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Disease Profile

Fetal hydantoin syndrome

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Dilantin Embryopathy; Phenytoin Embryopathy


Congenital and Genetic Diseases; Ear, Nose, and Throat Diseases; Mouth Diseases


Fetal hydantoin syndrome is a disorder that is caused by exposure of a fetus to phenytoin, a drug commonly prescribed for epilepsy. Not all infants exposed to phenytoin will be affected with the disorder. Symptoms in affected individuals may include abnormalities of the skull and facial features, growth deficiencies, underdeveloped nails of the fingers and toes, and/or mild developmental delays. Other findings occasionally associated with this syndrome include cleft lip and palate, having an abnormally small head (microcephaly) and brain malformations with more significant developmental delays.[1] Treatment may include surgery for cleft lip and palate and special education and related services for children with learning delays. Other treatment is symptomatic and supportive.[1]


There is a wide range in the nature and severity of characteristics associated with fetal hydantoin syndrome. Of infants born to women who used phenytoin during pregnancy, 10-30% are reported to show some of the characteristics associated with this syndrome. Few infants exposed only to phenytoin have all of the characteristic that have been reported.[2]

Children with this condition may be small at birth, with increased hair on the body and face, and with poorly developed fingernails and toenails.[1] They may also have poor muscle tone.[1] Facial features that may be present with this syndrome include a flat bridge of the nose; an underdeveloped vertical groove in the center of the upper lip (philtrum); a large mouth; and malformed ears. Features specific to the eyes may include down-slanted eyes; widely spaced eyes (hypertelorism); crossed eyes (strabismus); drooping eyelids (ptosis); and/or epicanthal folds (skin folds of the eyelid covering the inner corner of the eye). Other features that have been reported include a short or webbed neck and low-set hair line.[1][3] Growth deficiencies may include underdeveloped fingers and/or toes, malformed nails, as well as finger-like thumbs.[1]

These features are often associated with growth delay and varying degrees of developmental delay. The risk for an affected child to be neurologically impaired is estimated at 1 to 11 % (two to three times higher than for the general population). The risk of cleft lip and/or palate and heart defects is estimated to be about five times higher among exposed infants. Some case reports have suggested an increased risk for the occurrence of benign (noncancerous) or malignant (cancerous) tumors, such as neuroblastoma or other neonatal tumors (ependymoma, ectodermal tumors, Wilms tumor).[3]

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Abnormal dermatoglyphics
Abnormal fingerprints
Abnormality of the pinna
Abnormally shaped ears
Auricular malformation
Deformed ears
Malformed ears

[ more ]

Depressed nasal ridge
Flat nose
Recessed nasal ridge

[ more ]

Hearing abnormality
Abnormal hearing
Low-set, posteriorly rotated ears
Short nose
Decreased length of nose
Shortened nose

[ more ]

30%-79% of people have these symptoms
Abnormality of the fontanelles or cranial sutures
Bifid scrotum
Cleft of scrotum
Coarse hair
Coarse hair texture
Eye folds
Prominent eye folds

[ more ]

Everted lower lip vermilion
Drooping lower lip
Outward turned lower lip

[ more ]

Global developmental delay
Wide-set eyes
Widely spaced eyes

[ more ]

Hypoplastic fingernail
Small fingernail
Underdeveloped fingernail

[ more ]

Intrauterine growth retardation
Prenatal growth deficiency
Prenatal growth retardation

[ more ]

Low posterior hairline
Low hairline at back of neck
Abnormally small skull
Decreased circumference of cranium
Decreased size of skull
Reduced head circumference
Small head circumference

[ more ]

Drooping upper eyelid
Short distal phalanx of finger
Short outermost finger bone
Short stature
Decreased body height
Small stature

[ more ]

Squint eyes

[ more ]

Thickened nuchal skin fold
Thickened skin folds of neck
Thickened skin over the neck

[ more ]

Triphalangeal thumb
Finger-like thumb
Wide intermamillary distance
Wide-spaced nipples
Widely spaced nipples
Widely-spaced nipples

[ more ]

Wide mouth
Broad mouth
Large mouth

[ more ]

5%-29% of people have these symptoms
Abnormality of the cardiovascular system
Cardiovascular abnormality
Cleft palate
Cleft roof of mouth
Undescended testes
Undescended testis

[ more ]



Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Organizations Providing General Support

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

      • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

        In-Depth Information

        • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Fetal hydantoin syndrome. Click on the link to view a sample search on this topic.


          1. Fetal Hydantoin Syndrome. NORD. April 25, 2008; https://www.rarediseases.org/rare-disease-information/rare-diseases/byID/948/viewAbstract. Accessed 8/9/2011.
          2. Aaron B Caughey. Seizure Disorders in Pregnancy. eMedicine. June 28, 2011; https://emedicine.medscape.com/article/272050-overview#aw2aab6b3. Accessed 8/10/2011.
          3. E. Robert-Gnansia. Fetal hydantoin syndrome. Orphanet. February 2006; https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=1912. Accessed 8/10/2011.

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