Mosaic chromosome 12 abnormality in a child with significant growth and developmental delay
We describe a child who presented with failure to thrive, microcephaly and developmental delay. She was delivered at 34 weeks weighing 1.3 kg. She had no major physical problems except for laryngomalacia. On review at aged 6 years, she had significant global developmental delay. She had marked microcephaly and significant short stature. She had some mildly dysmorphic features. Previous investigations had demonstrated no abnormality. In view of her phenotype, a detailed karyotype and subtelomere chromosome analysis were requested.
Chromosome analysis showed the presence of an abnormal banding pattern on the short arm of one chromosome 12 in approximately 40% of banded metaphases. Interphase FISH revealed a deletion of 12PTEL on the abnormal chromosome. Whole chromosome paint showed the abnormal chromosome was comprised of chromosome 12 material. There was a duplication of TEL on the p arm of the abnormal 12.
A possible explanation for these findings is a partial duplication of 12p, possibly with deletion and/or inversion of some material.
M-Band studies are in progress in an attempt to further elucidate the karyotype and the phenotype will be discussed in more detail.