyR ECDs, binding to primary motoneurons and transfected cells was absent. Our results indicate that the glycine receptor autoantibody binding is independent of the receptor's glycosylation state. Purified non-glycosylated receptor domains harbouring the autoantibody epitope thus provide, an additional reliable experimental tool besides binding to native receptors in cell-based assays for detection of autoantibody presence in patient sera.

Optic neuritis with potential for poor outcome

The Optic Neuritis Treatment Trial previously reported that corticosteroids accelerated visual recovery in optic neuritis (ON) without improving outcome. This finding related largely to multiple sclerosis (MS), and subsequently neurologists tended to await spontaneous recovery in ON. Since then, non-MS cases of ON have been identified with antibodies to aquaporin-4 (AQP4) or myelin oligodendrocyte glycoprotein (MOG). These disorders can closely mimic multiple sclerosis-associated or idiopathic demyelinating optic neuritis (MS/IDON) initially but risk a worse visual outcome. Scrutinising the clinical features and neuroimaging often enables differentiation between MS/IDON and other causes of ON. Early treatment with high-dose corticosteroids is an important determinant of visual outcome in non-MS/IDON. Prompt use of plasma exchange may also save sight. In this review, we contrast the presentations of myelin oligodendrocyte glycoprotein associated optic neuritis (MOG-ON) and aquaporin 4 associated optic neuritis (AQP4-ON) with MS/IDON and provide an approach to acute management while awaiting results of antibody testing.

The mechanisms of action of plasma exchange

The initial description of therapeutic plasma exchange (TPE) in an animal model was published almost 100 years ago. Since that time, this treatment has been applied to a wide variety of diseases but limited research has been published examining the mechanisms of action of TPE. The therapeutic effects of TPE could include the removal of pathological substances from the blood, such as monoclonal paraproteins and autoantibodies, as well as the replacement of deficient plasma components when plasma is used as a replacement fluid. Beyond these potential mechanisms, other possible mechanisms include possible alterations in lymphocyte proliferation and function that could sensitize these cells to immunosuppressant and chemotherapeutic agents and alterations in the immune system including changes in B and T cell numbers and activation, increased T suppressor function, and alteration in T-helper cell type 1/2 (Th1/Th2) ratio. Much remains unknown about the mechanisms of action of TPE, indicating a need for basic research into this therapy.