Prenatal diagnosis and neonatal phenotype of a de novo microdeletion of 17p11.2p12 associated with Smith–Magenis syndrome and external genital defects

Smith–Magenis syndrome (SMS, OMIM: 182290) is a multiple congenital anomalies and intellectual disability syndrome due to a 3.45 Mb microdeletion involving 17p11.2 and is estimated to occur about one in 25,000 births. Up to now, the ultrasound findings of the foetus with SMS and their external genital defects in patients are rarely reported. This case indicates that foetus with SMS may present polyhydramnios and ventriculomegaly in the second trimester. The newborn male patient had an abnormal phenotype in which he has micropenis and his anus is close to the perineal body. The identification of this case may further expand the phenotypic spectrum of this genetic disorder.

Duplication 17p11.2 (Potocki-Lupski Syndrome) in a child with developmental delay

Potocki-Lupski syndrome (PTLS), also known as duplication 17p11.2 syndrome, trisomy 17p11.2 or dup(17)(p11.2p11.2) syndrome, is a developmental disorder and a rare contiguous gene syndrome affecting 1 in 20,000 live births. Among the key features of such patients are autism spectrum disorder, learning disabilities, developmental delay, attention-deficit disorder, infantile hypotonia and cardiovascular abnormalities. Previous studies using microarray identified variations in the size and extent of the duplicated region of chromosome 17p11.2. However, there are a few genes which are considered as candidates for PTLS which include RAI1, SREBF1, DRG2, LLGL1, SHMT1 and ZFP179. In this report, we investigated a case of a 3-year-old girl who has developmental delay. Her chromosome analysis showed a normal karyotype (46,XX). Analysis using array CGH (4X44 K, Agilent USA) identified an ~4.2 Mb de novo duplication in chromosome 17p11.2. The result was confirmed by fluorescence in situ hybridization (FISH) using probes in the critical PTLS region. This report demonstrates the importance of microarray and FISH in the diagnosis of PTLS.

Reciprocal Deletion and Duplication of 17p11.2-11.2: Korean Patients with Smith-Magenis Syndrome and Potocki-Lupski Syndrome

Deletion and duplication of the -3.7-Mb region in 17p11.2 result in two reciprocal syndrome, Smith-Magenis syndrome and Potocki-Lupski syndrome. Smith-Magenis syndrome is a well-known developmental disorder. Potocki-Lupski syndrome has recently been recognized as a microduplication syndrome that is a reciprocal disease of Smith-Magenis syndrome. In this paper, we report on the clinical and cytogenetic features of two Korean patients with Smith-Magenis syndrome and Potocki-Lupski syndrome. Patient 1 (Smith-Magenis syndrome) was a 2.9-yr-old boy who showed mild dysmorphic features, aggressive behavioral problems, and developmental delay. Patient 2 (Potocki-Lupski syndrome), a 17-yr-old boy, had only intellectual disabilities and language developmental delay. We used array comparative genomic hybridization (array CGH) and found a 2.6 Mb-sized deletion and a reciprocal 2.1 Mb-sized duplication involving the 17p11.2. These regions overlapped in a 2.1 Mb size containing 11 common genes, including RAI1 and SREBF.

Diagnosis of Neuropathies for CMT1A and HNPP Using the Microsatellite Multiplex PCR System

BACKGROUND: Tandem duplication of chromosome 17p11.2-p12 including peripheral myelin protein 22 (PMP22) gene is the most frequent cause of Charcot-Marie-Tooth 1A (CMT1A). Patients carrying one extra copy of PMP22 develop CMT1A, whereas the deletion of the 17p11.2-p12 region causes hereditary neuropathy with the liability to pressure palsies (HNPP). In the present study, we established the genotyping methods of 6 microsatellite markers (D17S921, D17S9B, D17S9A, D17S4A, D17S918 and D17S122) within the 17p11.2-p12 regions by the hexaplex PCR for the genetic diagnosis of CMT1A duplication and HNPP deletion. METHODS: We established polymorphic behavior and genotyping methods of 6 microsatellite markers (D17S921, D17S9B, D17S9A, D17S4A, D17S918 and D17S122) within the duplication region. The 6 markers were amplified by hexaplex PCR reaction and analyzed by an automatic sequencing analyzer and genotyper program. RESULTS: The genotype distributions of all markers were not significantly deviated from the Hardy-Weinberg equilibrium (P>or=0.05). When comparing the control group and CMT1A, HNPP patients group by the distribution of allele, there is no significant difference in the 5 locus except in the 1 locus (D17S921) among HNPP patients. The specificity was more than 99.9%. The sensitivity of each CMT1 and HNPP was 56.3% (40/71 pedigrees) and 72.1% (31/43 HNPP pedigrees), respectively. CONCLUSIONS: The error rate for the system may be less than 0.001. According to this study, it is possible to have rapid and exact genetic diagnosis of both CMT1A and HNPP, which may be helpful for the development of personalized therapy according to genetic defects.

Clinical, Electrophysiological and Pathological Characteristics in Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) with Chromosome 17p11.2-p12 Deletion

BACKGROUND: Hereditary neuropathy with liability to pressure palsies (HNPP) is a peripheral nerve disorder characterized by autosomal dominant inheritance, recurrent pressure palsies, reduced motor and sensory conduction velocities and sausage-like swellings (tomacula) of myelin sheaths in nerve biopsy. A 1.5-Mb deletion in chromosome 17p11.2- p12 is present in the majority but not all cases of HNPP. The aim of the present study was to evaluate the clinical, electrophysiological and morphological aspects of HNPP patients associated with chromosome 17p11.2-p12 deletion. METHODS: To detect the presence of the deletion, the DNA of the patients was analyzed with pVAW409R3 (D17S122). An electrophysiological study was done in all patients. Sural nerve biopsy with teasing was done in three patients. RESULTS: DNA analysis and electrophysiological tests revealed the deletion in 8 families and 16 patients. Nerve conduction studies demonstrated diffuse mild to moderate slowing of nerve conduction velocities especially worse over the common entrapment sites, regardless of clinical manifestations. The long duration of compound muscle and nerve action potentials without conduction blocks or dispersion is characteristic of patients with HNPP. The tomacula of myelin sheaths was found on sural nerve teasing. CONCLUSIONS: We report the clinical, electrophysiological and morphological aspects of the Korean HNPP patients associated with chromosome 17p11.2-p12 deletion. (J Korean Neurol Assoc 19(3):251~259, 2001)

Intraoperative Electrophysiological Monitoring during Microvascular Decompression for Hemifacial Spasm and Surgical Outcome

BACKGROUND: Hereditary neuropathy with liability to pressure palsies (HNPP) is a peripheral nerve disorder characterized by autosomal dominant inheritance, recurrent pressure palsies, reduced motor and sensory conduction velocities and sausage-like swellings (tomacula) of myelin sheaths in nerve biopsy. A 1.5-Mb deletion in chromosome 17p11.2- p12 is present in the majority but not all cases of HNPP. The aim of the present study was to evaluate the clinical, electrophysiological and morphological aspects of HNPP patients associated with chromosome 17p11.2-p12 deletion. METHODS: To detect the presence of the deletion, the DNA of the patients was analyzed with pVAW409R3 (D17S122). An electrophysiological study was done in all patients. Sural nerve biopsy with teasing was done in three patients. RESULTS: DNA analysis and electrophysiological tests revealed the deletion in 8 families and 16 patients. Nerve conduction studies demonstrated diffuse mild to moderate slowing of nerve conduction velocities especially worse over the common entrapment sites, regardless of clinical manifestations. The long duration of compound muscle and nerve action potentials without conduction blocks or dispersion is characteristic of patients with HNPP. The tomacula of myelin sheaths was found on sural nerve teasing. CONCLUSIONS: We report the clinical, electrophysiological and morphological aspects of the Korean HNPP patients associated with chromosome 17p11.2-p12 deletion. (J Korean Neurol Assoc 19(3):251~259, 2001)