Clustering of malformations in the families of South American oral cleft neonates

Genetics and management of the patient with orofacial cleft

Cleft lip or palate (CL/P) is a common facial defect present in 1 : 700 live births and results in substantial burden to patients. There are more than 500 CL/P syndromes described, the causes of which may be single-gene mutations, chromosomopathies, and exposure to teratogens. Part of the most prevalent syndromic CL/P has known etiology. Nonsyndromic CL/P, on the other hand, is a complex disorder, whose etiology is still poorly understood. Recent genome-wide association studies have contributed to the elucidation of the genetic causes, by raising reproducible susceptibility genetic variants; their etiopathogenic roles, however, are difficult to predict, as in the case of the chromosomal region 8q24, the most corroborated locus predisposing to nonsyndromic CL/P. Knowing the genetic causes of CL/P will directly impact the genetic counseling, by estimating precise recurrence risks, and the patient management, since the patient, followup may be partially influenced by their genetic background. This paper focuses on the genetic causes of important syndromic CL/P forms (van der Woude syndrome, 22q11 deletion syndrome, and Robin sequence-associated syndromes) and depicts the recent findings in nonsyndromic CL/P research, addressing issues in the conduct of the geneticist.

Parental consanguinity in specific types of congenital anomalies

Parental consanguinity, as a recognized risk factor for congenital anomalies, has mainly been studied with a focus on the types of parental relationships and their effects on genetic syndromes or birth defects in general. The present work analyzed the association between parental consanguinity and congenital anomalies, split, when possible, into clinical subtypes, in an attempt to obtain some insight into their recognized etiological heterogeneity. The material consisted of 34,102 newborn infants, affected by one of 47 selected congenital anomaly types, ascertained by the Latin-American Collaborative Study of Congenital Malformations (ECLAMC) during the period from 1967 to 1997. The consanguinity rate for each congenital anomaly type was compared with that of the population under study (0.96%), and the potentially confounding effect of six selected variables was controlled through a conditional logistic regression analysis for those congenital anomalies significantly associated with consanguinity. Pre-occurrence rates for the same congenital anomaly in sibships of consanguineous and non-consanguineous cases were compared. A significant association with parental consanguinity was observed for three congenital anomaly types: hydrocephalus, postaxial hand polydactyly, and bilateral cleft lip +/- cleft palate, while three additional anomalies, namely, cephalocele, microcephaly, and hand + foot postaxial polydactyly, showed a positive association, but statistical significance disappeared after adjustment for confounders, probably owing to sample size reduction. The association between consanguinity and Down syndrome was mainly due to the confounding effect of maternal age, while for hydrops fetalis and 2-3 toe syndactyly, the observed positive association could not be tested for confounders due to sample size reduction.

An epidemiologic study of oral clefts in Iran: analysis of 1,669 cases

OBJECTIVE

The objective of this study was to assess the epidemiology and some genetic aspects of oral clefting in Iran.

DESIGN

The study was a 15-year cross-sectional (prevalence) study from August 1976 to September 1991.

SETTING

The setting for the study was two plastic surgery departments, both mostly referral centers, and a maternity hospital in Iran.

PARTICIPANTS

The participants were 1,669 consecutive surgical cases with oral clefts (79% between 1 day and 18 months of age), registered in two centers. In a parallel study, 19,369 livebirths born in a maternity hospital within the same period were surveyed to ascertain prevalence of clefting at birth. Normal children of this population were used as the control group. Samples were analyzed by prevalence of clefting at birth, type of oral cleft, side of clefting, sex ratio, associated malformations, clefts in relatives, and parental consanguinity.

RESULTS

The prevalence of clefts was 1.03 per 1,000 births. Cleft lip (without cleft palate) had a higher (34.9%) and cleft palate alone had a significantly lower prevalence (17.4%) than expected. Cleft lip (without cleft palate) was more common in females (53.6%) than in males (46.4%). The rate of associated malformations in cleft patients (7.73%) was higher than in controls (0.093%). Association between clefting and consanguinity was significant (45.8% in cases versus 43.1% in controls). Occurrence of noncleft congenital malformations among first-degree relatives of our cases (2.77%) was nearly two times that of controls (1.55%).

CONCLUSION

Our study reveals that the population incidence of oral clefts in Iran is much closer to European than Arab-African or South East Asian countries. However, significant variations in other epidemiologic and some genetic features were observed.

Nonsyndromic cleft lip and palate is not associated with cancer or other birth defects

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is one of the most common human malformations with an average prevalence of 1 in 1,000 live births. The cause(s) of NSCLP remain unclear as the relative roles of genes, of the environment, and/or of chance alone are unknown. The purpose of this study was to evaluate the potential role of environmental factors in the cause of NSCLP, to determine if other birth defects aggregate in families with at least one individual affected with NSCLP, and to investigate the frequency of cancer in the first- and second-degree relatives of NSCLP index-cases. Included in this study were 196 index-cases and their families. Information pertaining to environmental factors and pedigree information was obtained on each family. Analysis showed that no single environmental factor could explain the occurrence of NSCLP in this population. The frequency of other birth defects in these families was 1.2%, which is not increased over that in the general population. One hundred seven cancers were reported in 72 of the 196 families included in the study. The frequency of cancer was not significantly increased in the first- or second-degree relatives of the NSCLP index cases or in those families with a positive family history of NSCLP. No childhood or adult cancers were reported in any of the 196 NSCLP index cases.

766 cases of oral cleft in Italy. Data from Emilia Romagna (IMER) and northeast Italy (NEI) registers

Epidemiological and genetic variables for oral clefts were analysed for the years 1981-1989 in a case-control study of congenital malformations in the Emilia Romagna, Veneto, and Friuli regions, and in the Trento and Bolzano hospitals. Birth prevalence for all cases of cleft lip with or without cleft palate (CL(P)) was 8.2 per 10,000 births, and that for cleft palate only (CP) was 6.1 per 10,000. Coexisting abnormalities were found in 23% of CL(P) cases and in 43% of CP. No clusters in time or space were detected. For isolated clefts, a predominance of males among CL(P) and of females among CP was found; epilepsy was the only maternal risk factor correlated with clefts, and an association between clefting and consanguinity was found. Empirical recurrence risks were calculated in both isolated CL(P) and CP.