Array CGH on unstimulated blood does not detect all cases of Pallister–Killian syndrome: A skin biopsy should remain the diagnostic gold standard

Abstract

A child whose features are consistent with Pallister-Killian syndrome (PKS) did not have detectable tetrasomy 12p due to an additional isochromosome 12p in an unstimulated blood specimen by interphase FISH or array CGH analysis. The diagnosis of PKS was made through these methods solely in a skin biopsy specimen. To determine the sensitivity of our array CGH platform to tetrasomy 12p mosaicism, dilutions of DNA from both the child's skin fibroblasts and a PKS cell line were analyzed. Tetrasomy 12p at 10% mosaicism was identifiable but 5% was below the limit of detection. This result suggests through extrapolation that the tetrasomy 12p is present in <10% of cells in our patient's blood, confirming the tissue-limited mosaicism of PKS. Multiple recent studies show that array CGH provides greater sensitivity than chromosome analysis to detect mosaic abnormalities including that of tetrasomy 12p in blood specimens. However, our case demonstrates that the biology of PKS precludes the exclusive use of array CGH on blood for diagnosis. A tissue sample should continue to be the diagnostic gold standard for PKS.

Interphase fluorescence in situ hybridization characterization of mosaicism using uncultured amniocytes and cultured stimulated cord blood lymphocytes in prenatally detected Pallister–Killian syndrome

“…Cheung et al [15], Powis et al [16], and Theisen et al [17] later demonstrated the usefulness of aCGH using peripheral blood DNA to detect chromosomal mosaicism including PKS not revealed by conventional blood cytogenetics. However, aCGH on unstimulated blood has been shown to fail to detect all cases of PKS because of the limitation of aCGH to detect the cases with tetrasomy 12p at < 10% of the mosaic level [18]. Either a skin biopsy [18] or a buccal smear analysis [19] has been suggested as a diagnostic gold standard for PKS in postnatal cases.…”

“…However, aCGH on unstimulated blood has been shown to fail to detect all cases of PKS because of the limitation of aCGH to detect the cases with tetrasomy 12p at < 10% of the mosaic level [18]. Either a skin biopsy [18] or a buccal smear analysis [19] has been suggested as a diagnostic gold standard for PKS in postnatal cases.…”

Using Array-Based Comparative Genomic Hybridization to Diagnose Pallister-Killian Syndrome

“…However, array CGH of unstimulated peripheral lymphocytes has failed to detect all cases of PKS because it can detect mosaic abnormal cells at prevalence not lower than 10-20% [1011]. Analysis of skin fibroblasts [19] or buccal smears [20] has been proposed as a diagnostic gold standard, but this notion is still controversial. Hodge et al [19] proposed that a skin biopsy sample should continue to be the diagnostic gold standard for PKS because of the variable and insufficient quality of buccal smears.…”

“…Analysis of skin fibroblasts [19] or buccal smears [20] has been proposed as a diagnostic gold standard, but this notion is still controversial. Hodge et al [19] proposed that a skin biopsy sample should continue to be the diagnostic gold standard for PKS because of the variable and insufficient quality of buccal smears. Nonetheless, Cobben et al [20] showed that in patients with suspected PKS, array CGH or FISH analysis of buccal smear cells seems to be the first diagnostic choice because these two methods are reliable, rapid, and noninvasive.…”

Mosaic chromosomal aneuploidy detection by sequencing (MAD-seq)

“…The nature of the developmental event is such that it may only affect an anatomically-restricted group of cells in the body, whereas routine genetic testing is almost always performed upon DNA from peripheral blood leukocytes, looking for constitutive, germ line mutations. Blood, in particular when cultured, is especially poor as a choice of cells for detection of mosaic aneuploidy (exemplified by the failure to detect tetrasomy 12p in Pallister-Killian syndrome [12][13][14], with blood-derived lymphoblastoid cell lines (LCLs) likely to be even worse, given their striking oligoclonality. 15 Current large-scale studies of human phenotypes, mostly based on blood or LCL DNA, are therefore unlikely to be optimally sensitive for detection of the presence of mosaic chromosomal aneuploidy.…”