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Disease Profile


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)

Primary acalvaria


Congenital and Genetic Diseases


Primary acalvaria is an extremely rare malformation characterized by the absence of the flat skull bones of the brain, dura mater, and scalp muscles. The skull base and facial features are fully formed and usually appear normal.[1][2][3] The cause of acalvaria is still unknown.[1] Acalvaria can be distinguished from anencephaly, the most common differential diagnosis, by the presence of a layer of skin overlying the brain matter and normal cerebral hemispheres. [1] This malformation is most often lethal at birth due to other associated anomalies or to trauma during delivery, but a few surviving infants have been reported.[2] Prenatal diagnosis via transvaginal ultrasound and/or magnetic resonance imaging is critical for better pregnancy management. The initial treatment is conservative, mainly aimed at supportive care and management of any associated anomalies, if present. [1] Infants with acalvaria are managed conservatively in the newborn period because spontaneous bone growth has been seen in some newborns with other skull abnormalities, such as aplasia cutis congenita. Skull reconstruction by bone grafting and cranioplasty at school age has been discussed in the literature. [1][4]


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
Aplasia/Hypoplasia of the cerebellum
Absent/small cerebellum
Absent/underdeveloped cerebellum

[ more ]

30%-79% of people have these symptoms
Abnormality of neuronal migration
Calvarial skull defect
Cranial defect
Skull defect

[ more ]

Postaxial hand polydactyly
Extra little finger
Extra pinkie finger
Extra pinky finger

[ more ]

5%-29% of people have these symptoms
Abnormal lung lobation
Abnormality of cardiovascular system morphology
Cleft palate
Cleft roof of mouth
Too much cerebrospinal fluid in the brain
Wide-set eyes
Widely spaced eyes

[ more ]

Spina bifida
Percent of people who have these symptoms is not available through HPO
Autosomal recessive inheritance
Congenital onset
Symptoms present at birth

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.

In-Depth Information

  • 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.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • 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 Acalvaria. Click on the link to view a sample search on this topic.


  1. Gupta, V and Kumar, S.. Acalvaria: A rare congenital malformation. Journal of Pediatric Neuroscience. Sep Dec 2012;
  2. Acalvaria. Orphanet. March 2006; https://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=945. Accessed 9/19/2013.
  3. Harris, C.. Acalvaria: A Unique Congenital Anomaly. American Journal of Medical Genetics. 1993;
  4. Khadilkar, VV., et.al.. Acalvaria. Indian Pediatrics. 2004;