Academic journal article Genetic Counseling

PARTIAL TRISOMY OF THE DISTAL PART OF 10q: A REPORT OF TWO EGYPTIAN CASES

Academic journal article Genetic Counseling

PARTIAL TRISOMY OF THE DISTAL PART OF 10q: A REPORT OF TWO EGYPTIAN CASES

Article excerpt

Summary: Partial trisomy of the distal part of 10q: A report of two Egyptian cases: Partial trisomy of the distal third of the long arm of chromosome 10 is a well defined but rare syndrome. Most cases result from an unbalanced translocation. Growth retardation, developmental delay and characteristic dysmorphic features are well described in the syndrome. This report includes 2 Egyptian cases with partial 10q trisomy involving different breakpoints. Cases were subjected to full clinical examination and detailed cytogenetic analysis using conventional and FISH studies. Results showed that the karyotype of case 1 was 46,XX,der(7)t(7;10)(p22;q23).ish(wcp7+;wcpl0+) and the karyotype of case 2 was 46,XX,der(7)t(7;10)(p22;q25).ish(wcp7+;wcpl0+). The chromosomal abnormalities in case 1 resulted from a paternal balanced translocation while case 2 resulted from a maternal balanced translocation involving chromosomes 10 and 7 in both cases. The probands' phenotypes were correlated to the breakpoints and compared to previously reported cases with partial trisomy 10q. Both cases had the well characterized phenotype of the distal trisomy of 10q in the form of mental retardation, microcephaly, characteristic dysmorphic facies and limb anomalies as trisomy in both cases involved the 10q25[arrow right]qter region. However, case 1 with 10q25[arrow right]qter duplication showed more severe clinical manifestations than case 2 with less extensive 10q25[arrow right]qter trisomy. These included severe failure to thrive, cardiac involvement and death from respiratory and heart failure. This study confirmed that unbalanced chromosome regions of the long arm of chromosome 10 play an important role in developmental malformations and that a more severe form is associated with involvement of 10q23. It also emphasizes the importance of increasing public awareness regarding these chromosomal rearrangements and the importance of genetic counseling and prenatal diagnosis to avoid recurrences and associated family stress. This was clearly demonstrated in the second family in this study as the couple refused any follow up or further investigations due to religious beliefs despite their social and educational level.

Key-words: Partial trisomy 10q - Chromosomal aberrations - Growth retardation - Multiple congenital anomalies - FISH studies - Genetic counseling.

INTRODUCTION

Chromosome rearrangements are an important cause of disturbed pre and post natal development. Trisomy and monosomy of most chromosomes are fatal during the prenatal development whereas, partial trisomies or monosomies are frequently encountered (21).

Partial trisomy of the distal third of the long arm of chromosome 10 is a well defined but rare syndrome. It was first described in 1965 by De Grouchy and Canet (11), then was further delineated by Yunis and Sanchez (44). Most described cases resulted from an unbalanced translocation, thus having a duplication-deficiency karyotype. Reported pure duplications are rare (24, 32, 39, 42).

The main clinical findings in partial trisomy 1 Oq are pre and post natal growth retardation, mental delay, hypotonia, microcephaly and dysmorphic facies in the form of flat face, high forehead, bow shaped eye brows and mouth, downward slanting of palpebral fissures, small eyes or blepharophimosis, low set malformed ears and micrognathia (38). Abnormalities of extremities, eyes, heart and kidneys were reported in the syndrome (10, 33, 42).

In this report we describe 2 Egyptian cases with partial 10q trisomy due to an unbalanced translocation of the distal part of 10q on the short arm of chromosome 7. The chromosomal abnormalities in both cases resulted from a parental balanced translocation involving chromosomes 10 and 7. The probands' phenotypes were correlated to the points of breakage and compared to previously reported cases with partial trisomy 10.

CASE REPORTS

CLINICAL FINDINGS

Case 1

The female proband was the first child of apparently healthy non-consanguineous 32-year-old mother and father after a history of 2 previous abortions. …

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