Acute leg pain and weakness in pregnancy: A new diagnosis of myotonic dystrophy.

We present a unique case of a 44-year-old woman who presented at 29 weeks' gestation with proximal limb pain and elevated creatine kinase. This occurred in the background of premature cataracts, atrial fibrillation and abnormal liver function. Clinical, pathological and neurodiagnostic findings supported a diagnosis of myotonic dystrophy, confirmed by genetic testing which revealed dystrophia myotonica protein kinase gene expansion. Muscle biopsy found both recent necrotising and chronic myopathic processes. Following delivery, the mother's myalgia resolved and creatine kinase quickly declined. The fetus was diagnosed with congenital myotonic dystrophy. We review the impact of myotonic dystrophy on pregnancy and discuss potential explanations for this patient's clinical course. This case emphasises the importance of considering myotonic dystrophy as a differential diagnosis in the right clinical context and the need for pre-pregnancy assessment and genetic counselling in women with known myotonic dystrophy.