Prenatal detection of Peters plus-like syndrome

Peters plus syndrome is a rare congenital disorder that includes ocular anterior segment defects of the classic Peter’s anomaly, and is mostly associated with craniofacial and skeletal defects. A 21-week fetus was referred for further evaluation due to a suspicion of fetal hydrocephalus. An ultrasound examination revealed hyperechogenic lenses, microphthalmia, hypotelorism, retrognathia, mild ventriculomegaly, absence of the cavum septum pellucidum, and short stature. Amniocentesis and further microarray analysis revealed normal chromosomal copy numbers including the gene B3GALTL. In utero mort fetalis occurred at the 23rd gestational week. Ultrasound and fetal autopsy findings were suggestive of Peters plus syndrome, but the absence of the B3GALTL gene mutation made the diagnosis Peters plus-like syndrome. Obstetricians should consider Peters plus-like syndrome with prenatal detection of ocular anomalies along with craniofacial and skeletal anomalies with the absence of B3GALTL gene mutation.


Introduction
Peters' anomaly is a rare congenital ocular anomaly caused by defective dysgenesis and cleavage of the anterior chamber of the eye causing central corneal opacity (leukoma), absence of the posterior corneal stroma and Descemet membrane, and a variable degree of iris and lenticular attachments to the central aspect of the posterior cornea (1) . Peters plus syndrome, previously known as Krause-Kivlin syndrome or Peters' anomaly with short-limb dwarfism (OMIM ≠ 261540), is an autosomal-recessive inherited congenital disorder caused by a mutation in the B3GALTL gene on chromosome 13q12.3. Peters plus syndrome is a rare anomaly with unknown incidence, with equal sex ratio, and a high incidence of consanguinity. Just over 70 cases have been reported in the postnatal period and 8 cases in the prenatal period (2)(3)(4)(5)(6) . The classic triad of Peters plus syndrome includes anterior segment defects (100%), short stature (100%), and brachydactyly (95%) (7) . There are also Peters plus-like syndromes, which did not carry a mutation in the B3GALTL gene, but have similar anomalies to the classic Peters-plus syndrome (8) . Herein, we report the prenatal diagnosis of Peters plus-like syndrome in a Turkish family without the B3GALTL gene mutation.

Case Report
A 23-year-old woman, gravida1 partus 0, was referred to our clinic at the 21 st week of her pregnancy due to the suspicion of fetal hydrocephalus. The fetal biometry scan showed appropriate biometric measurements, but long bone measurements, including femur, fibula, radius, and ulna were one week shorter than the expected gestational age. The detailed scan showed a female fetus with moderate ventriculomegaly, absence of the cavum septum pellucidum, a dilated third ventricle (Figure 1), echogenic lenses ( Figure 2), retrognathia (inferior mandibular angle <50°), hypotelorism (binocular distance at 5 th percentile and inter-ocular distance at 50 th percentile), and microphthalmia (ocular diameter <5 th percentile) ( Figure 2

Discussion
If typical ocular anomalies of Peters' anomaly accompany with additional malformations, this situation is referred to as Peters plus syndrome. Peters plus syndrome was initially understood as a causally heterogeneous morphologic entity (2,3) . It is now a well-defined syndromic disorder, being confined to a narrower spectrum of accompanying malformations and being related to homozygous or compound heterozygous B3GALTL mutations (7) . However, other syndromes with a Peter's anomaly do not fulfill the criteria of Peters plus syndrome.
The clinical features of Peters plus syndrome includes a prominent forehead, narrow palpebral fissures, a long philtrum, cupid's bow upper lips, cleft lip and palate, preauricular ribs, micrognathia, a broad neck, cataracts and glaucoma, short limbs, brachydactyly, clinodactyly, microcephaly, brain atrophy, agenesis of the corpus callosum, and variable developmental delay and intellectual disability. Some of these features may be present prenatally or at birth, and some may occur at later ages (2) . In contrast to other prenatally detected Peters plus syndrome cases, our case did not show a B3GALTL gene mutation. In prenatally detected cases of Peters plus syndrome, including our case, no B3GALTL gene mutation has been reported to date (5,9) . There may be some explanations for this situation; these cases may be a variant or a phenotypic overlap of Peters plus syndrome (8) or these cases may carry a distinct mutation, which needs further investigation. We also analyzed various mutations in genes that were shown to be linked to the ocular anomaly of Peters' syndrome or involved in eye development (PAX6, PITX2, PITX3, CYP1B1, FKHL7), and no mutations were observed in these genes either. In this situation, our case is more suitable for defining as Peters plus-like syndrome. Prenatal detection of Peters plus syndrome and like syndromes require a handful of dedicated physicians, including obstetricians, ophthalmologists, genetic specialists, and pathologists. In particular, obstetricians and ultrasonographers should pay attention to the eye, and if ocular anomalies are suspected, craniofacial and skeletal system and fetal growth monitoring should be remembered for the prenatal detection of Peters plus syndrome. In the differential diagnosis of Peters plus syndrome, similar syndromes such as SHORT, Abbruzo-Erickson, GMS, Weill-Marchesani, Michels, Rieger, Walker-Warburg, Cornelia de Lange, Robinow, and fetal alcohol syndrome can be detected according to Orphanet data (http:77www.orpha.net). Herein, we report a case of Peters plus-like syndrome that was prenatally detected in a patient from Turkey with no family history. The diagnosis was made solely through prenatal ultrasound despite normal fetal chromosomes and no mutation in the B3GALTL gene in this sporadic case. As a result, in cases of fetal anterior segment defects, obstetricians should remember Peter's anomaly, Peters plus syndrome, and Peters plus-like syndrome, and they should also scan for other accompanying features of these diseases, and perform prenatal invasive tests, including specific gene mutations.

Ethics
Informed Consent: Informed consent acquired from the patient to publish this case report. Peer-review: Externally peer-reviewed.