A male infant with Xq22.2q22.3 duplication containing PLP1 and MID2.

BACKGROUND: The Xq22.2 q23 is a complex genomic region which includes the genes MID2 and PLP1 associated with FG syndrome 5 and Pelizaeus-Merzbacher disease, respectively. There is limited information regarding the clinical outcomes observed in patients with deletions within this region. METHODS: We report on a male infant with intrauterine growth retardation (IUGR) who developed head titubation and spasticity during his postnatal hospital course. RESULTS: Chromosome microarray revealed a 6.7 Mb interstitial duplication of Xq22.2q22.3. Fluorescence in situ hybridization showed that the patient's mother also possessed the identical duplication in the Xq22.3q22.3 region. Among the 34 OMIM genes in this interval, the duplication of the PLP1 (OMIM# 300401) and MID2 (OMIM# 300204) appears to be the most significant contributors to the patient's clinical features. Mutations and duplications of PLP1 are associated with X-linked recessive Pelizaeus-Merzbacher disease (PMD). A single case of a Xq22.3 duplication including the MID2 has been reported in boy with features of FG syndrome. However, our patient's clinical features are not consistent with the FG syndrome phenotype. CONCLUSION: Our patient's clinical features appear to be influenced by the PLP1 duplication but the clinical effect of other dosage sensitive genes influencing brain development cannot be ruled out.

Utility of subtelomeric fluorescent DNA probes for detection of chromosome anomalies in 425 patients.

PURPOSE: A complete set of subtelomeric fluorescent DNA probes, except the acrocentric p-arms, was developed in 1996, was optimized in 1998, and is commercially available. These and other fluorescence in situ hybridization (FISH) probes have been used to detect anomalies of the subtelomere regions among groups of patients with idiopathic mental retardation (MR), developmental delay (DD), and/or nonspecific dysmorphic features (NDF), and individuals with multiple miscarriages (MM) who were karyotypically normal by standard G-banding techniques. METHODS: A total of 425 patients were analyzed, of whom 372 had idiopathic MR/DD/NDF and 53 were involved in MM. An effort was made to select individuals for this study who were either normal karyotypically or who had subtle chromosomal anomalies that were inconclusive by banded chromosome analysis, although this was not always possible. RESULTS: Anomalies involving the subtelomere regions were detected at a frequency of 6.8% in the MR/DD/NDF group. The cryptic or subtle anomalies are estimated to be about 3.4%. It was necessary to use M-FISH, chromosome, and locus specific FISH probes to clarify some of the abnormalities. No abnormalities were detected in the MM group. Deletion variants were present for 2qter, 7pter, and Xpter/Ypter subtelomeric regions ranging from <1 to 9.6%. CONCLUSIONS: The subtelomeric FISH probes are instrumental in the detection of subtelomeric anomalies in a significant proportion, although no more than 50% are subtle, of patients with idiopathic MR/DD/NDF. In some cases, however, it was necessary to use other FISH probes to clarify the nature of these abnormalities. No subtelomeric abnormalities were detected in our group of 53 MM patients, suggesting a relatively low frequency of occurrence in this patient population.