A patient with 2 different repeat expansion mutations.
BACKGROUND
Many inherited progressive encephalopathies have a poor outcome, and some are caused by repeat expansion mutations. How would the presence of 2 different expansion mutations affect the phenotype?


OBJECTIVE
To describe a patient who has 2 distinct, rare genetic disorders: myotonic dystrophy (DM, OMIM 160900) and progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1, OMIM 254800). Both conditions are caused by repeat expansion mutations. They affect the central nervous system causing mental retardation, but also produce a wide spectrum of disabilities in daily living.


METHODS
Referral center.


METHODS
Clinical description with accompanying photographs, electroencephalography and magnetic resonance imaging; DNA analysis of both of the mutations and chromosomal analysis with prometaphase spreads.


RESULTS
The patient had clinical characteristics and findings of both myotonic dystrophy and progressive myoclonus epilepsy of the Unverricht-Lundborg type. Electroencephalographic recordings over a 3-year period showed typical findings for myoclonus epilepsy. The patient had no gross anomalies in brain magnetic resonance imaging. She had a normal karyotype, and both of the diagnoses were confirmed at the molecular level with the direct detection of the mutations.


CONCLUSIONS
Despite having 2 different progressive inherited disorders affecting the central nervous system, the patient, at age 28 years, showed only mild mental retardation with very slow progression. However, clear deterioration in activities of daily living has taken place during last 3 years. Arch Neurol. 2000;57:1199-1203
Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DU, England. pnokelai@molbiol.ox.ac.uk
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P
Nokelainen
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H
Heiskala
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Lehesjoki
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M
Kaski
D000328:Adult; D015139:Blotting, Southern; D055313:Cystatin B; D015891:Cystatins / Q000235:genetics; D004252:DNA Mutational Analysis; D004576:Electromyography; D005091:Exons / Q000235:genetics; D019066:Facies; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics*; D008279:Magnetic Resonance Imaging; D009223:Myotonic Dystrophy / Q000175:diagnosis / Q000235:genetics*; D065636:Myotonin-Protein Kinase; D010375:Pedigree; D010641:Phenotype; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D019680:Trinucleotide Repeat Expansion; D020194:Unverricht-Lundborg Syndrome / Q000175:diagnosis / Q000235:genetics*
C524994:CSTB protein, human; D015891:Cystatins; C585517:DMPK protein, human; D055313:Cystatin B; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases