Background: Tetrasomy 18p is a very rare chromosomal disorder and is the result of a spontaneous mutation early in embryonic development in most of the cases. This condition is characterised by the presence of a supernumerary 18p isochromosome (i(18p)) in all or some cells of the affected individual. It has a prevalence of 1/180000 live births and affects both genders equally.
Materials and methods: In this paper we report a de novo tetrasomy 18p in a 3 months old female dysmorphic child. The clinical features were distinctive with a particular facies, strabismus, microcephaly, growth delay, neonatal hypertonia and talipes varus. An additional small metacentric marker chromosome has been identified after standard cytogenetic analysis, without recognized parental origin of the supplementary genetic material. The child's parents were also tested and their karyotype results were normal. The characterization of the marker chromosome was performed in our genetics laboratory using conventional cytogenetic methods and Fluorescence in Situ Hybridization (FISH) analysis. Also, our patient was compared with other published cases with the same diagnosis.
Conclusion: Cytogenetic investigation is an essential step towards the accurate diagnosis of individuals with clinical suspicion of a genetic anomaly. Also, this type of investigation could offer critical information to the practitioner for prognosis of patient and the correct appreciation of the recurrence risk of a certain genetic condition.With current advances in preventive and interventional procedures, patients with rare chromosomal disorders can live longer. Therefore, proper medical and behavioural management of each case is important for the enhancement of the quality of life for the patients and their families.
Keywords: FISH; genetic counseling; isochromosome 18p; karyotype; rare disease.