Prevailing theories suggest that the syndromes are caused by viral infections, autoimmune disorders, or both. Importantly, approximatey 15 percent of adults who develop dermatomyositis have an associated malignant tumor. The timing of myositis and tumor appearance may be separated by several years. he most common sites of associated cancer are breast, lung, stomach, and ovary. The disease usually responds to high-dose corticosteroid therapy, immunosuppressive drugs such as azathioprine or methotrexate, or IVIG (Dalakas, 2012; Linardaki, 2011).
Experiences in pregnancy are garnered mostly from case series and reviews. Chen and colleagues (2015) found 17 women with polymyositis/ dermatomyositis in an Australian population-based cohort of births. These women had higher rates of hypertension (23 percent), antepartum hemorrhage (11 percent), cesarean delivery (88 percent), and preterm birth (35 percent). Another series of 60 women with dermatomyositis and 38 with polymyositis found that in 80 percent, pregnancy had no adverse efect on their disease. Similar results have been reported by others (Missumi, 2015; Pinal-Fernandez, 2014). Rosenzweig and colleagues (1989) reviewed 24 pregnancy outcomes in 18 women with primary disease. Of these, a fourth had an exacerbation in the second or third trimester. In 12 in whom disease became manifest first during pregnancy, half of the eight pregnancies resulted in perinatal death, and one woman died postpartum.
From their review, Doria and associates (2004) concluded that pregnancy outcome was related to dermatomyositis activity and that new-onset disease was particularly aggressive.
Numerous inherited mutations involve genes that encode for structural proteins of bone, skin, cartilage, blood vessels, and basement membranes. Although connective tissues contain many complex macromolecules such as elastin and more than 30 proteoglycans, the most common constituents are ibrillar collagen types I, II, and III. Various mutations, some recessively and some dominantly inherited, result in clinical syndromes that include Marfan and Ehlers-Danlos syndromes, osteogenesis imperfecta, chondrodysplasias, and epidermolysis bulla. Of concern during pregnancy is the predilection for these disorders to result in aortic aneurysms (Schoenhof, 2013).
This is an autosomal dominant connective tissue disorder that has a population prevalence of 1 in 3000 to 5000 (Prockop, 2015). Marfan syndrome afects both sexes equally. The syndrome is due to abnormal fibrillin-a constituent of elastincaused by any of several diferent mutations in the FENI gene (Biggin, 2004). Located on chromosome 15q21, the FENI gene has a high mutation rate, and there are many mild, subclinical cases. A 50-percent risk of disease transmission to the ofspring exists, however, the ability to predict disease severity in progeny is limited by the lack of distinct genotype-phenotype correlation and large clinical variability. Currently, preimplantation and prenatal diagnoses are limited to the 80 percent of cases in which the mutation in the FBNI gene is known (Smok, 2014).
In severe disease, there is degeneration of the elastic lamina in the media of the aorta. his weakness predisposes to aortic dilation or dissecting aneurysm, which appears more commonly during pregnancy (Curry, 2014; Roman, 2016). Marfan syndrome complicating pregnancy is discussed in more detail in Chapter 49 (p. 967).