[17, 18].
Moreover, most cases of reversible lesions demonstrate the evidence that
cytotoxic edema of the SCC is an important mechanism in this syndrome[28]. Miyata R et al [16], reported that
patients with MERS has an elevated IL-6 and IL-10 levels in CSF.
Cytotoxic edema in the neurons, astrocytes, and oligodendrocytes of the
SCC, caused by cytokines, may offer the best explanation. Recently,
these lesions have been called cytotoxic lesions of the corpus callosum
or CLOCC lesions [28, 29]. This could explain the elevated
white cells in the CSF as it is the case of our patient. A recent review
study [19] found that more than half (15/23) cases had
elevated white cells in the CSF. Even if we take all these hypotheses
into account, MERS still be a rare syndrome with unclear pathogenesis
and none of the existing hypotheses may explain why MERS specially
involves the site splenium.
In addition, serum sodium levels were significantly lower in patients
with MERS than in age matched controls. These data support the
hypothesis that a transient cerebral edema may develop as a result of
hyponatremia [17].
RTX is a murine/human‐chimeric monoclonal antibody that depletes CD20+ B
cells through both cell‐mediated and complement mediated cytotoxic
effects [30]. It is widely used in malignancy and
immune‐mediated diseases in combination with corticosteroids and other
immunosuppressive drugs.
RTX is also effective for both induction therapy and treatment of
relapses in IgG4-RD specially in nephrologic flare refractory to
corticosteroids [31]. Its administration rarely causes
serious neurologic adverse events. However, it was reported to lead to
complement activation, cell lysis and subsequent massive release of
cytokines, culminating in cytokine release syndrome and systemic
inflammatory response syndrome [32-35]. This could, in
part, explain the early development of MERS after rituximab in our
patient. But MERS induced by Rituximab has never been reported before.
However, Posterior reversible encephalopathy syndrome (PRES), which may
be a differential diagnoses for MERS, has been reported to be related to
RTX [3].
PRES is a rare clinical disorder which has nearly clinical symptoms to
MERS. It manifests also with headache, convulsions, altered level of
consciousness and reversible cerebral edema. It is also a reversible
disorder that requires rapid diagnosis by demonstrating the presence of
characteristic vasogenic edema on brain MRI in the appropriate clinical
context [36, 37].
Progressive multifocal leukoencephalopathy (LEMP) after RTX, which is a
rare opportunistic infection due to reactivation of JC virus into the
central nervous system, is described [38].
Acute disseminated encephalomyelitis (ADEM) is being the main
differential radiologic diagnosis of MERS [39] but RTX is
effective for this disease [40].
The neurological manifestations presented by the patient cannot also be
related to his underlying disease. IgG4-related disease can involve
nearly any organ system, including the central and peripheral nervous
systems but MERS has never been reported [41].
Furthermore, MERS is a rare disease and evidence on the therapeutic
approaches is currently not yet available. Methylprednisolone pulse
therapy and IVIG were prescribed in MERS patients without any evidence
of efficacy of these treatments. However, many patients without
methylprednisolone pulse therapy or IVIG recovered clinically
completely, which suggests that those treatments may not be necessary[42]. Our patient was treated by methylprednisolone pulse
therapy and IVIG as we had a severe neurological involvement and we were
face an auto immune disease (IgG4-RD).