Women with MuSK-MG Can Have Safe Pregnancies, Small Study Suggests

Women with a rare form of myasthenia gravis (MG) called muscle specific kinase (MuSK) MG can have healthy pregnancies without jeopardizing outcomes or increasing the risk of disease worsening, a small group study suggests.

The study, “MuSK Myasthenia gravis and Pregnancy,” was published in the journal Neuromuscular Disorders.

MuSK-myasthenia gravis (MuSK-MG) primarily affects women in their childbearing years, but how pregnancy affects the course of disease remains largely unknown. Equally unknown is the outcome of pregnancies in women affected with MuSK-myasthenia gravis.

Researchers conducted a retrospective study of 17 women diagnosed with MuSK-myasthenia gravis from seven hospitals located in northern Portugal.

Thirteen of the 17 women had at least one pregnancy, and their mean age was around 35 at the time of disease onset. Forty-six percent of them were refractory (resistent) to treatment, and 23% suffered from other autoimmune disorders.

In total, the 13 women experienced 27 pregnancies, with the majority (23) occurring before MuSK-myasthenia gravis onset; only four pregnancies happened after the disease was diagnosed.

In the group of four women who became pregnant after the disease manifested, all were medicated with Mestinon (pyridostigmine bromide) and steroids at the time of conception. Two of them were treated with additional therapies.

The analysis showed that pregnancy had no major effects on the disease course. Only one patient experienced moderate worsening – from class IIB to class IIIB – while the remaining women had mild exacerbations.

This, authors wrote, was “probably because the pregnancy occurred many years after the MG onset when the disease was already on treatment, and stable, for a long period of time.”

These results suggest that pregnancy has no detrimental effects in women with MuSK-MG, but the study should be viewed with caution “as it is a small series of four patients,” the researchers wrote.

Neither the disease itself nor its treatment seemed to influence pregnancy outcomes negatively, as it did not cause complications such as “miscarriages, pre-eclampsia, birth defects, intrauterine growth retardation, hydramnios [too much amniotic fluid], fetal akinesia [loss of voluntary movement], or stillbirths.”

In women where pregnancy preceded the onset of disease, the pregnancies occurred on average 17 years before the disease was diagnosed. Previous studies identified pregnancy and the postpartum period as a risk factor for MuSK-MG. In this group, however, “pregnancy did not seem a precipitating factor for the development of MuSK-MG.”

Overall, these findings suggest that women with MuSK-MG can undergo healthy pregnancies, and the disease can be controlled during this period. Future studies with larger groups of women are required to confirm these findings.

“Close monitoring and appropriate management by experienced obstetricians, pediatricians and neurologists will be, however, required,” the authors concluded.