RESUMO
Autoimmune diseases are not found frequently with pregnancy in clinical practice. Polymyositis Dermatomyositis have a prevalence of 2.4-10.7/ 100,000 in general population. This is further low in pregnant women. It is associated with 57% perinatal morbidity and increased maternal and fetal mortality. Literature suggests that pregnancy outcomes are poorer if it manifests early in gestation while development or exacerbation in second or third trimester is associated with a better fetal prognosis. Not many case reports are published where the disease was diagnosed in third trimester. We present a case detected in third trimester, which was initially mistaken as a case of allergic reaction, however timely diagnosis and adequate management resulted in good fetal and maternal outcome.