Maternally Inherited Diabetes and Deafness (MIDD) Syndrome Associated with Myoclonus (P07.148)

Objective: Maternally inherited diabetes and deafness (MIDD) syndrome is a rare mitochondrial disorder characterized by progressive sensorineural hearing loss and diabetes mellitus. Case reports also exist of patients with additional clinical features typically associated with mitochondrial disorders, such as retinopathy, seizures, and stroke-like episodes. We present the clinical, imaging, histopathologic and genetic data for a patient diagnosed with MIDD following evaluation for new-onset myoclonus. To our knowledge, this is the first case to describe MIDD syndrome in association with myoclonus. Background MIDD syndrome is a mitochondrial genetic disorder caused by a heteroplasmic A3243G transition of mtDNA. The same mutation has also been associated with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS). It has not been previously associated with myoclonus. Design/Methods: We report the clinical characteristics of a patient diagnosed with MIDD syndrome after initially seeking medical attention for myoclonus, and present the results of a comprehensive literature review. Results: A 57-year-old man developed intermittent myoclonic jerks in his right arm. He had a past history of sensorineural hearing loss developing in his late 20s, and diabetes mellitus developing in his 30s. On exam, he was found to have subtle proximal muscle weakness, as well as peripheral neuropathy. EEG demonstrated rare generalized spike-and-wave discharges. He was started on valproic acid, with resolution of myoclonus. Subsequently, a muscle biopsy demonstrated ragged-red fibers. Genetic testing confirmed the A3243G mtDNA mutation. Given his clinical picture, a diagnosis of MIDD syndrome was established. Conclusions: MIDD syndrome should be considered in patients presenting with a clinical syndrome of sensorineural hearing loss and diabetes mellitus. Additional features of mitochondrial disorders, such as myopathy, neuropathy, and myoclonus may be present. Valproic acid may be an effective treatment of myoclonus. In addition, treatment with coenzyme Q10 may be of modest benefit in slowing progression of neurologic deterioration. Disclosure: Dr. Blondin has nothing to disclose. Dr. Vortmeyer has nothing to disclose. Dr. Tokuno has nothing to disclose.