RESUMO
Leukodystrophies are rare genetic white matter disorders that have been regarded as mainly occurring in childhood. Recent years altered this perception, as a growing number of leukodystrophies was described to have an onset at adult ages. Still, many adult patients presenting with white matter changes remain without a specific molecular diagnosis. We describe a novel adult onset leukodystrophy in 16 patients from eight families carrying one of four different stop-gain or frameshift dominant variants in the CST3 gene. Clinical and radiological features differ markedly from the previously described Icelandic Cerebral Amyloid Angiopathy that was found in patients carrying p.Leu68Asn substitution in CST3. The clinical phenotype consists of recurrent episodes of hemiplegic migraine associated with transient unilateral focal deficits and slowly progressing motor symptoms and cognitive decline in mid-old adult ages. In addition, in some cases acute onset clinical deterioration led to a prolonged episode with reduced consciousness and even early death. Radiologically, pathognomonic changes are found at typical predilection sites involving the deep cerebral white matter sparing a periventricular and directly subcortical rim, the middle blade of corpus callosum, posterior limb of the internal capsule, middle cerebellar peduncles, cerebral peduncles, and specifically the globus pallidus. Histopathologic characterization in two autopsy cases did not reveal angiopathy, but instead micro- to macrocystic degeneration of the white matter. Astrocytes were activated at early stages and later on displayed severe degeneration and loss. In addition, despite loss of myelin, elevated numbers of partly apoptotic oligodendrocytes were observed. A structural comparison of the variants in CST3 suggests that specific truncations of Cystatin C result in an abnormal function, possibly by rendering the protein more prone to aggregation. Future studies are required to confirm the assumed effect on the protein and to determine pathophysiologic downstream events at the cellular level.
RESUMO
To carry out quality management of genetic counseling, it is important to know what genetic counseling exactly means and who the players are. The term "genetic counseling" was first defined by Reed in 1947. It describes a communication process dealing with genetic facts and psychosocial aspects and is an education process, too. It has always been understood in the context of individual and family problems, and is unrelated to eugenics. In 1975 the Ad Hoc Committee of the American Society of Human Genetics published a more detailed description. With the development of new diagnostic techniques and methods in human genetics, the requirements of genetic counseling and its contents changed. Today a genetic counselor has to apply diagnostic, predictive, susceptibility, pharmacogenetic, carrier, prenatal, and preimplantation testing, as well as genetic screening. The German Human Genetic Examination Act (Genetic Diagnosis Act - GenDG) and national and international associations recommend to embed genetic testing into genetic counseling. Based on experiences of the author, some examples of pitfalls in genetic counseling are illustrated, as there are so many individual situations and requests that it seems impossible to carry out quality management. Nevertheless, the Commission for Quality in Genetic Counseling and Clinical Genetics of the Professional Association of German Human Geneticists started a pilot ring trial in 2018 with a given counseling situation. The task was to write the human genetics comment with the help of a checklist containing all issues necessary. The evaluation was conducted with the help of a catalogue of criteria which had been established beforehand and a score adjusted to the individual situation. The first genuine pilot trial was launched in 2020. It represents a possibility for quality management in genetic counseling.