Essentially pure partial trisomy 6(p21.31-p25) (case report and literature review)

Abstract

Background: In reviewed literature, several patients with duplication or partial trisomy of the 6p region have been described. Most of these cases are associated with a partial monosomy of another chromosome. It has been suggested that partial trisomy 6p constitutes a well-defined syndrome. The aim of the study: To achieve a better clinical delineation of the 6p syndrome through the description of a patient with partial trisomy 6(p21.31-p25) comparing his characteristics with international reports and to discuss aspects of the phenotype of this syndrome. Materials and methods: A detailed clinical analysis of the patient’s condition was performed. The chromosomes were studied through the GTG-banding analysis. Results: On clinical examination we observed: a small anterior fontanel; fine, sparse and very pale hair, almost white hair; very white, translucent and thin skin; pale and sparse eyebrows and eyelashes; very narrow palpebral fissures with palpebral ptosis (blepharophimosis); a high nasal bridge, and straight nose with tiny nostrils; low implantation of the ears; microcephaly, neurodevelopmental and psychomotor delay; long philtrum, thin lips, the upper lip almost inverted and the mouth is small. From the neurological point of view there was evidence of trunk hypotonia and limb hypertonia. These are all typical features of trisomy 6p syndrome. A cytogenetic study of the patient and his father showed that trisomy 6p was due to an adjacent segregation I in paternal gametogenesis as the father is a 6,16-translocation carrier. Conclusion: The possible critical region is difficult to determine due to the clinical heterogeneity present in this syndrome. However, this case should be analyzed by molecular methods to determine more precisely the extent of the area involved in the trisomy.