Increased levels of a nerve-growth-factor cross-reacting protein in "central" neurofibromatosis.

Nerve-growth factor (N.G.F.) from serum was assayed in 9 affected individuals from three kindreds with the trait "central neurofibromatosis". The hallmark of this disease is bilateral acoustic neuromas. Antigenic activity, as measured by radioimmunoassay, was significantly elevated. However, functional activity for N.G.F.; as measured by radioreceptor assay, was normal or low. This indicates that the central form of neurofibromatosis is characterised by high circulating N.G.F. levels which show low to normal function. These changes in N.G.F. differ from those in peripheral neurofibromatosis and suggest that the two hereditary conditions involve different alterations in N.G.F. synthesis and/or regulation.