No abstract

A mass spectrometry approach for the detection and identification of variants of the plasma protein transthyretin (TTR) is presented. The single amino acid substitutions found in TTR are closely associated with familial transthyretin amyloidosis (ATTR), a hereditary degenerative disease. A definitive diagnosis of ATTR relies on the detection and identification of TTR variants. The approach presented here is based on isolation of serum TTR using immunoprecipitation. The detection of the variant is achieved by mass measurement of the intact protein with electrospray ionization mass spectrometry (ESIMS). The liquid chromatography/ESIMS analysis of the tryptic digest of the protein followed by subsequent matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry and MALDI postsource decay of the relevant recovered chromatographic fraction containing the variant peptide allows the identification of unknown variants. The method was successfully tested using serum from ATTR patients with known variants (Val30-->Met and Val122-->Ile). A new TTR variant, Ser23-->Asn, was detected and identified using the above method where isoelectric focusing and restriction enzyme analysis failed to identify the nature of the variant.

We report a 69-year-old woman of Mexican origin with a 6-year history of progressive paresis, mild peripheral neuropathy, and recent onset of fluctuating mental status. Head and spinal MRI revealed contrast enhancing thickened meninges which on biopsy disclosed amyloid deposition. Immunohistochemistry identified the amyloid as transthyretin (TTR), and polymerase chain reaction/restriction fragment length polymorphism analysis of blood revealed a Val30Met mutation in one of her TTR genes. This mutation causes familial (hereditary) amyloidotic polyneuropathy of the Portuguese type (FAP 1). However, unlike FAP 1, in which peripheral neuropathy is a dominant feature, our patient's clinical manifestations, which included communicating hydrocephalus and myelopathy, were more suggestive of familial oculoleptomeningeal amyloidosis (FOLMA). In summary, the clinical presentation of TTR Met 30 mutation is more varied than previously suspected, and leptomeningeal amyloidosis should be considered in the differential diagnosis of obscure conditions involving meninges.

Patients with X-linked lymphoproliferative (XLP) disease are characterized by extreme vulnerability to Epstein-Barr virus (EBV). Following infection with EBV, affected males develop fatal infectious mononucleosis (IM), hypogammaglobulinemia (H), or non-Hodgkin's lymphoma (NHL). In addition, hyper IgM, red cell aplasia, necrotizing lymphoid vasculitis (NLV), and aplastic anemia occur rarely. The recent use of DNA restriction fragment length polymorphism (RFLP) probes in linkage with the XLP gene now permit detection of affected males prior to primary EBV infection. We have measured immunoglobulin class and subclass levels in sera from EBV-negative males who were either positive or negative for the XLP genotype by RFLP analysis. Elevated IgA or IgM and/or variable deficiency of IgG, IgG1, and IgG3 occurred in the sera of 13/13 RFLP-positive, EBV-negative males. No consistent abnormalities were noted in 14 RFLP-negative, EBV-negative males. We conclude that the immune defect in XLP is not solely EBV-specific, although EBV is responsible for most of the morbidity and all of the mortality. Further, serial measurement of Ig levels may provide information regarding status of EBV-negative males at risk where RFLP analysis is uninformative or in families where sporadic cases of fatal IM, acquired hypogammaglobulinemia or NHL have occurred, but wherein the genotype of XLP cannot be documented.