Infantile Hypertrophic Pyloric Stenosis in A Pair of Preterm Monozygotic Male Twins: A Report of Two Cases
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Case Report Frontiers in Medical Case Reports, ISSN: 2582-8142
DOI: http://dx.doi.org/10.47746/FMCR.2022.3206
Infantile Hypertrophic Pyloric Stenosis in A Pair of Preterm Monozygotic
Male Twins: A Report of Two Cases
Laith A. Ayasa1 | Majd A. Abu Alrob1 | Ayman A. Salman2 | Ahmed H. Aliwisat3* | Ahmad M. Shaltaf3*
*Correspondence: Ahmed Hasan Aliwisat and Ahmad Mustafa Shaltaf
Address: 1College of Medicine, Al-Quds Medical School, Jerusalem, Palestine; 2Department of Neurosurgery, Al-Makassed Islamic
Charitable Hospital, Jerusalem, Palestine; 3Department of Pediatric Surgery, Al-Makassed Islamic Charitable Hospital, Jerusalem,
Palestine
e-mail : ahmadsat2012@gmail.com; dr_shaltaf@yahoo.com
Received: 28 March 2022; Accepted: 11 April 2022
Copyright: © 2022 Ayasa LA. This is an open-access article distributed under the terms of the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided that the original work is
properly cited.
ABSTRACT
We present a case of preterm monozygotic male twins that had similar clinical presentation and were diagnosed
with Infantile Hypertrophic Pyloric Stenosis (IHPS). They both were treated with open pyloromyotomy with no
reported complications. This report aims to add clinical evidence to further highlight the genetic contribution in
the pathophysiology of IHPS, a disease with a noteworthy clinical significance, given its frequency in the neonatal
period.
Keywords: Pyloric Stenosis, Monozygotic, Genetic, Pyloromyotomy, Prematurity
Introduction
Infantile Hypertrophic Pyloric Stenosis (IHPS) is a surgical condition prevalent in infants with a
rate of 1.8 – 3 per 1000 live births varying from region to region, and is characterized by thickening of the
pylorus muscle, causing obstruction of the gastric outlet (Krogh et al., 2010). It is considered the most
common cause of surgery in infants1. IHPS is more common in males (5:1) and in preterm infants as well
(Krogh et al., 2012). The cause of IHPS is not clear (Peeters et al., 2012), but it is believed to be
multifactorial. Some of the reported risk factors include; prematurity, cesarean delivery, and maternal
smoking (Svenningsson et al., 2014). Although there seems to be a hereditary factor involved in the
prevalence of IHPS (Krogh et al., 2010), a number of genetic studies explored and tried to determine an
established and specific genetic associations but none of them were replicable in subsequent trials
(Peeters et al., 2012). In this report, we present a case of monozygotic male twins that were diagnosed
with IHPS, thereby providing more evidence to support the genetic factor’s contribution to the physiology
of IHPS.
Cite this article: Ayasa LA, et al. Infantile Hypertrophic Pyloric Stenosis in A Pair of Preterm Monozygotic Male Twins: 1
A Report of Two Cases. Front Med Case Rep 2022; 3(2): 1-05.Case Report Ayasa LA et al., 2022; 3(2): 1-05
DOI: http://dx.doi.org/10.47746/FMCR.2022.3206
Case Presentation
A pair of monozygotic male twins presented to our hospital at 40 days of age with non-bilious
vomiting for 3 days.
Both were doing well until 3 days prior to presentation, when acute, projectile, and non-bilious
vomiting started. It was exacerbated by feeding and relieved following emesis. There was no greenish or
bloody material. There was no fever, poor feeding, hypoactivity, diarrhea, constipation, abdominal
distention, runny nose, cough, or ill contacts.
There was no history of any maternal issues during pregnancy. The patients were born to a
Gravida 3, Para 3 woman at the gestational age of 34 weeks via cesarean section out of a consanguineous
marriage (parents are first cousins). Twin 1’s birth weight was 1500 g; his weight on admission was 2550
g. Twin 2’s birth weight was 1700 g; his weight on admission was 2800 g. Both were admitted to the
neonatal intensive care unit (NICU) for 20 days due to their premature birth. Their vaccination status was
up to date for age according to the Palestinian Ministry of Health vaccination program with no reported
side effects. There were no known food or drug allergies. Both patients were maintained breast and
formula fed. They have 2 healthy siblings. There is no history of Hypertrophic Pyloric Stenosis in the
family from neither the paternal nor maternal side.
Investigations
Table 1 provides a summary of the laboratory values obtained for the pair of twins. On admission,
Twin 1’s arterial blood gases (ABGs) showed metabolic alkalosis; pH: 7.51, CO2:37 mmol/l, HCO3: 29.8
mmol/l. Twin 2 ABGs were within the normal range; pH: 7.35, CO2:38.8 mmol/l, HCO3: 22.2 mmol/l. The
Electrolyte values for Twin 1; Na: 135 mEq/l, K: 4.26 mEq/l, Cl: 93.1 mEq/l. The electrolytes for twin 2
were Na: 135 mEq/l, K: 4.98 mEq/l, Cl: 102 mEq/l. Both of them had indirect hyperbilirubinemia; The
total serum Bilirubin values were 8 mg/dl (Direct Bilirubin: 0.68 mg/dl) and 6.45 mg/dl (Direct Bilirubin:
0.34 mg/dl) for twin 1 and twin 2, respectively. Initial inflammatory markers were within normal range
for both.
Table 1: Summary of the arterial blood gases values and the electrolyte values for twin 1 and twin 2 of the monozygotic
twins diagnosed to have IHPS.
pH CO2 HCO3 Na K Cl
Twin 1 7.51 37 mmol/l 29.8 mmol/l 135 mEq/l 4.26 mEq/l 93.1 mEq/l
Twin 2 7.35 38.8 mmol/l 22.2 mmol/l 135 mEq/ 4.98 mEq/l 102 mEq/l
An abdominal ultrasound was performed for both, and it revealed an enlarged pylorus with the
Front Med Case Rep, ISSN: 2582-8142 https://www.jmedicalcasereports.org/ 2Case Report Ayasa LA et al., 2022; 3(2): 1-05
DOI: http://dx.doi.org/10.47746/FMCR.2022.3206
following measurements (Table 2):
Twin1; The length was 22 mm (Upper limit: 17 mm). Thickness was 5 mm (Upper limit: 3 mm)
with “antral nipple” sign.
Twin 2; The length was 19 mm (Upper limit: 17 mm). Thickness was 4.8 mm (Upper limit: 3 mm).
Table 2: Measurements of the pylorus muscle parameters for twin 1 and twin 2 of the monozygotic twins diagnosed to
have IHPS.
Pylorus Muscle Length Pylorus Muscle Thickness
Twin 1 22 mm 5 mm
Twin 2 19 mm 4.8 mm
The investigation confirmed the diagnosis of Infantile Hypertrophic Pyloric Stenosis.
Treatment
Diagnosis of IHPS was confirmed after investigations. Both patients were kept nothing-by-mouth
(NPO), on free drainage, with maintenance-adjusted intravenous fluids. They were scheduled for a Trans-
umbilical Pyloromyotomy (Bianchi Incision) (Fig. 1).
Twin 1 ABGs were not improving prior to the scheduled operation, so it was postponed to the
following day. Twin 2 underwent a successful operation as planned.
Both were breastfed on the first post-operation day and were discharged from the hospital on the
fourth post-operation day.
On follow-up clinic visits, growth parameters and developmental milestones were age
appropriate for both patients.
Figure 1: Intra-operative illustration of trans-umbilical pyloromyotomy in twin 1 of the monozygotic twins diagnosed to
have IHPS.
Front Med Case Rep, ISSN: 2582-8142 https://www.jmedicalcasereports.org/ 3Case Report Ayasa LA et al., 2022; 3(2): 1-05
DOI: http://dx.doi.org/10.47746/FMCR.2022.3206
Discussion
IHPS is one of the most common gastrointestinal disease among infants (Galea and Said 2018).
The cause of IHPS is still to be identified but it is believed to be multifactorial involving environmental
factors, genetic factors, and certain antibiotics. In a study that included a cohort of all children born in
Denmark between 1977-2008, the authors report a significant relationship between IHPS and maternal
smoking, male sex, premature birth, small for gestational age (SGA) newborns, cesarean delivery, and
first-born children (Krogh et al., 2012). The same study supported the presence of a strong genetic
component in the pathophysiology of IHPS, given the high incidence rate in monozygotic (200-fold higher
rate) and dizygotic twins (20-fold) (Krogh et al., 2010). A family history of IHPS is regarded as one of the
main risk factors for developing the disease, signifying the relevance of genetics role (Chung, 2008;
Rasmussen et al., 1989). The Danish children study estimated the heritability to be 87% (Krogh et al.,
2010); it also states that a newborn with an affected monozygotic twin was 6 times more likely to develop
the disease than a newborn with an affected dizygotic twin (Krogh et al., 2010), albeit the presence of
very few studies that documented few cases where there was no difference in the incidence between
monozygotic and dizygotic twins (MacMahon, 2006). Using Oral Erythromycin is considered one of the
risk factors as well, especially if it is administered during the first two weeks of life (Eberly et al., 2015).
IHPS patients typically present at the age of 3-6 weeks complaining of postprandial, projectile
vomiting of non-bilious gastric content (Shaoul et al., 2004). It is usually followed by the urge to be refed
(good appetite). Laboratory tests tend to show hyperchloremic, hypokalemic metabolic alkalosis. It is,
however, reported in various papers that significant electrolyte derangements is not a consistent finding
anymore since infants are better nourished nowadays (Taylor et al., 2013). The “olive” sign,
pathognomonic, on palpation in abdominal examination is also a highly relevant finding with a decreasing
incidence due to the recent dependency on imaging modalities, ultrasound in particular, to diagnose IHPS
(Vinycomb et al., 2019; Bakal et al., 2016).
Regardless of the abundance of the factors that argue for a genetic contribution, the diversity of
the risk factors, discordance in the development of IHPS in twins, and the absence of a clear inheritance
pattern have led researchers to propose other modes of inheritance, one of which was proposed in 1961
by Carter and Evan: the multifactorial threshold (MFT) model of inheritance (Carter and Evans, 1969). It
suggests that IHPS has a polygenic inheritance involving multiple genes and argues that the risk of having
IHPS is due to the synergistic effects of genetic and environmental factors, meaning that genes only
increase the risk, but environmental factors are required for the disease to manifest its clinical symptoms,
surpass a critical threshold, and refutes the hypothesis of the disease’s inheritance following the
Mendelian model.
Front Med Case Rep, ISSN: 2582-8142 https://www.jmedicalcasereports.org/ 4Case Report Ayasa LA et al., 2022; 3(2): 1-05
DOI: http://dx.doi.org/10.47746/FMCR.2022.3206
The explanation behind the family aggregation remains to be explained, and it is uncertain
whether it is mostly due to genes, maternal factors affecting in utero development, or environmental
factors.
Competing Interests: None.
Patient Consent: Obtained.
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