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Intellectual Disability Related to De Novo Germline Loss of the Distal End of the P-Arm of Chromosome 17: A Case Report
Hypothesis/Purpose: In this report we present a case of a 20-year-old female with congenital intellectual disability, stunted growth, and hypothyroidism. Competitive genetic hybridization (CHG) revealed a loss of 17p13.3, and the deletion was not present in either parent. This deletion has not previously been characterized, but mutations on the p-arm of chromosome 17 are responsible for Miller-Dieker Syndrome and Isolated Lissencephaly Sequence, both of which share symptoms in common with the patient.
Methods: Peripheral mononuclear cells (PBMCs) were used for karyotyping and competitive genetic hybridization (CHG). Bioinformatic analysis was carried out using the Genome Data Viewer (ncbi.nlm.nih.gov/genome/gdv).
Results: Karyotype was found to be normal, but CGH revealed a deletion of the tail end of the p-arm of chromosome 17, 17p13.3. At least 134 genes are present in this genomic location, and 35 of them are uncharacterized. Both Miller-Dieker Syndrome (MDS) and Isolated Lissencephaly Sequence (ILS) are characterized by a smooth cerebral cortex and intellectual disability, but the patient’s symptoms more closely mirror MDS because muscle tone was normal. The patient was significantly shorter than peers, but growth hormone therapy over the course of several years allowed the patient to reach a normal height, albeit shorter than her siblings and parents. The list of genes deleted will be investigated to determine if a single gene is likely responsible for the phenotype.
Conclusions: Here we present a patient with intellectual disability and a previously uncharacterized deletion on chromosome 17. Similar, though not identical conditions have been previously reported, but not well characterized indicating that the present patient could possibly have one of these conditions. Further directions include investigation of the deleted genes to determine a probable cause for the symptoms exhibited.