A novel missense mutation (T719P) in the amyloid-beta protein precursor (AbetaPP) gene was discovered in a 46-year old patient affected by early onset familial Alzheimer's disease. Using surface enhanced laser desorption/ionization mass spectrometry (SELDI-TOF MS), we determined mass profiles of amyloid-beta peptides (Abeta) in cerebrospinal fluid (CSF) of the AbetaPP mutated patient, healthy control subjects (n = 10), and of two subjects carrying mutations in presenilins genes (PS) (i.e., PS1 P117L and PS2 T122R): seven different C-terminally and three N-terminally truncated Abeta peptides were found in CSF. The investigated AbetaPP as well as PS mutations were associated with an overall reduction of Abeta species, except for Abeta(10-40). Interestingly, the AbetaPP T719P mutation unbalanced the relative proportion of Abeta peptides with a reduction of Abeta(1-40) and Abeta(1-42) paralleled by an increase of Abeta(1-38) and Abeta(10-40). Despite the specific neuropeptidomic phenotype associated with the AbetaPP T719P mutation, the enrichment in Abeta(10-40) paralleled by depletion of Abeta(1-42) seems to be a common theme in familial AD. The AbetaPP T719P mutation is of particular interest because it is the only mutation located in close proximity to the AbetaPP epsilon-cleavage site.