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Aplasia cutis congenita (ACC) is an uncommon condition in which localized or widespread areas of skin are absent or scarred at birth. There is no single underlying cause of ACC, as it simply represents a physical finding that reflects a disruption of intrauterine skin development. Here we report three cases of ACC of the scalp with three different etiologies: congenital rubella syndrome, trisomy 13 and fetal valproate syndrome. The aim of the present report is to increase awareness of these skin defects and emphasize the importance of underlying etiologies.

Subtelomeric rearrangements are an important cause of both sporadic and familial idiopathic mental retardation (MR) and/or congenital malformation syndromes. We report on a cohort of 107 children with idiopathic MR and normal karyotype 450-550 band level by GTG banding screened for subtelomeric rearrangements by multiprobe fluorescence in situ hybridization (FISH). In these cases, five patients had de novo deletions (1p deletion was found in 2 cases; 3q deletion, 9p and 9q deletions were found in 1 case each) and four patients had unbalanced rearrangements [der(5)t(5;15)(pter;qter)pat in 2 patients who were siblings, rec(10)dup(10p)inv(10)(p13q26)mat in 1 patient and der(18)t(18;22)(qter;qter) de novo in 1 patient]. Our study confirms that the subtelomeric rearrangements are a significant cause of idiopathic MR with dysmorphic features.

We report a newborn girl with multiple congenital anomalies whose chromosomal analysis showed complete trisomy 22. Her phenotype included microcephaly, epicanthus, hypertelorism, micrognathia, cleft palate, microtia, and preauricular tag. She died in the 24th post-natal hour. Trisomy 22 was shown by fluorescence in situ hybridization technique and the parental origin of the extra chromosome was found to be maternal by DNA microsatellite marker analysis of chromosome 22. Postmortem examination revealed the presence of atrioseptal defect and stasis in the biliary canals. We believe that this patient will contribute to the literature both by clinical findings and short life span associated with maternal origin of extra chromosome 22.

A case with de novo interstitial deletion of chromosome 7q21.1-q22: A patient with multiple congenital anomalies was found to have a de novo proximal interstitial deletion of chromosome 7q21.1-q22. The patient was 10.5 years of age, and manifestations include growth retardation (below 3rd percentile), mental retardation, mild microcephaly, hypersensitivity to noise, mild spasticity, short palpebral fissures, alternant exotropia, compensated hypermetropic astigmatism, hypotelorism, hypoplastic labia majora and minora, clinodactyly of fingers 4 and 5. Molecular studies revealed that the deletion had a paternal origin, while chromosomes of both parents cytogenetically were shown to be normal. Molecular, and fluorescence in situ hybridization (FISH) analyses confirmed no deletion at the Williams-Beuren Syndrome region. Some of the heterogeneous clinical findings were consistent with previously reported cases of same chromosomal breakpoints.

Until recently, presence of de novo marker or derivative chromosomes was quite problematic for genetic counseling especially in prenatal diagnosis, because characterization of marker and derivative chromosomes by conventional cytogenetic techniques was nearly impossible. However, recently developed molecular cytogenetic technique named Multicolor Fluorescence in Situ Hybridization (M-FISH) which paints all human chromosomes in 24 different colors allows us to characterize marker and derivative chromosomes in a single hybridization. In this study, we applied M-FISH to determine the origin of 3 marker and 3 derivative chromosomes. Marker chromosomes were found to originate from chromosome 15 in two postnatal and one prenatal case. Of these, one of the postnatal cases displayed clinical findings of inv dup (115) syndrome and the other of infertility, and the prenatal case went through amniocentesis due to the triple test results. Karyotypes of the patients with derivative chromosomes were designated as 46,XY,der (21)t(1;21)(q32;p11), 46,XX,der(8)t(8;9)(p23;p22) and 46,XX,der(18)t(18;20)(q32;p11.2) according to cytogenetic and M-FISH studies. All of the M-FISH results were confirmed with locus specific or whole chromosome painting probes. The case with der (8)t(8;9) had trisomy 9(p22-pter) and monosomy 8(p23-pter) due to this derivative chromosome. The case with der(18)t(18;20) had trisomy 20(p11.2-pter) and monosomy 18(q32-qter). Parental origins of the derivative chromosomes were analyzed using microsatellite markers located in the trisomic chromosomal segments. Patients' clinical findings were compared with the literature.