0987 Asking the Right Questions: A Case of Restless Legs Syndrome and Spinal Muscular Atrophy

Abstract

Abstract Introduction The association between iron deficiency and restless legs syndrome (RLS) is well established. However, there is limited data on the association between motor neuron diseases such as spinal muscular atrophy (SMA) and RLS. A forty-three-year-old with Type 2 SMA presented to clinic for management of chronic respiratory failure. She had recently undergone surgery and chemotherapy for newly diagnosed anal cancer. However, she reported persistent abdominal pain, anorexia, weight loss, and rectal bleeding. She reported “muscle twitching” and bilateral lower extremity pain and tingling that was worse at night. Her husband would awaken every 2 hours to massage her legs. She assumed these symptoms had emerged as a result of an increase in motor function due to risdiplam, a survival motor neuron 2 splicing modifier drug. Further questioning led to the diagnosis of RLS. Bloodwork revealed severe iron deficiency anemia (hemoglobin of 6.0 g/dL, iron 13 mcg/dL, and ferritin 3 ng/ml). She received a blood transfusion and underwent sigmoidoscopy for evaluation of cancer recurrence given the report of bleeding. Fortunately, her cancer remained in remission. Her symptoms of RLS significantly improved after blood transfusions and iron supplementation. Report of case(s) n/a Conclusion RLS is a complex sensorimotor syndrome. The diagnosis of RLS is clinical, relying on diagnostic criteria that requires lower extremity movement. The case is a reminder of the variable presentation of RLS in individuals with neuromuscular disorders, including SMA. How are symptoms of restless legs disclosed in patients with the inability to move and with potentially altered sensorium? The focus of the patient encounter could have anchored on the common and expected sequalae of SMA, chronic respiratory failure. Unfortunately, anchoring bias would have delayed the diagnosis and treatment of what could have been a potentially fatal disease – metastatic cancer. Ironically, the patient’s longing for motor function repressed her ability to lament. To the patient, symptoms of frequent nighttime awakenings and limb discomfort were perceived as a desired side effect of a medication that would increase movement. This case emphasizes the importance of the patient interview and its value of uncovering subtle complaints that may broaden the differential diagnosis and guide further work-up. Support (if any)