Choanal atresia and hypothelia following methimazole exposure in utero: a second report

Phenotypic expansion of KMT2D-related disorder: Beyond Kabuki syndrome

Pathogenic variants in KMT2D, which encodes lysine specific methyltransferase 2D, cause autosomal dominant Kabuki syndrome, associated with distinctive dysmorphic features including arched eyebrows, long palpebral fissures with eversion of the lower lid, large protuberant ears, and fetal finger pads. Most disease-causing variants identified to date are putative loss-of-function alleles, although 15-20% of cases are attributed to missense variants. We describe here four patients (including one previously published patient) with de novo KMT2D missense variants and with shared but unusual clinical findings not typically seen in Kabuki syndrome, including athelia (absent nipples), choanal atresia, hypoparathyroidism, delayed or absent pubertal development, and extreme short stature. These individuals also lack the typical dysmorphic facial features found in Kabuki syndrome. Two of the four patients had severe interstitial lung disease. All of these variants cluster within a 40-amino-acid region of the protein that is located just N-terminal of an annotated coiled coil domain. These findings significantly expand the phenotypic spectrum of features associated with variants in KMT2D beyond those seen in Kabuki syndrome and suggest a possible new underlying disease mechanism for these patients.

Maternal factors in the origin of infantile hypertrophic pyloric stenosis: A population-based case-control study

In most patients affected by isolated infantile hypertrophic pyloric stenosis (IHPS) the etiology is largely unknown. Thus, the aim of this study was to estimate possible maternal risk factors in the origin of IHPS. The study samples included 241 cases with IHPS, 357 matched controls and 38,151 population controls without any defect in the population-based large dataset of the Hungarian Case-Control Surveillance of Congenital Abnormalities, 1980-1996. Exposures that had been medically recorded in prenatal maternity logbooks during the critical period of IHPS were evaluated separately. The findings of this case-control study suggested that--beyond the well-known robust male excess (85.5%)--maternal hyperthyroidism (OR with 95% CI: 4.17, 1.53-11.38) and oral nalidixic acid treatment (OR with 95% CI: 6.53, 3.03-14.06) associated with a higher risk for IHPS in their children. In conclusion, our findings suggest that cases with IHPS had mothers with a higher proportion of hyperthyroidism and nalidixic acid treatment during pregnancy.

Current Updates on Choanal Atresia

Choanal atresia (CA) is a relatively uncommon but well-recognized condition characterized by the anatomical closure of the posterior choanae in the nasal cavity. Since the original description back in the early eighteenth century, there have been controversies regarding its exact pathogenesis, the optimal surgical approach, and the use of adjunct treatments such as post-surgical stenting and anti-neoplastic agents, despite of abundant literature available. The emergence and development of new technologies play a significant role in the management of this condition. This review provides a comprehensive clinical update on CA and identifies areas for future study based on the existing available literature.

Evaluation of developmental toxicity of propylthiouracil and methimazole

BACKGROUND

Propylthiouracil (PTU) and methimazole (MMI) are antithyroid drugs used to treat hyperthyroidism. Despite the widespread use of PTU and MMI during pregnancy, modest clinical data and less animal data are available on the teratogenic potential of these drugs.

METHODS

We evaluated the teratogenicity of in utero exposure to PTU or MMI in mice and rats. First, pregnant C57Bl/6 mice were treated daily with PTU (10 or 100 mg/kg), MMI (2 or 20 mg/kg), or vehicle from gestation day (GD) 6 to 16. GD 18 fetuses were evaluated for gross and histopathological abnormalities. Next, pregnant Sprague-Dawley rats were treated daily with PTU (50 or 100 mg/kg), MMI (10 or 20 mg/kg), or vehicle from GD 6 to 19, followed by evaluation for gross and histopathological abnormalities at GD 20.

RESULTS

In mice treated with PTU or MMI, no significant histopathological abnormalities or external gross malformations, and no adverse effects on placental weight, litter size, resorption rates, or fetal weight were observed at GD 18. In rats, no adverse effects on litter size, placental weights, or maternal body weights were observed with either PTU or MMI treatment. PTU treatment (50 and 100 mg/kg) and MMI (10 mg/kg) treatment resulted in a decrease in crown-rump length in rat fetuses but no external gross malformations or histopathological abnormalities were observed.

CONCLUSION

We did not observe either gross external malformations or histopathological malformations in mice or rats treated long-term with high doses of PTU or MMI during pregnancy.

Perinatal complications and higher risks of offspring thyroid dysfunction in early childhood of Graves' disease mothers with euthyroidism

AIM

To investigate the perinatal complications and risk of thyroid dysfunction at early childhood of Graves' disease (GD) mothers with euthyroidism (EU) or subclinical hyperthyroidism (sHT) during pregnancy.

METHOD

One hundred and twenty-three pregnant women with GD were recruited. They were all in euthyroidism with treatment of anti-thyroid drugs (ATDs) before pregnancy. All the pregnant GD women maintained EU (n=55) or sHT (n=68) by using ATDs. Sixty randomly selected, age-matched healthy pregnant women (non-GD control) were included. The prenatal and newborn data were collected and analyzed. Toddlers of GD mothers (n=45) and non-GD healthy mothers (n=36) were also recruited for thyroid function and growth assessments.

RESULTS

Newborns of mothers with GD had significantly higher complications than those of non-GD mothers. The percent of perinatal complications were 5.0%, 30.9% and 32.3% in the control, EU (vs. control, p<0.001), and sHT (vs. control, p<0.001) groups, respectively. There were no differences between the women continuing low doses of ATDs at the start of pregnancy and the women who stopped receiving ATDs at the start of pregnancy. Toddlers' serum levels of FT3, FT4, anti-thyroglobulin antibody, and anti-thyroid peroxidase antibody were significantly higher than those of non-GD mothers (all p<0.05).

CONCLUSION

Pregnancy with GD significantly increases the perinatal complications even with EU. The continued use of ATDs at the start of pregnancy does not give an increased risk of perinatal complications in GD mothers. Maternal GD may also induce a higher risk of autoimmue thyroid dysfunction among offspring at early childhood.

Carbimazole embryopathy: implications for the choice of antithyroid drugs in pregnancy

Maternal thyrotoxicosis, predominantly secondary to Graves' disease, affects 0.2% of all pregnancies. The Endocrine Society guidelines recommend the use of propylthiouracil as a first-line drug for thyrotoxicosis in pregnancy because of associations between carbimazole or methimazole and congenital anomalies. However, recent studies have highlighted the risk of severe liver injury with propylthiouracil. Here, we report another case with multiple congenital anomalies following in utero exposure to carbimazole and review the literature to consider the risks and benefits of available pharmacological treatments for thyrotoxicosis in pregnancy.

Choanal atresia associated with tracheoesophageal fistula: the spectrum of carbimazole embryopathy

This article focuses on the case of a newborn infant boy with bilateral choanal atresia, tracheoesophageal fistula, and bilateral fifth-finger clinodactyly. This infant had been exposed to carbimazole in utero during the treatment of maternal Graves disease. Teratogenic defects caused by carbimazole were recently recognized, and their phenotypes have been defined. Choanal atresia, esophageal atresia, athelia or hypothelia, developmental delay, hearing loss, and dysmorphic facial features have all been reported. To our knowledge, this is the first documented case of tracheoesophageal fistula without esophageal atresia (H type). Knowledge of the teratogenic potential of carbimazole is important when managing Graves disease in women of childbearing age.

Role of rare cases in deciphering the mechanisms of congenital anomalies: CHARGE syndrome research

In this review, our work on CHARGE syndrome will be used to exemplify the role of rare cases in birth defects research. The analysis of 29 cases with mutations of CHD7, the causative gene for CHARGE syndrome, clarified the relative importance of the cardinal features, including facial nerve palsy and facial asymmetry. Concurrently, in situ hybridization using chick embryos studies were performed to delineate the expression pattern of Chd7. The Chd7-positive regions in the chick embryos and the anatomical defects commonly seen in patients with CHARGE syndrome were well correlated: expression in the optic placode corresponded with defects such as coloboma, neural tube with mental retardation, and otic placode with ear abnormalities. The correlation between expression in the branchial arches and nasal placode with the clinical symptoms of CHARGE syndrome, however, became apparent when we encountered two unique CHARGE syndrome patients: one with a DiGeorge syndrome phenotype and the other with a Kallman syndrome phenotype. A unifying hypothesis that could explain both the DiGeorge syndrome phenotype and the Kallman syndrome phenotype in patients with CHARGE syndrome may be that the mutation in CHD7 is likely to exert its effect in the common branch of the two pathways of neural crest cells. As exemplified in CHARGE syndrome research, rare cases play a critical role in deciphering the mechanisms of human development. Close collaboration among animal researchers, epidemiologists and clinicians hopefully will enhance and maximize the scientific value of rare cases.

Grade 1 microtia, wide anterior fontanel and novel type tracheo-esophageal fistula in methimazole embryopathy

Carbimazole (CMZ) and its active metabolite methimazole (MMI) are antithyroid medications, which can result in MMI/CMZ embryopathy in susceptible individuals. The incidence of birth defects related to MMI/CMZ embryopathy remains unclear as several epidemiologic studies failed to prove a correlation, despite positive case-control studies and numerous case reports. Malformations reported in exposed individuals and commonly recognized as MMI/CMZ embryopathy include cutis aplasia of the scalp, choanal atresia, esophageal atresia (EA), tracheo-esophageal fistula (TEF), persistent vitelline duct, athelia/hypothelia, and subtle facial dysmorphisms including sparse or arched eyebrows. Here, we report on individuals with early pregnancy exposure to MMI, with microtia and various other anomalies associated with MMI embryopathy, suggesting that microtia is also seen with increased frequency after prenatal MMI exposure. Additional unusual malformations among our patients include a previously unreported type of TEF with three separate esophageal pouches and a fistula connecting the middle pouch to the trachea in one child, and absence of the gall bladder in another. An enlarged anterior fontanel was seen in three patients, and clinodactyly of the fifth finger was noted in three. The similarities between our three patients with microtia after MMI exposure and the two previously reported with microtia after CMZ exposure support the concept of microtia being related to the MMI/CMZ exposure. Recognition of microtia as a manifestation of MMI/CMZ embryopathy will likely increase the number of diagnosed cases and thus affect ascertainment. We propose diagnostic criteria for MMI/CMZ embryopathy, including the presence of at least one major characteristic finding.

Toxicological considerations for antithyroid drugs in children

INTRODUCTION

Propylthiouracil (PTU), methimazole (MMI) and carbimazole are indicated for the treatment of hyperthyroidism in adult and pediatric patients. The aim of this review is to present all the relevant information regarding the use of antithyroid drugs (ATD) in pediatric thyrotoxic cases, the pediatric toxicology of ATD and the warning which has recently been issued for PTU by the FDA.

AREAS COVERED

Epidemiology, diagnosis and treatment of pediatric thyrotoxicosis are all presented in this article. The authors also extensively discuss the details regarding the pharmacology, bioactivation, biodisposition, bioavailability and pharmacokinetic properties of the two main ATD (MMI and PTU).

EXPERT OPINION

The FDA recently reported that use of PTU is associated with a higher risk for clinically serious or fatal liver injury compared to MMI in both adult and pediatric patients. They also found that congenital malformations were reported approximately three times more often with prenatal exposure to MMI compared with PTU and especially with the use of MMI during the first trimester of pregnancy. The authors believe that PTU should not be used in pediatric patients unless the patient is allergic to or intolerant of MMI, and there are no other treatment options available. That being said, PTU may be the treatment of choice during, and just before, the first trimester of pregnancy.

Possible association between hyperthyroidism in pregnant women and obstructive congenital abnormalities of urinary tract in their offspring--a population-based case-control study

OBJECTIVE

The teratogenic potential of some antithyroid drugs is known, but the aim of the study was to estimate the risk of congenital abnormalities (CAs) in the offspring of pregnant women with hyperthyroidism with or without antithyroid drug treatment.

METHOD

Comparison of the occurrence of medically recorded hyperthyroidism who had malformed fetuses/newborns (cases) and who delivered healthy babies (controls) in the population-based Hungarian Case-Control Surveillance System of CAs, 1980-1996. Of 22,843 cases with congenital abnormalities, 71 (0.31%) while of 38,151 controls, 116 (0.30%) had mothers with hyperthyroidism. The rate of hyperthyroidism in the mothers of cases with different CAs and in the mothers of matched controls was compared.

RESULTS

Preeclampsia-eclampsia occurred more frequently in pregnant women with hyperthyroidism without antithyroid treatment. The analysis of specific groups of CAs showed an association between hyperthyroidism in pregnant women and obstructive defects of urinary tract in their children.

CONCLUSIONS

The lack of appropriate treatment of pregnant women affected with hyperthyroidism seems to be the major problem, because it would be necessary to prevent the hyperthyroidism related risks of pregnancy complications and CAs which exceed the risk of antithyroid medication in these pregnant women.

Choanal atresia associated with maternal hyperthyroidism treated with methimazole: a case-control study

Thyrotoxicosis affects 0.2% of pregnant women and antithyroid drugs are the treatment of choice during pregnancy. Several case reports have suggested a relationship between the prenatal use of methimazole (MMI) and choanal atresia in the offspring. However, two epidemiological studies did not find an increased teratogenic risk for MMI. This multicenter case-control study compared the frequency of maternal hyperthyroidism treated with MMI during pregnancy, in children with choanal atresia (cases) and a control group randomly selected (three matched controls according to maternal age for each case). Mothers of cases (N = 61) and controls (N = 183) were interviewed for socio-demographic questions, obstetrical and genetic history, and exposure during pregnancy to different agents; specifically detailed information regarding hyperthyroidism and MMI intake was obtained. Prenatal exposure to maternal hyperthyroidism treated with MMI was identified in 10/61 cases (16.4%) compared to 2/183 (1.1%) in the control group (OR = 17.75; CI95% = 3.49-121.40). Cases and controls did not differ in their parental degree of education, paternal occupation, twinning, maternal parity, and other exposures during pregnancy. Facial features in exposed cases showed some similarities. Our data suggest that prenatal exposure to maternal hyperthyroidism treated with MMI is associated with choanal atresia. In addition, based on our cases and a critical literature review, we propose that the mother's disease might be the causal factor and not the MMI treatment.

Report of a fourth individual with a lethal syndrome of choanal atresia, athelia, evidence of renal tubulopathy, and family history of neck cysts

In 1998, Hisama et al. described three brothers born following pregnancies complicated by oligohydramnios in the second or third trimester. Post-natal renal functions were compromised, and post-mortem studies showed kidney tissue abnormalities. Resuscitation and support were required, and they survived 25 hr to 12 days. All boys had a similar craniofacial appearance with infraorbital creases, low set dysplastic ears, as well as athelia, and broad digits with small nails. Variably present features were choanal atresia, preauricular tags and pits, branchial clefts, ventricular septal defect, type IIB interrupted aortic arch, pulmonary lobation anomaly, absent gallbladder, absent thymus, absent parathyroid gland, accessory spleen, and imperforate anus. Their mother, maternal grandmother, and maternal first cousin had neck cysts removed as children. We describe a female infant born following a pregnancy where oligohydramnios developed between 27 and 33 weeks gestation. Renal function was initially impaired, but improved over the first weeks of life. There was however a persistent renal wasting of magnesium. Her craniofacial appearance with infraorbital creases and low set dysplastic ears was similar to the brothers' described by Hisama et al. [1998; Am J Med Genet 80:335-342]. She had choanal atresia, athelia, a preauricular pit, gingival cysts, broad digits with small nails, right aortic arch with a vascular ring, hypothyroidism, impaired glucose homeostasis, hypoadrenalism, neurological impairment, and brain calcifications on CT. She died after 13 weeks of intensive care. Her mother as a child and maternal grandfather as an adult had neck cysts removed. The similarities between the cases suggest a common syndrome.

Methimazole embryopathy: A contribution to defining the phenotype

It has been suggested that children prenatally exposed to methimazole may present some features in common but the phenotype remains to be defined. The reported facial features include upward slanted palpebral fissures, arched flared eyebrows and small nose with a broad bridge. Choanal atresia and other anomalies like esophageal atresia and aplasia cutis were also described with this embryopathy. Additionally, developmental delay was reported in some patients along with one of these major malformation. We present a patient with the mentioned facial features, developmental delay and radio-ulnar synostosis whose mother has been exposed to methimazole during pregnancy and any other ethiological cause could be recognize.

Bipolar affective disorder associated with 11q24.2 disruption—A second report

A recent report identified bipolar affective disorder in a patient with a de novo deletion 11q24.2. We record a further instance involving this cytogenetic region and bipolar affective disorder in a patient with a balanced translocation.

Management of bilateral choanal atresia in a foal

CASE DESCRIPTION

A 1-day-old Standardbred foal with a history of extreme respiratory distress after birth consistent with upper airway obstruction was evaluated. A temporary tracheostomy tube was placed by the referring veterinarian.

CLINICAL FINDINGS

On initial examination, there was evidence of hypoxic-ischemic syndrome, secondary to perinatal asphyxia. Endoscopy revealed obstruction of both nares at the level of the choanae; a diagnosis of bilateral choanal atresia was made.

TREATMENT AND OUTCOME

The foal was anesthetized and underwent transendoscopic laser fenestration of the buccopharyngeal membranes. Three weeks after surgery, cicatricial narrowing of the choanae was apparent and further transendoscopic ablation was performed. Recurrent stenosis necessitated revision surgeries involving a combination of laser ablation with topical administration of mitomycin and, subsequently, a combination of radial incisions into the stenotic tissue and repeated bougienage with a cuffed endotracheal tube. The degree of stenosis decreased, and at 1 year of age, the horse was an appropriate size for its age, had choanae that were almost maximally open (> 85%), and had entered training. Mild stenosis was still evident when the horse was reexamined the following year, although there was no evidence of exercise intolerance or respiratory compromise.

CLINICAL RELEVANCE

Bilateral choanal atresia in a foal can be successfully treated via transendoscopic fenestration of the buccopharyngeal membranes, enabling the horse to subsequently participate in athletic activities. Secondary problems resulting from initial asphyxia and recurrent stenosis at the surgical site can be overcome but may require prolonged and extensive treatment.

Carbimazole embryopathy: An emerging phenotype

Concerns about the safety of carbimazole in pregnancy were raised in 1985. Since this time many reports of children believed to have been affected by carbimazole in utero have appeared in the medical literature. Initial reports were of an increased incidence of scalp defects in the infants of treated mothers, but many other anomalies have now been described. Choanal atresia, gastrointestinal anomalies-particularly esophageal atresia, athelia/hypothelia, developmental delay, hearing loss, and dysmorphic facial features have all been reported. The phenotype associated with exposure to carbimazole appears to be rare but specific with distinctive facial features. We report on two new cases of carbimazole embryopathy with strikingly similar facial features.

Hypothelia, syndactyly, and ear malformation?a variant of the scalp-ear-nipple syndrome?: Case report and review of the literature

The scalp-ear-nipple syndrome is a rare autosomal dominant condition that involves lesions of the scalp, malformed external ears, and absence of rudimentary nipples and breasts. We report a case of a woman with hypothelia, bilateral mildly malformed ears, and syndactyly of the hands and feet, and review the literature on the hypothelia/athelia phenotype. This case may represent a mild phenotype of the scalp-ear-nipple syndrome or a newly recognized entity.

Aplasia cutis congenita after methimazole exposure in utero

We describe a patient who was exposed to the antithyroid drug methimazole during the first 6 weeks of gestation and was born prematurely with scalp and skull defects associated with facial asymmetry. A review of the literature seems to support the hypothesis that methimazole is a potential teratogen. Although the risk of birth defects is low with clinically applied doses of the drug, it cannot be regarded as safe and should therefore be avoided in the treatment of pregnant women.

Choanal atresia associated with prenatal methimazole exposure: Three new patients

We report three patients with bilateral choanal atresia in children prenatally exposed to methimazole (MMI) in order to define a MMI embryopathy clinical pattern. The combination of choanal atresia and other specific malformations strongly resembles previously reported patients exposed to MMI in utero. At present, propylthiouracil is considered the best treatment in pregnancies. However in Argentina and some other countries MMI is the only antithyroid drug, possibly posing a significant risk to the unborn fetus.

Malformations following methimazole exposure in utero: An open issue

BACKGROUND

In hyperthyroidism-complicated pregnancies, medical therapy is necessary to reach an euthyroid condition, and propylthiouracil (PTU) or methimazole (MMI) are used. These drugs are equally effective, but may cause fetal and neonatal hypothyroidism because they freely cross the placenta. Although PTU has not been significantly associated with embryo-fetal anomalies, it has been suggested that MMI might be responsible for a specific embryopathy.

CASE(S)

Two cases of major congenital anomalies after MMI exposure during pregnancy are reported.

CONCLUSIONS

PTU should be the drug of choice, and the use of MMI should be restricted to cases with allergic reactions, intolerance, or poor response to PTU.

Choanal stenosis, hypothelia, deafness, recurrent dacryocystitis, neck fistulas, short stature, and microcephaly: report of a case

We report on a 11-year-old girl with bilateral choanal stenosis, hypothelia, hearing loss, recurrent dacryocystitis, neck fistulas, short stature, and microcephaly. Only three individuals with choanal atresia from a consanguineous family have been reported. One of the patients also had hypoplastic nipples, hypotonia, and delay in speech development. Similar clinical features were seen in two children reported by Greenberg [1987: Am J Med Genet 28:931-934] and Wilson et al. [1998: Am J Med Genet 75:220-222]. They were prenatally exposed to methimazole because of maternal Graves disease. Neck fistulas and microcephaly noted in our patient were not previously reported as features of the syndrome or in the patients prenataly exposed to methimazole. Our patient and those reported by Qazi et al. [1982: Am J Med Genet 13:413-416] most probably have a rare syndrome characterized by this distinctive combination of symptoms. Prenatal exposure to methimazole can cause a phenocopy of the syndrome, which was probably the case in the patients reported by Greenberg and Wilson et al.

Choanal atresia: the result of maternal thyrotoxicosis or fetal carbimazole?

We present the fourth published case of a child affected with choanal atresia following maternal treatment with carbimazole. The mother was receiving her highest dose of carbimazole at the crucial period for development of the choanae, between days 35 and 38.

Drug-induced congenital defects: strategies to reduce the incidence

Approximately 1% of congenital anomalies relate to pharmacological exposure and are. in theory, preventable. Prevention consists of controlled administration of drugs known to have teratogenic properties (e.g. retinoids, thalidomide). When possible, prevention could take the form of the use of alternative pharmacological therapies during the pre-conception period for certain specific pathologies, selecting the most appropriate agent for use during pregnancy [e.g. haloperidol or a tricyclic antidepressant instead of lithium; anticonvulsant drug monotherapy in place of multitherapy; propylthiouracil instead of thiamazole (methimazole)], and substitution with the most suitable therapy during pregnancy (e.g. insulin in place of oral antidiabetics; heparin in place of oral anticoagulants; alpha-methyldopa instead of ACE inhibitors). Another strategy is the administration of drugs during pregnancy taking into account the pharmacological effects in relation to the gestation period (e.g. avoidance of chemotherapy during the first trimester, avoidance of nonsteroidal anti-inflammatory drugs in the third trimester, and avoidance of high doses of benzodiazepines in the period imminent to prepartum).

An autosomal recessive syndrome of choanal atresia, hypothelia/athelia and thyroid gland anomalies overlapping bamforth syndrome, ANOTHER syndrome and methimazole embryopathy

Two sibs from an inbred Arab family are described with an autosomal syndrome of choanal atresia, hypothelia/athelia and thyroid gland anomalies overlapping Bamforth syndrome, ANOTHER syndrome and methimazole embryopathy. In one case the syndrome described was lethal. Cases with similar features are reviewed and genetic mutations discussed.

Update on new developments in the study of human teratogens

BACKGROUND AND METHODS

The purpose of this annual article is to highlight and briefly review new and significant information on agents that may be teratogenic in pregnant women. Various sources of on-line and printed information are given.

RESULTS

The following topics have been discussed: 1) lithium medication: decreased estimate of risk; 2) cigarette smoking and genotype as contributors to oral-facial clefts and clubfoot; 3) trimethoprim; 4) methimazole syndrome?; 5) glucocorticoids and oral-facial clefts; 6) binge drinking; 7) fetal valproate syndrome; and 8) carbamazepine.

CONCLUSIONS

We have highlighted several maternal exposures during pregnancy that are associated with small but increased rates of birth defects, generally only a few cases per 1,000 infants. These exposures include cigarette smoking, and treatment with lithium, trimethoprim, methimazole, or corticosteroids. This weak teratogenic effect was usually identified by the linkage of an uncommon treatment with an unusual birth defect outcome. The use of modern epidemiologic techniques, especially prospective multicenter studies that provide increased numbers, has helped to strengthen the evidence for these associations. We discuss how teratogenic risks that are small in comparison to the background risk can be presented to at-risk women and their doctors. We have briefly listed some elements that might be used in prioritizing further studies of suspected teratogenic exposures. Various existing methods for expressing the strength of evidence for human teratogenicity are also given.

Extrathyroidal actions of antithyroid thionamides

Some compounds having thionamide structure inhibit thyroid functions. Such antithyroid thionamides include mercaptomethylimidazole (methimazole), thiourea and propylthiouracil, of which mercaptomethylimidazole is widely used to treat hyperthyroidism. Undesirable side effects develop from these drugs due to extrathyroidal actions. Antithyroid thionamides inhibit lactoperoxidase which contributes to the antibacterial activities of a number of mammalian exocrine gland secretions that protect a variety of mucosal surfaces. These drugs stimulate both gastric acid and pepsinogen secretions, thereby augmenting the severity of gastric ulcers and preventing wound healing. Increased gastric acid secretion is partially due to the H2 receptor activation, and also through the stimulation of the parietal cell by intracellular generation of H2O2 following inactivation of the gastric peroxidase-catalase system. Severe abnormalities may develop in blood cells and the immune system after thionamide therapy. It causes agranulocytosis, aplastic anemia, and purpura along with immune suppression. Olfactory and auditory systems are also affected by these drugs. Thionamide affects the sense of smell and taste and also causes loss of hearing. It binds to the Bowman's glands in the olfactory mucosa and causes extensive lesion in the olfactory mucosa. Thionamides also affect gene expression and modulate the functions of some cell types. A brief account of the chemistry and metabolism of antithyroid thionamides, along with their biological actions are presented.

Adverse effects of prenatal methimazole exposure

BACKGROUND

A specific phenotype of methimazole (MMI) induced malformations has recently been postulated. MMI embryopathy is characterized by minor dysmorphic features, choanal atresia and/or esophageal atresia, growth retardation, and developmental delay.

METHODS

We prospectively studied the outcome of pregnancy in 241 women counseled by 10 Teratology Information Services (TIS) of the European Network of Teratology Information Services (ENTIS) because of MMI exposure, and compared them with those of 1,089 pregnant women referred to TIS because of exposure to nonteratogenic drugs (control group). Information was obtained by mail or telephone interview.

RESULTS

There was no increase in the general rate of major anomalies or of spontaneous or induced abortions in the MMI-exposed group in comparison with the control group. Two newborns were affected with one of the major malformations that are part of the postulated embryopathy.

CONCLUSIONS

The results of this study indicate that choanal as well as esophageal atresia may have a higher incidence than expected in fetuses exposed to MMI between 3 and 7 gestational weeks. Until further data are available, thyrotoxicosis should be treated with propylthiouracil, as it is apparently safer for use during the fertile period.

Imaging studies in the diagnostic workup of neonatal nasal obstruction

Twelve neonates presenting with nasal obstruction after birth were evaluated by imaging studies for diagnostic reasons. Four groups were recognized: Group I: choanal atresia (n = 5) and choanal stenosis (n = 1); Group II: congenital nasal pyriform aperture stenosis (CNPAS) (n = 3) and holoprosencephaly (n = 1); Group III: nasolacrimal duct mucocele (n = 1); Group IV: nasal hypoplasia (n = 1). Associated anomalies were found in eight patients. Four patients with choanal atresia showed manifestations of the CHARGE (coloboma, congenital heart defect, atretic choanae, retarded physical and neuromotor development associated with central nervous system anomalies, genital hypoplasia, and ear anomaly and/or deafness) association. In the fifth patient with choanal atresia, the diagnosis of amnion disruption sequence was made. One patient with CNPAS had a solitary maxillary central incisor (SMCI), a mild form of holoprosencephaly. Besides proboscis and synophthalmos, SMCI was also present in the holoprosencephaly case. The patient with severe nasal hypoplasia had warfarin embryopathy. This review emphasizes the need for performing imaging studies in the diagnostic workup of neonates born with nasal obstruction.

Maternal issues affecting the fetus

Maternal disorders and exposures that affect fetal cardiac structure and function are reviewed, emphasizing fetal echocardiographic diagnosis and monitoring, and approaches for in utero therapy. Maternal diabetes, hyperthyroidism, lupus erythematosis, epilepsy, congenital heart disease, infections, and drug exposures are considered.

Fetal and neonatal hyperthyroidism

Fetal and neonatal hyperthyroidism are usually produced by transplacental passage of thyroid-stimulating immunoglobulins. Most commonly, the thyroid-stimulating immunoglobulins are a component of active maternal Graves' disease. However, such antibodies may continue to be produced after ablation of the thyroid by surgery, radioiodine, or by the immune mechanisms of Hashimoto's thyroiditis. Other mechanisms that have produced fetal and neonatal hyperthyroidism include activating mutations of the stimulatory G protein in McCune-Albright syndrome and activating mutations of the thyrotropin (TSH) receptor. Fetal hyperthyroidism may be associated with intrauterine growth retardation, nonimmune fetal hydrops, craniosynostosis, and intrauterine death. Features of this condition in the neonate include hyperkinesis, diarrhea, poor weight gain, vomiting, ophthalmopathy, cardiac failure and arrhythmias, systemic and pulmonary hypertension, hepatosplenomegaly, jaundice, hyperviscosity syndrome, thrombocytopenia, and craniosynostosis. The time course of thyrotoxicosis depends on etiology. Remission by 20 weeks is most common in neonatal Graves' disease; remission by 48 weeks is nearly always seen. A subset of these patients may have persistent disease when there is a strong family history of Graves' diseases. Disease persistence is characteristic of patients with activating mutations of the TSH receptor. Treatment of fetal hyperthyroidism comprises administration of antithyroid drugs to the mother. Fetal heart rate and fetal growth should be monitored. Ultrasonography may reveal changes in thyroid size. At times, cordocentesis may be useful for monitoring fetal thyroid function. Hyperthyroid neonates may be treated with antithyroid drugs, beta-adrenergic receptor blocking agents, iodine, or iodinated contrast agents, and at times, with glucocorticoids and digoxin. Nonremitting causes of neonatal hyperthyroidism require ablative treatments such as thyroidectomy.