Review: Vigilance Warranted to Prevent, Treat Transient Neonatal Myasthenia Gravis

Transient neonatal myasthenia gravis (TNMG) is a rare—but potentially fatal—condition that affects some children of mothers who have MG. In a new review article, investigators wrote that the disease can be hard to predict, but preventive measures can be effective.

An estimated 10% to 20% of children born to mothers with MG will experience TNMG, they wrote.

The investigators reviewed articles about the condition, which were published between 1974 and September 2023, publishing their findings in Journal of Clinical Medicine.

As with adult cases of MG, the study authors said TNMG is characterized by fluctuating muscle weakness and fatigue. It is most commonly caused by acetylcholine receptor antibodies, but cases caused by muscle-specific kinase antibodies have also been reported, they said.

“TNMG should not be confused with congenital myasthenic syndromes, which comprise a heterogenous group of rare hereditary conditions caused by genetic defects in functionally important molecules at the neuromuscular junction,” the authors cautioned.

In addition, they said it should not be confused with juvenile MG, a disease in which symptoms typically do not start until around age 5.

Mother holding new born baby in her arms

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TNMG often presents itself at birth, and 80% of cases show symptoms within 24 hours postpartum, the authors said. On average, symptoms last 2 to 3 weeks, they noted, and 90% of children see complete resolution of symptoms within 2 months. The remaining 10% tend to recover within 4 months, they added.

Managing patients with TNMG will depend upon the severity of the symptoms, the authors said. “The majority of TNMG patients present with mild disease requiring only attention to feeding, and the baby can be discharged home after 3 days of observation,” they wrote.

They noted that breastfeeding can be difficult for newborns with TNMG, due to weak sucking and facial muscles; however, they said breastfeeding should still be encouraged unless contraindicated by the medications being taken by the mother. The investigators said one study found 76% of newborns with TNMG were able to successfully breastfeed.

In cases where pharmacological therapy is required, acetylcholine-esterase inhibitors can be used, as can intravenous immunoglobulin (IVIG) and therapeutic plasma exchange (TPE), in moderate and severe cases, Gilhus and colleagues said.

“All newborns to mothers with known MG should have access to prompt specialized neonatal evaluation and neonatal intensive care if needed,” the authors said, adding that all of the baby’s caregivers should be made aware of the signs of TNMG, and newborns of others with MG would ideally be observed in the hospital for 72 hours before discharge.

However, they also said careful planning can help prevent TNMG altogether. They said reducing circulating immunoglobulin G antibodies in the mother can reduce the antibody load in the child. Options to do that include IVIG, TPE, and neonatal fragment crystallizable receptor (FcRn) blockers. Prepregnancy thymectomy also has been found to lower the risk of TNMG. Women with MG and a previous child with TNMG or similar disorders are candidates for FcRn blockade, the authors said, “but the benefits need to be weighed against potential risks,” including a heightened risk of neonatal infections and fetal hypoalbuminemia.

IVIG and TPE monotherapy have been shown to be safe both before and during pregnancy, the investigators said, and are indicated in cases where a mother has previously had a child with TNMG or similar conditions.

The investigators said there is still much to learn about the disease, but that careful monitoring and management of mothers with MG can improve outcomes. They added that identifying a biomarker that could predict TNMG should be a goal of future research, as it would aid in making decisions about preventive measures.

Reference

Lindroos JLV, Bjørk MH, Gilhus NE. Transient neonatal myasthenia gravis as a common complication of a rare disease: a systematic review. J Clin Med. 2024;13(4):1136. doi:10.3390/jcm13041136