Abstract
Background Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a rare but debilitating disease within the stiff-person syndrome (SPS) spectrum and is characterised by muscle rigidity, spasms, myoclonus, dysautonomia and brainstem dysfunction. The exact pathogenetic mechanism is unclear, although there is an association with the presence of glycine receptor antibodies in serum and cerebrospinal fluid, and some cases are paraneoplastic.
Results Here we report a complex case of paraneoplastic PERM associated with an otherwise subclinical monoclonal B-cell lymphocytosis (MBL) of the non-chronic lymphocytic leukaemia (CLL) phenotype, which may be in turn likely secondary to long-term methotrexate use (i.e. methotrexate-associated lymphoproliferative disorder, MTX-LPD) or underlying autoimmune disease.
Conclusions PERM often has a paraneoplastic aetiology and likely exerts antitumour response against malignancies, thus potentially rendering the primary malignancies indolent or atypical in presentation. This is, to our knowledge, the first reported association between PERM and MBL, or between PERM and MTX-LPD.
