Ectodermal abnormalities associated with methimazole intrauterine exposure

Neural Tube Defects and Associated Anomalies before and after Folic Acid Fortification

OBJECTIVE

To examine the prevalence and types of neural tube defects and the types of anomalies co-occurring with neural tube defects in 6 years before fortification of cereal grain flour with folic acid (1992-1998) and 20 years after fortification (1999-2018) in South Carolina, a state with a historically high prevalence of these birth defects.

STUDY DESIGN

The prevalence of neural tube defects was determined by active and passive surveillance methods in South Carolina since 1992. The types of neural tube defects and co-occurring malformations were determined by prenatal ultrasound and post-delivery examination.

RESULTS

In the 6 prefortification years, 363 neural tube defects were identified among 279 163 live births and fetal deaths (1/769), 305 (84%) of which were isolated defects of the calvaria or spine. In the 20 fortification years, there were significant reductions in the prevalence and percentage of isolated defects: 938 neural tube defects were identified among 1 165 134 live births and fetal deaths (1/1242), 696 (74.2%) of which were isolated. The current prevalence of neural tube defects in South Carolina (0.56/1000 live births and fetal deaths) is comparable with that nationwide.

CONCLUSIONS

The continued occurrence of neural tube defects, the majority of which are isolated, after folic acid fortification of cereal grain flours suggests that additional prevention measures are necessary to reduce further the prevalence of these serious defects of the brain and spine.

Teratogen update: Antithyroid medications

OBJECTIVE

Thyroid disorders including hyperthyroidism are common during pregnancy. Untreated hyperthyroidism can result in adverse outcomes for pregnancy.

METHODS

Iodine, propylthiouracil (PTU), carbimazole (CMZ), and methimazole (MMI) are common medications for hyperthyroidism treatment. The literature regarding antithyroid medication use in pregnancy and breastfeeding is reviewed.

RESULTS

Animal studies for PTU have suggested congenital anomalies while animal studies for MMI have only indicated adverse outcomes at higher doses than used in humans. Epidemiological studies have noted an increased risk of congenital anomalies for PTU less often than CMZ or MMI but the epidemiological evidence remains mixed. A pattern of anomalies has been described for CMZ and MMI, from both case and epidemiological studies, including choanal atresia, aplasia cutis congenita, and other facial, heart, gastrointestinal, and skin anomalies. Closer examination of cases indicates that a few cases of the anomalies have occurred without exposure to CMZ or MMI and outside of the proposed critical period. PTU has a small risk of hepatotoxicity which rarely results in liver transplantation and death. Some authors have suggested that PTU be prescribed in early pregnancy and switched to MMI in late pregnancy. Untreated hyperthyroidism, from either a lack of medications or switching medications during the first trimester, may also increase the chance of congenital anomalies. Multiple case studies and larger epidemiological studies have failed to provide clear, consistent outcomes for the use of PTU, CMZ, and MMI in pregnancy. MMI and PTU both enter the breastmilk in small amounts.

CONCLUSION

Additional research is needed to assist in the medical management and exposure counseling of pregnant and breastfeeding women with hyperthyroidism.

[Aplasia cutis congenita and antithyroid drugs during pregnancy: Case series and literature review]

BACKGROUND

Aplasia cutis congenita (ACC) following in utero exposure to antithyroid drugs such as methimazole/carbimazole (MTZ/CMZ) has been reported since 1972. Though currently included in MTZ/CMZ embryopathy, it remains poorly characterized and is little discussed. Having seen two cases within a short period of time, we carried out a literature review and searched the French pharmacovigilance database for notification of cases.

PATIENTS AND METHODS

We performed a search of the literature in the Medline database using the following keywords: "aplasia cutis congenita", "birth skin defects", "pregnancy" and "drug". All articles reporting cases of ACC following in utero exposure to antithyroid drugs were included. All cases of ACC under antithyroid drugs reported to French pharmacovigilance centres were analysed.

RESULTS

Three hundred and sixty-eight articles were retrieved and 31 were analysed, including a further 4, mentioned in selected articles, giving 59 cases of ACC under MTZ/CMZ reported in the literature and having an intrinsic accountability score of plausible or dubious. ACC was typically isolated, single, small in size, and localised on the median scalp area. Exposure occurred in the first weeks of gestation. There were 6 familial cases involving siblings. Ten ACC and MTZ/CMZ cases were reported to pharmacovigilance centres in France.

DISCUSSION

Practitioners should be aware of ACC following MTZ/CMZ exposure in utero, whether it occurs in isolation or not. It is likely a teratogenic effect of MTZ/CMZ enhanced by a genetic predisposition.

Aplasia cutis congenita and other anomalies associated with methimazole exposure during pregnancy

Aplasia cutis congenita (ACC) is a congenital defect consisting of a circumscribed absence of skin that usually involves the scalp. The etiology is uncertain, and several teratogenic agents such as methimazole have been involved. We report two cases of ACC and other anomalies in newborns exposed to methimazole during pregnancy.

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.

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.

Aplasia cutis congenita with skull defect in a monozygotic twin after exposure to methimazole in utero

BACKGROUND

Aplasia cutis congenita (ACC) is a condition in which localized or widespread areas of skin are absent at birth. Defective lesions show complete absence of all layers of skin, occasionally extending to skull or dura. ACC is etiologically heterogeneous; many different etiologies including teratogens have been documented.

CASE

We describe the first reported case of a monozygotic twin with ACC after exposure to methimazole in utero. The female patient was born at 36 weeks gestation as the first child of monozygotic twins. The mother received methimazole between the 11th and 17th weeks of pregnancy because of transient hyperthyroidism. The second child did not have ACC. The patient had defects of the scalp, skull, and dura (7 x 5 cm) on the sagittal line of the parieto-occipital region. No other malformations were noted. The scalp defect has been treated daily with sterile physiological saline and petrolatum dressing in addition to intravenous antibiotics. Trafermin, a recombinant human fibroblast growth factor, was sprayed from day 6 to promote epithelialization of the scalp defect. On day 21, she had high fever due to infection of the defect lesion, which was controlled by povidone iodine dressing and intravenous antibiotics. The defect of the scalp was well healed after 6 weeks, but the skull defect remained unclosed.

CONCLUSIONS

We describe a rare case of a monozygotic twin with ACC and skull defect after methimazole exposure in utero. The findings of our case suggest that methimazole is a potential teratogen of ACC.

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.

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.

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.

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.