Concurrent diagnoses of treatment-induced neuropathy of diabetes and restless leg syndrome

Background: To describe the clinical manifestations, treatment, and prognosis of a patient with type 1 diabetes (T1D) and concurrent diagnoses of painful treatment-induced neuropathy of diabetes (TIND) and restless leg syndrome (RLS). Case report: A 36-year-old man with newly diagnosed T1D experienced the onset of painful lower extremity neuropathy symptoms after a hemoglobin A1C drop from 15% to 6.6% over 1 month upon initiation of insulin pump therapy. His pain was refractory to conventional diabetic neuropathy management, and TIND was diagnosed given the rapid A1C reduction. He was later found to have anemia and diagnosed with concurrent RLS, for which he was treated with carbidopa-levodopa and later pramipexole. Over the course of 18 months, his neuropathic symptoms resolved completely. Discussion: TIND and RLS are both small fiber neuropathies with some shared clinical symptoms, including worsening symptoms at night. Sleep disturbance and the urge to move legs are more characteristic of RLS. Rapid A1C lowering, which may occur in patients with newly diagnosed T1D, may provoke TIND, while underlying iron-deficiency anemia is a risk factor for RLS. TIND may be poorly responsive to conventional diabetic neuropathy treatment and may take months to improve or resolve, while RLS is responsive to treatment with dopamine agonists. Conclusion: TIND should be suspected in T1D patients who have rapid A1C lowering (more than 2% drop in 3 months). In patients with refractory symptoms who have underlying iron deficiency anemia, sleep disturbance, and the urge to move their legs, RLS should be considered in the differential.