We present 4 recently diagnosed cases of inverted tandem duplication with involvement of the respective terminal band. Based on these 4 cases and review of the literature, the term "inverted terminal duplication" is proposed to designate specifically the type of inverted tandem duplication which involves the terminal band. A modification of the previous hypothesis of mechanism of origin is advanced. It is speculated further that a telomeric deletion of a meiotic chromosome followed by a U-type reunion of the chromatids, considered to be the first steps of the proposed mechanism of origin, may not be a rare gonadal event.
We present a patient with oculocerebrocutaneous syndrome. The boy shows only mild psychomotor delay in spite of rather severe appearing anomalies of the central nervous system. A primarily unilateral involvement of this syndrome is emphasized. A postzygotic/somatic mutation resulting in a mosaic state might account for the primarily ectodermal involvement, the unilateral predominance, and the sporadic nature of this syndrome. An alternative hypothesis of an environmental factor might also explain the clinical manifestations of the syndrome.
A patient with Prader‐Willi syndrome showed an elongated proximal 15q, and thus was initially considered to be negative for a proximal 15q deletion. However, repeated high resolution chromosome study demonstrating the DNA‐replication banding patterns revealed an obvious deletion/deficiency of the 15q12 equivalent band on that elongated chromosome 15. This deletion was further verified by comparison with the parental chromosomes 15 and the deleted chromosome 15 was of paternal origin. The elongation was due to a long variant of 15q11.2 band, which has previously been shown to be polymorphic/variable. This variable proximal 15q site could potentially mask a deletion if it is too long, or mimic a deletion if it is too short. The use of the DNA‐replication banding technique instead of the more widely used trypsin banding technique could alleviate this possible pitfall.
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