Unusual de novo Partial Trisomy 17p12p11.2 due to Unbalanced Insertion into 5p13.1 in a Severely Affected Boy

Abstract

Gain of copy numbers can be due to different chromosomal rearrangements such as direct or indirect duplications, translocations, small supernumerary marker chromosomes, or insertions. In a 3-year-old boy with dysmorphic features and developmental delay, chromosome analyses revealed a derivative chromosome 5. Microdissection and reverse fluorescence in situ hybridization identified the in 5p13.1 inserted part as 17p12-p11.2 material. Thus the patient suffered from a rare combination of genomic disorder, that is, Charcot-Marie-Tooth disease type 1A and Potocki-Lupski syndrome. Parental studies indicated that the abnormality was de novo in origin. As the question how this rearrangement arose cannot be answered conclusively, formal genetic counseling is warranted, which includes a discussion regarding the possibility of gonadal mosaicism. In conclusion, this case highlights that chromosome 17p is genetically relatively instable, and thus it can lead to rare chromosomal conditions.

Keywords: Charcot-Marie-Tooth disease type 1A; Potocki-Lupski syndrome; genotype-phenotype-correlation; insertion; molecular cytogenetics.

Fig. 1

(A) The patient is 2 years and 10 months old. (B) Both chromosomes 5 of the patient after high-resolution GTG banding; the derivative chromosome 5 (der(5)) presents with two unusual additional bands in 5p (arrow). (C) Results of reverse FISH after microdissection of the short arm of the der(5) from Fig. 1B . The obtained der-5p-probe gave signals on chromosomes of a normal male in 5p and 17p. (D) Here the reverse FISH result for chromosome 17 is shown in a larger magnification.