PMC10453946_01
SGCE myoclonus-dystonia: autosomal dominant transmission with reduced penetrance. The patient pedigree was simplified for privacy. The patient is indicated by the arrow. The patient's brother and female cousin were symptomatically affected with myoclonus but did not undergo confirmatory genetic testing. The patient's grandmother (generation I) was likely the carrier of a maternally imprinted pathogenic SGCE allele that upon transmission to generation II was again maternally imprinted and silenced. However, once paternally transmitted by the patient's father and uncle, the autosomal dominant transmission pattern re-emerges in generation III. In generation IV, there is only a 2.5% chance each of the patient's young daughters will be affected in their lifetime due to maternal imprinting.
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F1
Her family history was remarkable for similar jerky upper body movements in her brother and a female cousin, but in no family members in prior generations (Figure 1).
PMC10453946_02
A genetics pearl for counseling patients with SGCE myoclonus-dystonia: Penetrance of the SGCE pathogenic variant differs for children of male versus female carriers.
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F2
Figure 2 depicts and summarizes the counseling provided above as a concise genetics pearl for reference in the clinic.