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Introduction
Monosomy 8p is a rare chromosomal disorder characterized by deletion of a part of the eighth chromosome. The incidence of the 8p23.1 deletion was estimated at 1:18,542 in amniotic fluid samples and 1:5,072 in postnatal samples (1). Since the first report of an 8p23.1 deletion by Fagan and Morris (2), >50 cases have been reported (3). The majority of the cases are not studied with high resolution molecular techniques or characterized at the molecular level (4). Interstitial deletions of the sub-band 8p23.1 have primarily been associated with facial and other phenotypic abnormalities, whereas terminal deletions are associated with heart defects (3,5). Notably, distal deletion of 8p23.2-pter has additionally been observed in apparently healthy individuals (1).
In the majority of cases, monosomy 8p appears to result from de novo errors in early embryonic development that occur for unknown reasons. Associated symptoms and findings differ between cases (6). However, in most cases clinical manifestations including growth deficiency, mental retardation, post-natal growth retardation, developmental delay and speech problems are observed. Furthermore, patients present with common signs of body and craniofacial dysmophisms, in addition to behavioral difficulties (1,3,5,6). Facial dysmorphisms, which are more remarkable in early years, include microcephaly, malformed or low set ears, arched eyebrows, depressed nasal bridge, epicanthus, strabismus, hypermetropia and/or myopia, serrated teeth, short neck and retrognathia. In addition, vertebral abnormalities are frequently observed (7–11).
It has additionally been reported that children with this chromosomal disorder present with behavioral difficulties, including aggressiveness and attention deficit disorder, and problems associated with cardiovascular and central nervous system (5,9,12). Furthermore, genito-urinary anomalies, in particular cryptorcidism and hypospadias, are observed in boys (6).
In contrast to 8p deletion syndrome, partial trisomies of the terminal 16qter are rare (1). A total of nine cases of partial distal chromosome 16 trisomy have been reported but only a few were studied with high resolution molecular techniques. Only one patient presented a pure partial trisomy 16q24.1q24.3, whereas all the others corresponded to unbalanced translocations where 16q24 was rearranged with other chromosome regions (7,8,10,11,13–15). For two of the patients, there was no detailed phenotypic information (10,15). A number of clinical characteristic features were common in all patients (low birth weight, growth retardation, intellectual disability, muscular hypotonia, small palpebral fissures, long philtrum, low set/dysplastic ears...