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Familial motor neuron disease: differing penetrance in large pedigrees
D B Williams1, D A Floate, J Leicester
1Department of Medicine, University of Sydney, N.S.W., Australia.
Journal of the Neurological Sciences
|September 1, 1988
Summary
Familial motor neuron disease may be more common than previously thought due to reduced gene penetrance. Many cases are misdiagnosed as sporadic, underestimating the true incidence of inherited forms.
Area of Science:
- Neurology
- Genetics
Background:
- Motor neuron disease (MND) is a group of progressive neurodegenerative diseases.
- Familial forms of MND are thought to be rare, often requiring high penetrance for diagnosis.
Observation:
- Studied 9 families with familial MND, revealing significant variation in gene penetrance.
- One family showed high penetrance autosomal dominant inheritance.
- Other families exhibited diminished penetrance autosomal dominant inheritance.
Findings:
- Diminished penetrance in familial MND leads to a higher average age of onset.
- Gene carriers with low penetrance may die from other causes before disease onset.
- Low penetrance can result in misdiagnosis of familial cases as sporadic MND.
Implications:
- The incidence of familial MND is likely underestimated.
- Excluding cases with low penetrance familial disease skews incidence data.
- Average age of onset in familial MND may be higher than reported due to selective study of high-penetrance families.