F26 Identical twins .. Are they identical?

Background Reports of monozygotic HD twins are rare (Panas et al, 2008) and phenotypic concordance reported as the rule (Sudarsky et al, 1973). Reports are of twins with the same number of trinucleotide repeats, with different clinical behavioral difficulties but not significant motor differences (Gomed-Esteban et al, 2007). Such phenotypic discordance was reported as very rare (Friedman et al, 2005) and thus be used to explore environmental factors (Ketelaar, Hofstra and Hayden, 2012). Case History Two female monozygotic twins with HD were born 6 weeks premature and raised in the same environment. Voluntary predictive testing for HD was done when both (Heimler and Zanko, 1995) were aged 21 years. We will report on motor, neuropsychological and psychiatric manifestations along with MRI findings. Twin 2 required admission in 2015 while Twin 1 required admission in 2020. Twin 1 (first born): Referred to Liaison Psychiatry with Eating disorder and low mood aged 23, followed by two suicide attempts and aggressive impulsive behavior. Neurocognitive difficulties included memory impairment, dysarthria and balance difficulties, poor levels of motivation and self-care. OT assessment found a sensory level of activities and exploratory activities were required. MRI: Generalised and bifrontal cerebral atrophy appeared was unusual given the patient‘s age. There was no acute area of infarction on diffusion weighted imaging. Generalised cerebral and bifrontal cerebral atrophy noted. Twin 2: Diagnosed with a heart murmur aged 4 years and surgery aged 10 years. Presented at 18 years with low mood and history of OCD symptoms. Multiple episodes of self-harm and becoming more aggressive and violent. Irritability, impulsivity, and aggressive behavior has continued with word funding difficulties. OT assessment recommended exploratory level of activities. MRI: There was parenchymal atrophy reported, most marked in the frontal and temporal lobes with prominence of sulci and ventricles. Signal return from grey-white matter was normal. Conclusion A detailed comparison of motor, cognitive, and behavioural profile is currently in progress.