De novo isochromosome 18p in a female dysmorphic child

Minimally invasive endoscopic fenestration of a spinal arachnoid cyst in a child with tetrasomy 18p: illustrative case

BACKGROUND

Spinal arachnoid cysts (SAC) are rare, especially in children. Patients can be asymptomatic or present symptoms of spinal cord compression. In this latter case, surgery is indicated to relieve the compression. Different surgical techniques have been described to treat these cysts, endoscopic or endoscopy-assisted fenestration being the least invasive. Tetrasomy 18p describes the condition in which two copies of the short arms of chromosome 18 are present. It is an extremely rare pathology with a variable phenotype, including 100% of cases cognitive impairment and developmental delay. Different central nervous system (CNS) abnormalities have been found in these patients.

OBSERVATIONS

The authors describe the case of a 3-year-old boy with a tetrasomy 18p and a wide spinal arachnoid cyst that received an endoscope-assisted treatment with a significantly improved motor outcome.

LESSONS

Tetrasomy 18p is an extremely rare pathology and different CNS abnormalities have been described in association with, but to date spinal arachnoid cyst has never been reported. These children typically show global hypotonia and cognitive impairment. The authors recommend a thorough neurological assessment with cranio-spinal magnetic resonance imaging to rule out any possible malformation that could be improved by surgery.

Tetrasomy 18p Initially Misdiagnosed as Cerebral Palsy in an Adult Patient

Tetrasomy 18p is a rare genetic condition characterized by a supernumerary 18p isochromosome with two copies of the p arm of chromosome 18 causing patients to have an extra chromosome. Most cases are de novo; however, a few maternally inherited cases have been reported. The most commonly reported manifestations of this condition are developmental delay, cognitive impairments, muscle tone abnormalities, and dysmorphic facial features. This case details a new diagnosis of tetrasomy 18p in a 42-year-old adult who was initially diagnosed with cerebral palsy as a child. We compare the phenotypic traits of our patient with the ones reported in the literature.

Eye, Ocular Adnexa, and Facial Manifestations of Tetrasomy 18p

Tetrasomy 18p is often the result of an additional isochromosome for the short arm of chromosome 18. Although many organ systems are affected phenotypically, the ocular manifestations associated with tetrasomy 18p have not been well characterized in the literature. This case report presents the ocular and facial features associated with tetrasomy 18p in a 4-year-old Black girl, along with a review of clinical presentations previously reported in the literature. A systematic review of the literature in PubMed was conducted to summarize the reported eye, ocular adnexa, and distinctive facial features in individuals with confirmed tetrasomy 18p. Searching "Tetrasomy 18p" generated 65 article results, of which 28 articles had sufficient eye and facial descriptions. Including the patient in this report, 90 patients had confirmed tetrasomy 18p. The most common features noted in these 90 patients, with a roughly equal male-to-female ratio of impact (7:8), were as follows: microcephaly (57%), triangular facies (18%), anomalous palpebral fissures (31%), strabismus (48%), low-set ears (52%), hearing loss to some extent (16%), depressed or flat nasal bridge (18%), smooth philtrum (41%), thin upper lip (27%), and highly arched palate (21%). Additionally, many were noted to have feeding difficulties (28%), developmental delay (58%), and abnormal brain findings on imaging (20%). Muscle tone was abnormal in 23% of the patients. This report elucidates the reoccurring eye, ocular adnexa, and distinctive facial features associated with tetrasomy 18p. This knowledge may assist in timely diagnosis and encourage providers to use a multidisciplinary approach for the treatment of affected individuals. [J Pediatr Ophthalmol Strabismus. 2021;58(6):e44-e48.].

Tetrasomy 18p: case report and review of literature

Tetrasomy 18p syndrome (Online Mendelian Inheritance in Man 614290) is a very rare chromosomal disorder that is caused by the presence of isochromosome 18p, which is a supernumerary marker composed of two copies of the p arm of chromosome 18. Most tetrasomy 18p cases are de novo cases; however, familial cases have also been reported. It is characterized mainly by developmental delays, cognitive impairment, hypotonia, typical dysmorphic features, and other anomalies. Herein, we report de novo tetrasomy 18p in a 9-month-old boy with dysmorphic features, microcephaly, growth delay, hypotonia, and cerebellar and renal malformations. We compared our case with previously reported ones in the literature. Clinicians should consider tetrasomy 18p in any individual with dysmorphic features and cardiac, skeletal, and renal abnormalities. To the best of our knowledge, we report for the first time an association of this syndrome with partial agenesis of cerebellar vermis.

Tetrasomy 18p: report of cognitive and behavioral characteristics

Our purpose was to describe intellectual and behavioral characteristics of persons with tetrasomy 18p. This is a more detailed investigation into the cognitive and behavioral characteristics of our previously reported tetrasomy 18p cohort of 43 plus six additional participants. We evaluated the intellectual functioning using standard measures of cognitive ability, measures of executive functioning, adaptive and maladaptive behaviors. Intellectual abilities ranged from mild impairment/borderline normal to severe/profound impairment calling into question the assumption that severe cognitive limitation is always a feature of tetrasomy 18p. For persons with tetrasomy 18p with mild cognitive deficits, the main barriers to successful functioning stems from limited social and metacognitive skill development and behavior regulation problems rather than being solely determined by cognitive deficits alone.

Co-occurrence of mosaic supernumerary isochromosome 18p and intermittent 2q13 deletions in a child with multiple congenital anomalies

The present study deals with karyotpye-phenotype correlations in a six month old child with multiple congenital abnormalities. Cytogenetic analysis revealed mosaicism of a small metacentric supernumerary marker chromosome with a karyotype mos 47,XY+mar[34]/46,XY[31]. Cytogenetic microarray result showed three copies of chromosome 18p (15,400 kb in size). Moreover, 255 kbp intermittent deletion of chromosome 2q13 involving RGPD5, RGPD6, LIMS3, and LIMS3-LOC440895 was also observed. Correlating microarray data with the mosaic karyotype, the marker chromosome was identified as mosaic isochromosome 18p and was found to be 32,600 kbp in size. Baby resembled clinical characteristics of trisomy chromosome 18p, isochromosome 18p and trisomy chromosome 18. The present study suggested that deletion of evolutionarily conserved developmental genes (RGPD5, RGPD and LIMS3) in the 2q13 region might have contributed to more severity in phenotype as compared to so far such reported cases of 18p trisomy's, as these are involved in nuclear-cytoplasm trafficking, signaling for tissue patterning and differentiation.

A case report of prenatally diagnosed tetrasomy 18p

Tetrasomy 18p, one of the most commonly observed isochromosomes, consists of two copies of the p arms on chromosome 18[i(18p)]. It is known as a de novo occurrence of non-disjunction or centromeric mis-division during meiosis II in the vast majority of cases. It has a prevalence of 1/140,000-180,000 live births and affects both genders equally. A 28-year-old woman was referred at 33+2 weeks gestation to rule out fetal congenital heart disease. Her prenatal ultrasonography showed intrauterine growth retardation, cardiomegaly, and imperforate anus. Doppler ultrasonographic finding showed fetal anemia. Tetrasomy 18p was confirmed by conventional karyotyping and fluorescence in situ hybridization. Because of its very low prevalence rate, only several cases of tetrasomy 18p has been reported worldwide and it has not yet been reported in Korea before. Therefore, we report a case of prenatally diagnosed tetrasomy 18p.

Different conformation of two supernumerary 18p isochromosomes, one with a concomitant partial 18q trisomy

The presence of a supernumerary 18p isochromosome is a rare chromosomal abnormality that results in 18p tetrasomy. This is a report on the clinical, cytogenetic and molecular findings of 2 non-related patients with a supernumerary 18p isochromosome. Both patients present some features of the 18p tetrasomy syndrome (strabismus, low-set ears, long and narrow fingers and toes), but additional characteristics were also observed. Cytogenetic analysis, FISH, MLPA and SNP array techniques showed that one of the isochromosomes is symmetric and monocentric, while the other is asymmetric and dicentric, yet resulting in a similar tetrasomy of the 18pter-18p10 region, followed by a partial 18q11.2 trisomy, an unprecedented finding in the literature.

Ophthalmic manifestations of tetrasomy 18p

PURPOSE

To characterize ophthalmic findings in patients with tetrasomy 18p, a rare chromosomal anomaly that has been previously associated with strabismus.

METHODS

All subjects underwent a complete eye examination to screen for ocular pathology.

RESULTS

A total of 25 subjects (13 female) were examined after they were diagnosed with tetrasomy 18p. The average age of subjects was 8.2 years (range, 13 months to 22 years). Of the 25 subjects, 18 (72% of examined subjects, 42% of the cohort) showed evidence of strabismus; 16 had esotropia (8 uncategorized, 5 infantile, and 3 accommodative), 1 had esophoria, and 1 was diagnosed with intermittent exotropia.

CONCLUSIONS

The coincidence of esotropia with tetrasomy 18p indicates the need to routinely screen these patients for strabismus at the time of diagnosis.

Characterization of sSMC by FISH and molecular techniques

Small supernumerary marker chromosome (sSMC) is a structurally altered additional chromosome that may not be explicitly clarified by conventional karyotyping alone. About one third of sSMC carriers have abnormal phenotypes and its clinical correlation is difficult, especially in prenatal studies. The present study was aimed at characterizing 19 sSMC identified in 15 patients with dysmorphic features with or without multiple congenital anomalies, conspicuous family history, short stature and/or ambiguous genitalia. All the sSMC were primarily identified by routine cytogenetics studies (performed with banding techniques) from peripheral blood except in one patient, where amniotic fluid was used. All sSMCs were further characterized by array-CGH (using 44 K oligonucleotide probe) and/or fluorescence in situ hybridization (FISH) using multicolor banding (MCB), centromere specific multicolor FISH (cenM-FISH), subcentromere-specific multicolor FISH (subcenM-FISH), micro-dissection and/or reverse FISH. This report demonstrates the worth of advanced molecular (cyto)genetic techniques in characterizing sSMC, their utility in genotype-phenotype correlation and risk of clinical presentation.

Tetrasomy 18p: report of the molecular and clinical findings of 43 individuals

Thus far, the phenotype of tetrasomy 18p has been primarily delineated by published case series and reports. Findings reported in more than 25% of these cases include neonatal feeding problems, growth retardation, microcephaly, strabismus, muscle tone abnormalities, scoliosis/kyphosis, and variants on brain MRI. Developmental delays and cognitive impairment are universally present. The purpose of this study was to more fully describe tetrasomy 18p at both the genotypic and the phenotypic levels. Array CGH was performed on 43 samples from individuals with tetrasomy 18p diagnosed via routine karyotype. The medical records of 42 of these 43 individuals were reviewed. In order to gain additional phenotypic data, 31 individuals with tetrasomy 18p underwent a series of clinical evaluations at the Chromosome 18 Clinical Research Center. Results from the molecular analysis indicated that 42 of 43 samples analyzed had 4 copies of the entire p arm of chromosome 18; one individual was also trisomic for a section of proximal 18q. The results of the medical records review and clinical evaluations expand the phenotypic description of tetrasomy 18p to include neonatal jaundice and respiratory distress; recurrent otitis media; hearing loss; seizures; refractive errors; constipation and gastroesophageal reflux; cryptorchidism; heart defects; and foot anomalies. Additional findings identified in a small number of individuals include hernias, myelomeningocele, kidney defects, short stature, and failure to respond to growth hormone stimulation testing. Additionally, a profile of dysmorphic features is described. Lastly, a series of clinical evaluations to be considered for individuals with tetrasomy 18p is suggested.