Cariotipo en la era del aCGH: – Neuropediatoolkit

Indications dans lesquelles le caryotypage reste supérieur aux techniques de diagnostic moléculaire :

Caractéristiques phénotypiques typiques d'un syndrome chromosomique spécifique (par exemple Down).

Petite taille, retard de puberté, aménorrhée ou organes génitaux ambigus (pour exclure aneuploïdies et mosaïques de chromosomes sexuels).

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1.
Bharat R, Unnikrishnan AG, Thampy MV, Anilkumar A, Nisha B, Praveen VP et al. Le syndrome de Turner et ses variantes. Indian J Pediatr [Internet]. 2010 [cité le 24 septembre 2022];77(2):193-5. Disponible à partir de : http://link.springer.com/10.1007/s12098-009-0226-7

Mort fœtale, mort néonatale et avortement (pour exclure aneuploïdie).

Couples ayant des antécédents d’infertilité ou d’avortements à répétition (pour exclure des translocations équilibrées : réarrangements chromosomiques réciproques o investissements).

Tout comme les translocations réciproques, la plupart des inversions sont héréditaires et ne sont pas associées à un phénotype clinique, mais les porteurs courent un risque accru de produire des gamètes anormaux et des problèmes de fertilité associés en raison du croisement d'événements de méiose impliquant le segment inversé.

Antécédents familiaux d'anomalies chromosomiques détectées par des méthodes cytogénétiques (variantes de l'hétérochromatine, etc.).

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1.
Liehr T. Variations du nombre de copies cytogénétiquement visibles (CG-CNV) dans les bandes et la cytogénétique moléculaire des humains ; sur les hétéromorphismes et les variantes euchromatiques. Mol Cytogenet [Internet]. 22 janvier 2016 [cité le 24 septembre 2022] ; 9 : 5. Disponible à partir de : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4724132/

Quand aCGH détecte une trisomie d'un chromosome acrocentrique (notamment 13 et 21), cela peut être le résultat d'une trisomie libre (qui est le plus souvent sporadique) ou d'une Translocation Robertsonienne parental (associé à un risque accru de récidive).

Quand l'ACGH détecte une délétion et une duplication sur le même chromosome.

Il peut être indicatif d'une inversion péri-centrale parentale, il faudra donc réaliser un karyotype des parents.

Quand nous soupçonnons des altérations structurales chromosomiques sans alteration du nombre de copies.

Investissements.
Chromosomes in ring.
Chromosomes idicéntriques (idic15).

Microcéphalie et petite taille sévère, ou bien réarrangements chromosomiques complexes, pour éliminer l'anéuploïdie variée mosaic, syndrome de Nijmegen.