Rozenova, Krasimira

Abstract Background Multiple laboratory tests are employed for detection of monoclonal proteins in patients and include serum protein electrophoresis (SPEP), immunofixation electrophoresis, free light chain (FLC) immunoassay, and mass spectrometry (Mass-Fix). Recently, reports on a drift in FLC quantitation results have been brought to light. Methods We studied a cohort of 16 887 patients whose sera were tested for a monoclonal protein by a FLC assay, serum protein electrophoresis, and Mass-Fix. This is a retrospective study designed to assess the impact of a drift on the performance of FLC ratio (rFLC) in groups of patients with and without detectable plasma cell disorders (PCDs). Results The results demonstrated that 63% of patients with monoclonal protein equal or higher than 2 g/L (by SPEP) had an abnormal rFLC (reference range 0.26–1.65). Conversely, 16% of patients with undetectable monoclonal protein by other methods (i.e., SPEP and Mass-Fix) who also had no record of treated PCD had an abnormal rFLC. In these cases, there was an imbalance in the number of kappa high rFLCs to lambda low rFLCs of 201 to 1. Conclusions The results of this study suggest decreased specificity of rFLC for a monoclonal kappa FLC in the 1.65 to 3.0 range.

AbstractLafora disease is a rare inherited neurodegenerative disease with onset in adolescence. Patients present with progressive myoclonic seizures and cognitive decline. The disease is linked to mutations in either of the two genes encoding malin and laforin, and it is associated with the accumulation of polyglucosan inclusions (Lafora bodies [LBs]) in various tissues, such as brain, liver, muscle, and skin, with the skin being particularly accessible for biopsy. Histopathologic examination of affected tissue with demonstration of LBs, together with the presence of pathologic mutation in EPM2A or NHLRC1 genes, is sufficient for diagnosis of this neurologic disorder when clinically suspected. Here, we report the case of a 16‐year‐old female with progressive neurologic symptoms and homozygous mutation in the NHLRC1 gene encoding malin. The skin biopsy was instrumental in reaching the final diagnosis by showing LBs in sweat glands by histopathologic and electron microscopic examination.