Anorectal Malformations in Male Monozygotic Twins and Review of Literature.

Anorectal malformations (ARMs) are one of the common congenital gastrointestinal malformations with a prevalence of 0.2-0.6/1000 live births. There are only a few reported cases of familial ARMs in literature suggesting different patterns of inheritance. Among them, isolated ARMs in monozygotic twins are quite rare with significant male preponderance. Most of these ARMs are either of intermediate or low anomaly type. We reported two pairs of male monozygotic isolated ARMs from a tertiary care hospital in India and reviewed the literature in details adding to the total of nine pairs of twins till date. Copyright:

INTRODUCTION

Among congenital anomalies of the gastrointestinal tract, anorectal malformations (ARMs) are the most common with a prevalence of 0.2–0.6/1000 live births.[1] ARM is a complex anomaly, in which there is absent anal opening with communication with urinary system. ARMs can be classified into high, intermediate, and low types depending on the level of termination of rectal pouch in relation with pubococcygeal line and ischial lines.[2] There are few cases reported in literature in relation to familial ARMs suggesting different patterns of inheritance.[34] Here, we studied two cases of isolated male ARMs in monozygotic twins and reviewed the literature in details.

CASE REPORTS

We studied these two male monozygotic twins with ARMs reported in the department of pediatric surgery in our hospital.

Pair 1

This is a brief case history of full-term, normal vaginally delivered male monozygotic twins. Birth weights of twins were 1.96 kg and 2.10 kg, respectively. Both twins presented in vertex presentation and had normal antenatal ultrasonography (USG) done in the third trimester. The pregnancy was uneventful with a family history of twining from maternal side. There was no family history of any congenital malformation from both paternal and maternal sides. On physical examination, both the twins presented at 8 h after birth with absent anal opening, and were active, good cry, pink in color, with no respiratory distress, and were admitted in surgical neonatal intensive care (NICU). On perineal examination, both had absent anal opening with small hyperpigmented area with anal dimple at proposed anal site with well-formed gluteal folds, normal testes and phallus [Figure 1]. There was no other congenital anomaly. Invertogram done 24 h after birth showed intermediate type of ARM. USG abdomen and pelvis was normal. Echocardiogram was also normal. There were no associated vertebral defects. Chest X-ray of both twins was within acceptable range. High divided sigmoid colostomy was planned in both cases. Postoperative period was uneventful and both of the twins were discharged on day 10 after good general condition, and subsequently, posterior sagittal anorectoplasty (PSARP) was done. Both of these twins had rectobulbar urethral fistula. Colostomy closure was done after 8 weeks of PSARP. Both the twins are presently on regular follow-up with good continence.

Figure 1

Perineum of pair 1 monozygotic twins

Pair 2

Newly reported male twins born at 36-week gestation by cesarean section presented in surgical NICU with absent anal opening. Antenatal USG scans confirmed the diagnosis of twins and breech position of both babies. There was no family history of twinning and any other congenital anomaly in a family. Birth weights of both twins were 1.76 kg and 1.86 kg, respectively. On initial physical examination, both were active, with mild respiratory distress. On local perineal examination, both had absent anal opening with well-formed gluteal folds and well-formed scrotum [Figure 2]. There was no history of meconuria in babies. USG abdomen and pelvis showed unilateral renal agenesis in one of the twins and the other twin had normal USG. Echocardiogram and USG spine was also normal. Prone cross-table X-ray done after 24 h showed intermediate ARM in one neonate and low ARM in the other neonate. High-pressure colostogram was done in the first neonate which showed fistula at the bulbar urethra region. PSARP was done in the first neonate. Stoma closure was done after 12 weeks. At present, both twins are on regular follow-up with occasional fecal soiling.

Figure 2

Perineum of pair 2 monozygotic twins

DISCUSSION

Among congenital birth defects of the digestive tract, ARMs are among common problems with a birth prevalence of 0.2–0.6/1000 live births.[1] The etiology of ARM is less known, most of the scientific research points toward genetic factors as an important cause.[5] Role of various genes and environmental factors has been established in details.[67] ARM can be divided into two main groups from genetic aspect: syndromic ARM and isolated ARM which includes one-third of all cases. Both are considered to have different etiologies.[8] The isolated ARMs are most commonly associated with an autosomal dominant inheritance and familial ones have dominant, recessive as well as sex-linked inheritances.[91011]

The frequency of congenital anomalies of the lower gastrointestinal tract including ARMs has been reported to be higher in twins.[12] Hadra first time in 1885 described ARM in siblings, and both of these had probably severe form of ARM and died shortly after birth.[13] Many research papers were published thereafter on ARM in siblings, in contrast to isolated ARM in twins. The first such reported case of ARM in twins dates back to 1939 by Feggetter, where both twins were males and had isolated low ARM and managed by anoplasty[14] [Table 1]. Another study by Cozzi and Wilkinson in 1968 reported two pairs of male twins with isolated low type of ARM, managed by anoplasty.[11] Christensen et al. in 1990 reported another pair of female ARMs, managed by colostomy and definitive surgery later.[15] Kubiak and Upadhyay in 2005 did a detailed review of literature to find the correlation between siblings/twins and ARM. They studied 19 cases with isolated ARM in siblings, out of which only 5 cases of monozygotic twins with low-type ARMs were identified.[16] de Buys Roessingh et al. in 2009 described intermediate type of ARM in male monozygotic twins with Down syndrome. Both these twins were initially managed by colostomies followed by laparoscopic abdominal pull through.[17] Another study by Tsoraides et al. in 2016 reported isolated type of ARM (intermediate) in male twins managed initially by transverse loop colostomy and planned anoplasty at later date.[18]

Table 1

Details of cases of anorectal malformations in monozygotic twins from literature

Author (year)	Sex of both twins	Type of ARM	Surgical procedure done	Associated anomaly
Feggetter S. (1939)	Both males	Low ARM	Anoplasty	Nil
Cozzi et al. (1968)	Case A, both males	Low ARM	Anoplasty	Nil
	Case B, both males	Low ARM	Anoplasty	Nil
Christensen K et al. (1990)	Both females	Low ARM	Colostomy and limited PSARP	Nil
Kubiak R et al. (2005)	Both males	Low ARM (anocutaneous fistula)	Y-V anoplasty	Nil
Anthony S. De Buys Roessingh et al. (2009)	Both males	Low/intermediate ARM	Initial colostomy followed by laparoscopic abdominal pull through	Down syndrome
Tsoraides SS et al. (2016)	Both males	Intermediate ARM	Transverse loop colostomy and planned anoplasty	Nil
Our study (2020)	Pair 1, both males	Both intermediate ARM	High divided sigmoid colostomy followed 1 year later by PSARP and stoma closure 8 weeks later	Nil
	Pair 2, both males	One intermediate ARM	In one initial colostomy followed by PSARP later and stoma closure 12 weeks later	Patent ductus arteriosus
		One low ARM	V-Y anoplasty	Nil

ARM: Anorectal malformation, PSARP: Posterior sagittal anorectoplasty

Similarly, we reported two pairs of monozygotic twins as Pair 1 and Pair 2. One of the twins in pair 1, both neonates were term male with intermediate ARM and colostomy followed by PSARP and stoma closure later, was done. There was no associated congenital anomaly in pair A. In pair 2, one male twin was intermediate type of ARM with small patent ductus arteriosus, which was managed by initial colostomy followed by PSARP and stoma closure later, and the other was low ARM, managed by anoplasty. One neonate was initially followed up with regular anal dilatation and now has acceptable level of continence.

In total, 9 cases of monozygotic twins with isolated ARM have been identified with clinical details to the best of our knowledge. There were seven male twins and two female twins, mostly with low/intermediate ARM. Detailed review of literature confirms that isolated ARM occurs more commonly with low/intermediate type of anomalies, where associated congenital anomalies are less common. There are several genetic factors that explain this association. In isolated ARM, explanations are based on developmental field theory, which describes that entire embryo during blastogenesis is the progenitor field that behaves in an organized fashion.[19] The disturbance in this phase of blastogenesis results in cases of isolated ARM, resulting in a single anomaly.[20] The role of environmental factors related to causation of isolated ARM is also not clear in most of the patients. Management of these cases of isolated ARM in twins needs careful clinical examination of the perineum to look for the presence of fistula and detailed radiographic examination of all visible orifices. Protective colostomy should always be favored initially if there is doubt about the type of anomaly, followed by anorectoplasty either by posterior sagittal approach or perineal approach.

In conclusion, cases of isolated ARM in monozygotic twins are rare. Detailed review has shown that cases of isolated ARM have male preponderance, with higher rate of twinning. Our findings also conclude that most of these cases of isolated ARM have either low or intermediate anomaly. Further research on familial cases of isolated ARM can help to explain the pathogenesis and exact pattern of inheritance in these types of anomalies. We hope our two pairs of twins with isolated ARM contribute positively to the literature.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.