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August 2000

Two Expanded Repeats in the Same Patient: An Effect on Phenotype?

Arch Neurol. 2000;57(8):1110-1112. doi:10.1001/archneur.57.8.1110

IN THIS issue of the ARCHIVES, Nokelainen et al1 describe a remarkable patient with 2 different diseases, each caused by an expanded repeat sequence. The first disorder, progressive myoclonus epilepsy of Unverricht-Lundborg type 1 (EPM1), produced in this patient nightly myoclonic jerks beginning at age 8 years and generalized seizures beginning at age 14 years. Interictal electroencephalographic findings were typical for EMP1 with generalized slowing and spike-and-wave or polyspike discharges with photomyoclonus. She also had a mild mental defect with dementia progressing slowly by age 25 years to the stage of "mild mental retardation (IQ class 50-69)." Findings of brain magnetic resonance imaging showed generous subarachnoid spaces, deep sulci, and wide Sylvian fissures with thickened bony skull structure. The second disorder in this patient, myotonic dystrophy (DM), became symptomatic in the second decade of life and was ultimately characterized by difficulty walking, scoliosis, ocular ptosis, atrophy of anterior neck muscles, facial weakness, distal limb weakness, hand muscle wasting, and attacks of atrial fibrillation. Myotonia and cataracts were absent, but electromyographic findings were positive for DM.

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