Pregnancy in Patients With McArdle's Disease

The influence of hereditary disorders of metabolism in pregnancy can be unclear, probably due to their rarity. McArdle's disease does not have an impact on fertility; therefore, some cases of pregnancy have been reported in patients with McArdle's disease. This article reviews published cases of pregnant women with McArdle's disease, focusing on the period of pregnancy, delivery, and postpartum. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), the authors conducted a literature search of PubMed, Web of Science, and Dialnet, as well as the journal Ata Portuguesa de Ginecologia e Obstetrícia (Journal of the Portuguese Societies of Gynecology and Obstetrics). The authors searched for articles in Portuguese, English, French, and Spanish using the combination of keywords "pregnancy" and any of the following: "McArdle's Disease", "Type V Glycogenosis", or "Myophosphorylase", available as of February 18, 2023. Thirteen articles corresponded to the search criteria, describing a total of 26 patients with McArdle's disease and 37 pregnancies (one of them a twin pregnancy). No case reports or case series were excluded. The objective was to evaluate obstetric index, comorbidities, gestational age, description of pregnancy evolution, mode of delivery, intrapartum pharmacological measures, and clinical evolution in the postpartum period. Of the 16 cases in which age of the patient was mentioned, the mean age was 27.75 years. Of the 18 cases in which the obstetric index was mentioned, 13 (72.2%) pregnancies were first pregnancies and 5 (27.8%) were second pregnancies. In addition to McArdle's disease, some patients had other comorbidities: one had Crohn's disease; one had dilated cardiomyopathy; one had grade II obesity; one had arterial hypertension, dyslipidemia, gastroesophageal reflux disease, and grade III obesity; and one had recurrent tonsillitis and allergic rhinitis. The mean age of pregnant women was 27.75 years. In most cases (75.7%), there was no mention of complications during pregnancy. There were four (10.8%) cases of rhabdomyolysis (two triggered by infectious diseases, one by exercise, and one with no evident trigger). Two women developed gestational diabetes, one had pre-eclampsia, one patient with dilated cardiomyopathy had worsening complaints of heart failure, and one patient developed idiopathic thrombocytopenia, which resolved after delivery. Of the 18 patients questioned about tolerance to exercise, two (11.1%) reported worsening of myalgia during pregnancy, while the rest reported symptomatic improvement. In 16 cases, it was necessary to perform a cesarean section. The remaining 22 deliveries were vaginal. Of the 14 cases in which anesthesia was specified, 12 (85.7%) patients were given epidural and 2 patients were given general anesthesia. There were three reported cases of rhabdomyolysis after childbirth. Pregnancy in patients with McArdle's disease does not seem to be associated with more complications than pregnancy in women without the disease, and there may even be an improvement of the symptoms during pregnancy. This review will help physicians provide such patients with better counseling and take measures to prevent complications. Implementing protocols designed specifically for pregnancy, delivery, and postpartum in patients with McArdle's disease could be beneficial, reducing the episodes of rhabdomyolysis.