Discussion
Agenesis of the corpus callosum is one of the most frequently found
structural brain abnormalities with several recognized syndromic
correlations and genetic disorders, with an incidence between 0.03 to
0.7% [16]. Polydactyly and agenesis of the corpus callosum are
characteristics of acrocallosal syndrome (ACLS). Despite the high
incidence of hand and foot polydactyly, preaxial polydactyly of the foot
is expected to occur in only 0.4 cases per 10,000 Europeans [17].
Preaxial polydactyly of the foot is related with other congenital
anomalies and syndromes, such as craniosynostosis, renal malformations,
and also corpus callosum agenesis in ACLS as seen in our patient. ACLS
is an extremely rare developmental condition and only roughly forty
cases have been reported globally to date [18].
According to the criteria established by Courtens et al in 1997, the
diagnosis of ACLS can be made if at least three of the following four
criteria are present: 1) Minor craniofacial abnormalities 2) Moderate to
severe mental retardation with hypotonia 3) Polydactyly 4) Total or
partial absence of the corpus callosum [19]. Polydactyly and
agenesis of the corpus callosum and widening of the anterior fontanelle
were observable in our patient, but despite the structural abnormalities
of the brain, the patient’s neurological exams were normal. Due to the
child’s young age, it is currently impossible to form a definitive
assessment on his mental development.
The cardiac results are comparable to prior reports of congenital heart
diseases found in two other cases. In the report by Casamassima et al.,
the child diagnosed with ACLS displayed tetralogy of Fallot on
echocardiogram and Wolff-Parkinson-White Type B on electrocardiogram
[20]. In Singhal et al. report, the echocardiography of the patient
with ACLS indicated a small secundum type ASD with moderate tricuspid
regurgitation and dextro positioning of the heart. [14]. Considering
that ASD was detected by echocardiography in the present study, it is
possible that cardiac abnormalities are among the symptoms of this
syndrome.
Acrocallosal syndrome, Joubert syndrome, and hydrolethalus fetal
syndrome are all caused by a missense mutation in KIF7(15q26.1), a
modulator of ciliary Hedgehog signaling [21]. Due to the autosomal
recessive inheritance pattern of ACLS, the recurrence risk is 25%,
making genetic counseling essential. In our case, the genetic test had
revealed that the patient’s parents were healthy. According to the
studies, although autosomal recessive inheritance has been proposed,
ACLS often tends to happen sporadically [22]. It was also noteworthy
that the patient’s mother worked as a hairdresser and had been exposed
to chemicals during pregnancy. In a study by Rylander et al., it was
determined that a greater proportion of children born to hairdressers
suffered major malformations (2.8% vs 2.1%) [23]. However, in
previous studies, mostly oral clefts have been linked to mother’s
occupation as a hairdresser [24]. On the other hand, laboratory
research on mice have demonstrated that exposure to cosmetics-related
chemicals including toluene, significantly raises an index of poor
perinatal outcome, comprising morphological and marginal
neurodevelopmental malformations and newborn mortality [25]. These
studies imply that the mother’s exposure to cosmetic-related substances
may be a possible cause of the neonate’s abnormalities.