INTRODUCTION
Renal coloboma syndrome (RCS) is an autosomal dominant disorder with
high penetrance and variable expressivity.1 RCS is
primarily characterized by renal dysplasia and abnormalities of the
optic nerve.1,2
Although there is no formal diagnostic criteria for RCS, it is thought
to be associated with a heterozygous pathogenic variant inPAX2 .1 50% of patients with clinical findings
suggestive of RCS (e.g. renal and ocular malformations) have a mutation
in the PAX2 gene.2 As a result of improved
access to molecular genetic testing, more individuals with PAX2mutations have been identified with a wide phenotypic
variability.2
Renal and ocular findings are reported in 92% and 72% of affected
individuals respectively.1 Abnormalities in kidney
structure and function are among the most frequent findings in
individuals with PAX2 mutations, which include: renal dysplasia,
multicystic dysplastic kidney and end-stage renal disease. Primary
ocular findings involve optic nerve dysplasia that ranges from severe to
mild.1,2
Reports of prenatal RCS findings have been limited, highlighting the
importance of intrafamilial monitoring among affected individuals. Once
a PAX2 pathogenic variant has been identified in a family,
prenatal genetic testing for the familial variant becomes possible, in
addition to screening through ultrasound (US), to detect any renal
malformations and assess amniotic fluid levels.1 To
date, only six case reports and one large series have been published on
prenatal RCS findings.3-8 Of the six case reports,
four involved terminated pregnancies as a result of prenatal US findings
of fetal renal dysplasia, and/or oligohydramnios.3-5Common findings among all case reports include bilateral fetal renal
hypoplasia and observed bilateral optic disc colobomas postnatally. Upon
genetic testing, there is considerable variability in the PAX2gene variants, with most case reports having a de novo
mutation.4,5,7,8 Notably, one case report presents a
male with moderate-severe oligohydramnios for which an amnio-infusion of
250 ml of normal saline was performed. The remainder of the pregnancy
was monitored with serial US examinations, leading to a live birth
following that intervention.3
Bower et al reported one of the biggest RCS prenatal case series
that added 13 prenatal cases to the literature.9 Six
of the 13 fetuses were terminated given prenatal findings of renal
hypoplasia, in addition to severe oligohydramnios. All six cases had
parents confirmed with a pathogenic PAX2 variant. The other seven
surviving cases had de novo mutations. Five out of the seven had normal
amniotic fluid levels, while the other two had mild oligohydramnios, in
addition to a renal hypoplasia or dysplasia. None of the 13 cases
reviewed had self-resolving oligohydramnios.
We further add to the literature a report of mother and her newborn with
RCS, both presenting prenatally with self-resolving severe
oligohydramnios as an early prenatal finding.