Very rare defects: what can we learn?

Symmetrical parapagus diprosopus: A comparative, computed tomographic, and pathoanatomical study of a new case in domestic pig

BACKGROUND

Parapagus diprosopus are conjoined twins characterized by craniofacial duplication and only one body, representing one of the rarest types of these twins. Their occurrence has been recorded in different species of vertebrates, including humans, but few cases have been studied in domestic pigs.

CASE

A pair of conjoined twin pigs was studied using x-rays, computed tomography, and necropsy. The abnormalities found were compared with those of the rare swine cases presented in the literature as well as with other species, and the different etiopathogenetic possibilities were addressed. The degree of duplication of the head bones decreased caudally, as did that of the structures of the central nervous system. In the two oral cavities, there was a complete cleft palate. All the cervical vertebrae and thoracic vertebrae up to T3 were partially duplicated. The heart and great vessels were normal, as were the other thoracic and abdominal organs.

CONCLUSIONS

The conjoined twin pigs of this study are a case of parapagus diprosopus tetraophthalmus triotus, presenting the same pattern of abnormalities of human diprosopus and that of other species. The scarcity of detailed studies on craniofacial duplication in pigs and the lack of a definitive explanation on the etiology and pathogenesis of conjoined twins shows the need for further research and the publication of more cases.

Amelia and phocomelia in Finland: Characteristics and prevalences in a nationwide population‐based study

BACKGROUND

Amelia and phocomelia represent severe limb reduction defects. Specific epidemiologic data on these defects are scarce. We conducted a descriptive analysis of prevalence data in Finland during 1993-2008 to clarify the epidemiology nationwide in a population-based register study. We hypothesized that increasing maternal age would affect the total prevalence of each disorder.

MATERIALS AND METHODS

We collected information on all fetuses and infants affected by amelia and phocomelia during 1993-2008 from the National Register of Congenital Malformations in Finland. The clinical, laboratory, autopsy, and imaging data were re-evaluated where available for all cases found.

RESULTS

A total of 23 amelia and 7 phocomelia patients were identified. Thalidomide was not an etiological factor in any of the cases. The total prevalence of amelia was 2.43 per 100,000 births. The live birth prevalence was 0.63 per 100,000 live births. The total prevalence of phocomelia was 0.74 per 100,000 births, and the live birth prevalence was 0.53 per 100,000 live births. Infant mortality in amelia and phocomelia was 67% and 60%, respectively.

CONCLUSIONS

Infant mortality is high among amelia and phocomelia. Most cases had other major associated anomalies, but syndromic amelia cases were rare. Total prevalences were higher than previously reported and showed an increase in prevalence toward the end of the study period. The percentage of elective terminations of pregnancy for these disorders is high. While isolated cases are rare, they most likely present a better prognosis. Thus, correct diagnosis is essential in counseling for possible elective termination.

Survival of children with rare structural congenital anomalies: a multi-registry cohort study

BACKGROUND

Congenital anomalies are the leading cause of perinatal, neonatal and infant mortality in developed countries. Large long-term follow-up studies investigating survival beyond the first year of life in children with rare congenital anomalies are costly and sufficiently large standardized cohorts are difficult to obtain due to the rarity of some anomalies. This study aimed to investigate the survival up to 10 years of age of children born with a rare structural congenital anomaly in the period 1995-2014 in Western Europe.

METHODS

Live births from thirteen EUROCAT (European network for the epidemiological surveillance of congenital anomalies) population-based registries were linked to mortality records. Survival for 12,685 live births with one of the 31 investigated rare structural congenital anomalies (CAs) was estimated at 1 week, 4 weeks and 1, 5 and 10 years of age within each registry and combined across Europe using random effects meta-analyses. Differences between registries were evaluated for the eight rare CAs with at least 500 live births.

RESULTS

Amongst the investigated CAs, arhinencephaly/holoprosencephaly had the lowest survival at all ages (58.1%, 95% Confidence Interval (CI): 44.3-76.2% at 1 week; 47.4%, CI: 36.4-61.6% at 1 year; 35.6%, CI: 22.2-56.9% at 10 years). Overall, children with rare CAs of the digestive system had the highest survival (> 95% at 1 week, > 84% at 10 years). Most deaths occurred within the first four weeks of life, resulting in a 10-year survival conditional on surviving 4 weeks of over 95% for 17 out of 31 rare CAs. A moderate variability in survival between participating registries was observed for the eight selected rare CAs.

CONCLUSIONS

Pooling standardised data across 13 European CA registries and the linkage to mortality data enabled reliable survival estimates to be obtained at five ages up to ten years. Such estimates are useful for clinical practice and parental counselling.

Prune belly syndrome in Finland - A population-based study on current epidemiology and hospital admissions

BACKGROUND

Prune belly syndrome (PBS) is a multisystem disease characterized by absent or deficient abdominal musculature with accompanying lax skin, urinary tract abnormalities, and cryptorchidism. Previous studies have estimated a birth prevalence of 1 in 35,000-50,000 live births.

OBJECTIVE

We set out to clarify the epidemiology and early hospital admissions of PBS in Finland through a population-based register study. Further, possible maternal risk factors for PBS were analyzed in a case-control setting.

STUDY DESIGN

The Finnish Register of Congenital Malformations was linked to the Care Register for Health Care, a population-based hospital admission data for PBS patients. Additionally, five matched controls were identified in the Birth Register and maternal risk factors of PBS were studied utilizing data from the Drugs and Pregnancy database.

RESULTS

We identified 31 cases of PBS during 1993-2015, 15 of which were live born and 16 elective terminations. The total prevalence was 1 in 44,000 births. Three patients (20%) died during infancy. On average, PBS-patients had 3.2 admissions and 10.6 hospital days per year in Finland during the study period years 1998-2015, 35- and 27-fold compared to children in Finland in general. Multiple miscarriages were significantly associated to PBS in maternal risk factor analyses.

DISCUSSION

The burden of disease is significant in PBS, demonstrated as a high infant mortality rate (20%), multiple hospital admissions, and inpatient care in days. The available variables are limited as a register-based study.

CONCLUSION

We present data on contemporary epidemiology in a population-based study and show that the total prevalence of PBS is 1 in 44,000 in Finland. PBS entails a significant disease burden with admissions and hospital days over 35- and 27-fold compared to the general pediatric population, further aggravated by an infant mortality rate of 20%.

Isolated postaxial polydactyly: Epidemiologic characteristics from a multicenter birth defects study

Isolated postaxial polydactyly (I-PAP), as a single defect, is a frequent malformation, characterized by an extra digit placed on the ulnar or fibular side of the limbs. Worldwide prevalence varies from as high as 225/10,000 in Nigerians to so low as 6.08/10,000 in Argentinians. Genetic-ethnic background significantly affects worldwide prevalence and type of I-PAP. Herein we describe the epidemiological characteristics of I-PAP in 697 newborns, 383 males and 314 females identified in 1,178,993 examined live births from a multicenter case-control hospital-based population study, the Mexican program of Registry and Epidemiological Surveillance of Congenital Malformations (RYVEMCE). The main characteristics analyzed included total I-PAP, stratified in Types A and B, defined as complete or incomplete extra-digit formation, respectively, sex prevalence, affected limb, laterality, parity, prematurity, delivery-type, twinning, consanguinity, and parental age. Males (6.35/10,000) are significantly more frequently affected than females (5.45/10,000), hands more than feet, left more than right limbs, and Type B (74.50%) more than A (25.50%). Prematurity and forceps use were significantly more frequent in cases than controls. An evident decreasing time-trend prevalence was present. Similar findings with other studies were males, upper and left limbs more frequently affected. Findings that were not previously reported include prematurity, forceps use, a significant decreasing time trend and an inverse ethnic prevalence for Types A (75%) and B (25%) in the Mayan population in contrast to other worldwide ethnic groups.

Diprosopus: Systematic review and report of two cases

BACKGROUND

Diprosopus is a subtype of symmetric conjoined twins with one head, facial duplication and a single trunk. Diprosopus is a very rare congenital anomaly.

METHODS

This is a systematic review of published cases and the presentation of two new cases born in Argentina. We estimated the prevalence of conjoined twins and diprosopus using data from the National Network of Congenital Anomalies of Argentina (RENAC).

RESULTS

The prevalence of conjoined twins in RENAC was 19 per 1,000,000 births (95% confidence interval, 12-29). Diprosopus prevalence was 2 per 1,000,000 births (95% confidence interval, 0.2-6.8). In the systematic review, we identified 31 diprosopus cases. The facial structures more frequently duplicated were nose and eyes. Most frequent associated anomalies were: anencephaly, duplication of cerebral hemispheres, craniorachischisis, oral clefts, spinal abnormalities, congenital heart defects, diaphragmatic hernia, thoracic and/or abdominal visceral laterality anomalies. One of the RENAC cases and three cases from the literature had another discordant nonmalformed twin.

CONCLUSION

The conjoined twins prevalence was similar to other studies. The prevalence of diprosopus was higher. The etiology is still unknown. The presence of visceral laterality anomalies may indicate the link between diprosopus and the alteration or duplication of the primitive node in the perigastrulation period (12-15 days postfertilization). Pregnancies of more than two embryos may be a risk factor for diprosopus. Given the low prevalence of this defect, it would be useful to perform studies involving several surveillance systems and international consortiums. Birth Defects Research (Part A), 2016. © 2016 Wiley Periodicals, Inc. Birth Defects Research (Part A) 106:993-1007, 2016. © 2016 Wiley Periodicals, Inc.

Sirenomelia in Argentina: Prevalence, geographic clusters and temporal trends analysis

BACKGROUND

Sirenomelia is a severe malformation of the lower body characterized by a single medial lower limb and a variable combination of visceral abnormalities. Given that Sirenomelia is a very rare birth defect, epidemiological studies are scarce. The aim of this study is to evaluate prevalence, geographic clusters and time trends of sirenomelia in Argentina, using data from the National Network of Congenital Anomalies of Argentina (RENAC) from November 2009 until December 2014.

METHODS

This is a descriptive study using data from the RENAC, a hospital-based surveillance system for newborns affected with major morphological congenital anomalies. We calculated sirenomelia prevalence throughout the period, searched for geographical clusters, and evaluated time trends.

RESULTS

The prevalence of confirmed cases of sirenomelia throughout the period was 2.35 per 100,000 births. Cluster analysis showed no statistically significant geographical aggregates. Time-trends analysis showed that the prevalence was higher in years 2009 to 2010.

CONCLUSION

The observed prevalence was higher than the observed in previous epidemiological studies in other geographic regions. We observed a likely real increase in the initial period of our study. We used strict diagnostic criteria, excluding cases that only had clinical diagnosis of sirenomelia. Therefore, real prevalence could be even higher. This study did not show any geographic clusters. Because etiology of sirenomelia has not yet been established, studies of epidemiological features of this defect may contribute to define its causes. Birth Defects Research (Part A) 106:604-611, 2016. © 2016 Wiley Periodicals, Inc.

Sirenomelia: two cases in Cali, Colombia

We report two cases of sirenomelia, a rare congenital defect with a prevalence rate of 1:100 000 births; both cases were observed in Cali, Colombia. Both pregnant women were referred from Buenaventura, Colombia. The expecting mothers shared multiple adverse sociodemographic factors. Their homes were located in a city where the entire population is of low socioeconomic status living under conditions of extreme poverty. They were uneducated, with nutritional deficiencies and no access to drinking water most of the time. Both were exposed to water and fish from a nearby river contaminated with leachate from a poorly managed landfill. A similar relation was previously reported in Cali in 2005 between environmental factors and sirenomelia. We suggest that there is a common aetiological factor of environmental origin between these two sirenomelia cases and propose that exposure to derivatives from landfills should be included among the factors for this rare defect of multifactorial aetiological origin.

Two iniencephaly cases born the same day in the same hospital of Cali, Colombia. Iniencephaly cluster?

Two patients with short and hyperextended neck, cervical meningocele and other birth defects, were born the same day at the same hospital, both died. The autopsy report and X-rays show iniencephaly's classic findings. Revision of clinical histories did not show consanguinity between the parents, or exposure to environmental factors.

Phocomelia: a worldwide descriptive epidemiologic study in a large series of cases from the International Clearinghouse for Birth Defects Surveillance and Research, and overview of the literature

Epidemiologic data on phocomelia are scarce. This study presents an epidemiologic analysis of the largest series of phocomelia cases known to date. Data were provided by 19 birth defect surveillance programs, all members of the International Clearinghouse for Birth Defects Surveillance and Research. Depending on the program, data corresponded to a period from 1968 through 2006. A total of 22,740,933 live births, stillbirths and, for some programs, elective terminations of pregnancy for fetal anomaly (ETOPFA) were monitored. After a detailed review of clinical data, only true phocomelia cases were included. Descriptive data are presented and additional analyses compared isolated cases with those with multiple congenital anomalies (MCA), excluding syndromes. We also briefly compared congenital anomalies associated with nonsyndromic phocomelia with those presented with amelia, another rare severe congenital limb defect. A total of 141 phocomelia cases registered gave an overall total prevalence of 0.62 per 100,000 births (95% confidence interval: 0.52-0.73). Three programs (Australia Victoria, South America ECLAMC, Italy North East) had significantly different prevalence estimates. Most cases (53.2%) had isolated phocomelia, while 9.9% had syndromes. Most nonsyndromic cases were monomelic (55.9%), with an excess of left (64.9%) and upper limb (64.9%) involvement. Most nonsyndromic cases (66.9%) were live births; most isolated cases (57.9%) weighed more than 2,499 g; most MCA (60.7%) weighed less than 2,500 g, and were more likely stillbirths (30.8%) or ETOPFA (15.4%) than isolated cases. The most common associated defects were musculoskeletal, cardiac, and intestinal. Epidemiological differences between phocomelia and amelia highlighted possible differences in their causes.

Sirenomelia: an epidemiologic study in a large dataset from the International Clearinghouse of Birth Defects Surveillance and Research, and literature review

Sirenomelia is a very rare limb anomaly in which the normally paired lower limbs are replaced by a single midline limb. This study describes the prevalence, associated malformations, and maternal characteristics among cases with sirenomelia. Data originated from 19 birth defect surveillance system members of the International Clearinghouse for Birth Defects Surveillance and Research, and were reported according to a single pre-established protocol. Cases were clinically evaluated locally and reviewed centrally. A total of 249 cases with sirenomelia were identified among 25,290,172 births, for a prevalence of 0.98 per 100,000, with higher prevalence in the Mexican registry. An increase of sirenomelia prevalence with maternal age less than 20 years was statistically significant. The proportion of twinning was 9%, higher than the 1% expected. Sex was ambiguous in 47% of cases, and no different from expectation in the rest. The proportion of cases born alive, premature, and weighting less than 2,500 g were 47%, 71.2%, and 88.2%, respectively. Half of the cases with sirenomelia also presented with genital, large bowel, and urinary defects. About 10-15% of the cases had lower spinal column defects, single or anomalous umbilical artery, upper limb, cardiac, and central nervous system defects. There was a greater than expected association of sirenomelia with other very rare defects such as bladder exstrophy, cyclopia/holoprosencephaly, and acardia-acephalus. The application of the new biological network analysis approach, including molecular results, to these associated very rare diseases is suggested for future studies.

Conjoined twins: a worldwide collaborative epidemiological study of the International Clearinghouse for Birth Defects Surveillance and Research

Conjoined twins (CT) are a very rare developmental accident of uncertain etiology. Prevalence has been previously estimated to be 1 in 50,000 to 1 in 100,000 births. The process by which monozygotic twins do not fully separate but form CT is not well understood. The purpose of the present study was to analyze diverse epidemiological aspects of CT, including the different variables listed in the Introduction Section of this issue of the Journal. The study was made possible using the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR) structure. This multicenter worldwide research includes the largest sample of CT ever studied. A total of 383 carefully reviewed sets of CT obtained from 26,138,837 births reported by 21 Clearinghouse Surveillance Programs (SP) were included in the analysis. Total prevalence was 1.47 per 100,000 births (95% CI: 1.32-1.62). Salient findings including an evident variation in prevalence among SPs: a marked variation in the type of pregnancy outcome, a similarity in the proportion of CT types among programs: a significant female predominance in CT: particularly of the thoracopagus type and a significant male predominance in parapagus and parasitic types: significant differences in prevalence by ethnicity and an apparent increasing prevalence trend in South American countries. No genetic, environmental or demographic significant associated factors were identified. Further work in epidemiology and molecular research is necessary to understand the etiology and pathogenesis involved in the development of this fascinating phenomenon of nature.

Amelia: a multi-center descriptive epidemiologic study in a large dataset from the International Clearinghouse for Birth Defects Surveillance and Research, and overview of the literature

This study describes the epidemiology of congenital amelia (absence of limb/s), using the largest series of cases known to date. Data were gathered by 20 surveillance programs on congenital anomalies, all International Clearinghouse for Birth Defects Surveillance and Research members, from all continents but Africa, from 1968 to 2006, depending on the program. Reported clinical information on cases was thoroughly reviewed to identify those strictly meeting the definition of amelia. Those with amniotic bands or limb-body wall complex were excluded. The primary epidemiological analyses focused on isolated cases and those with multiple congenital anomalies (MCA). A total of 326 amelia cases were ascertained among 23,110,591 live births, stillbirths and (for some programs) elective terminations of pregnancy for fetal anomalies. The overall total prevalence was 1.41 per 100,000 (95% confidence interval: 1.26-1.57). Only China Beijing and Mexico RYVEMCE had total prevalences, which were significantly higher than this overall total prevalence. Some under-registration could influence the total prevalence in some programs. Liveborn cases represented 54.6% of total. Among monomelic cases (representing 65.2% of nonsyndromic amelia cases), both sides were equally involved, and the upper limbs (53.9%) were slightly more frequently affected. One of the most interesting findings was a higher prevalence of amelia among offspring of mothers younger than 20 years. Sixty-nine percent of the cases had MCA or syndromes. The most frequent defects associated with amelia were other types of musculoskeletal defects, intestinal, some renal and genital defects, oral clefts, defects of cardiac septa, and anencephaly.

Bladder exstrophy: an epidemiologic study from the International Clearinghouse for Birth Defects Surveillance and Research, and an overview of the literature

Bladder exstrophy (BE) is a complex congenital anomaly characterized by a defect in the closure of the lower abdominal wall and bladder. We aimed to provide an overview of the literature and conduct an epidemiologic study to describe the prevalence, and maternal and case characteristics of BE. We used data from 22 participating member programs of the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR). All cases were reviewed and classified as isolated, syndrome, and multiple congenital anomalies. We estimated the total prevalence of BE and calculated the frequency and odds ratios for various maternal and case characteristics. A total of 546 cases with BE were identified among 26,355,094 births. The total prevalence of BE was 2.07 per 100,000 births (95% CI: 1.90-2.25) and varied between 0.52 and 4.63 among surveillance programs participating in the study. BE was nearly twice as common among male as among female cases. The proportion of isolated cases was 71%. Prevalence appeared to increase with increasing categories of maternal age, particularly among isolated cases. The total prevalence of BE showed some variations by geographical region, which is most likely attributable to differences in registration of cases. The higher total prevalence among male cases and older mothers, especially among isolated cases, warrants further attention.