alpha-Fetoprotein and neonatal transient myasthenia gravis

High-dose intravenous immunoglobulin in transient neonatal myasthenia gravis

A preterm newborn had transient neonatal myasthenia gravis and was mechanically ventilated for 9 days. In addition to the usual supportive care, she was treated with neostigmine and underwent two exchange transfusions. High-dose intravenous immunoglobulin therapy (2 gm/kg) was used for the first time in transient neonatal myasthenia gravis to the best of our knowledge. The clinical and laboratory responses are presented.

Transient neonatal myasthenia gravis

Transient neonatal myasthenia gravis is a postsynaptic neuromuscular transmission defect occurring in 21% of infants born to women with active (and, less commonly, in remission) acquired myasthenia gravis. Although passive-transfer acetylcholine receptor (AChR) antibodies are found in the majority of these newborns, their pathogenic role is questionable because only some infants are symptomatic. Pathogenesis in infants without AChR antibodies is unknown. There is still no biologic marker for prenatal identification of this subpopulation of newborns, although HLA typing may be a promising tool. Sucking, swallowing, and respiratory difficulties are the most common presenting signs in the first day of life. Final diagnosis is done when administration of acetylcholinesterase agents transiently corrects the neuromuscular transmission defect. Serum AChR antibody titers follow the same pattern as their mothers. Supportive management and anticholinesterase agents prior to feedings are necessary in about 80% of patients. In the majority of infants the condition resolves spontaneously.

Chemistry and biology of alpha-fetoprotein

Alpha-Fetoprotein (AFP) is a product of specific fetal tissues and of neoplastic cells of hepatocyte or germ cell origin in adults. This protein belongs to a gene family that is phylogenetically most closely related to serum albumin. Its primary, secondary, and tertiary structural aspects appear similar to the three-domain concept proposed for the latter protein. The primary sequence of AFP departs most widely from serum albumin in the first 135 amino acid residues, with about 42% of the remaining 590 residues of the human proteins being identical. Some evidence exists that there are limited sequence differences in the AFP of a given animal species. AFP shows considerable charge heterogeneity that appears to relate mostly to its glycoid moiety. The proteins of some species such as the rat show more pronounced heterogeneities than that of humans. The variations in extent and type of glycosylations are evidenced by differences in the binding to various lectins. These interactions are being extensively explored in attempts to differentiate the sources of the protein produced by various normal and neoplastic cells and may provide valuable diagnostic methods. AFP, like serum albumin, shows relatively strong binding affinities for a variety of ligands. The most notable difference is the strong preferential binding of polyunsaturated fatty acids by AFP. This protein may play a role in transporting these substances to developing and to malignant cells. Various agents affect the synthesis of this protein both by specific fetal tissues and by neoplastic cells. Marked differences in the responses of cells, particularly those of neoplastic types, are indicative of variations in the genetic factors responsible for control of its synthesis. The subject of the genomic repression of the synthesis of AFP seen in fetal life upon maturation of the liver and the reoccurrence of synthesis upon malignant conversion of hepatocytes and of certain germ cells are of particular interest. The regulation of the closely related AFP and albumin genes is providing a powerful and attractive model to examine molecular events in the activation and inactivation of specific genes during development and in oncogenic processes. Extensive measurements of AFP during pregnancy and in the course of neoplasias, notably hepatoma, are being made to aid in following changes in such developments. Various specific physiological roles for this protein are also being proposed. One of these is its possible action in the regulation of immune processes.(ABSTRACT TRUNCATED AT 400 WORDS)