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Living with Acalvaria

An extremely rare condition present at birth in which the flat bones of the skull are missing.

Understanding Acalvaria

Acalvaria is an extremely rare malformation in which the flat skull bones, the dura mater, and scalp muscles are absent.

The base of the skull and the face are fully formed and usually look normal. A layer of skin covers the brain, and the brain's hemispheres look normal. This helps tell it apart from anencephaly. GARD lists onset as during pregnancy and as a newborn.

Signs & symptoms

Symptoms vary from person to person. GARD lists these among the most common:

  • Missing skull bones (cranial defect)
  • Brain development differences
  • Small or absent cerebellum
  • Extra little finger

Not everyone has every symptom. GARD's list comes from the Human Phenotype Ontology.

Diagnosis

  1. Talk with your doctor

    Share the symptoms you've noticed, when they started and your family health history. Notes and photos can help.

  2. See a specialist

    Specialists who may be involved include bone and joint specialists.

  3. Ask which tests can help

    Your care team will decide which exams and tests can confirm the diagnosis.

Care & treatment

Care team
Bone and joint specialists (orthopedists or orthopedic surgeons)
Expert care
Ask about multidisciplinary care centers for rare conditions
Treatment
GARD doesn't list specific treatments for this condition. Your care team will tailor care to your symptoms.
Research
Clinical trials and observational studies may be options. See the research section below.

General information, not medical advice. Your care team makes the decisions.

Everyday life

Living with a rare condition is easier with support.

  • Connect with rare disease patient organizations for support
  • Keep notes on symptoms, changes and questions for appointments
  • Ask about patient registries that help research
  • Look into financial aid and travel resources for care visits
Bring these questions to your next doctor visit
What does imaging show about my baby's brain?
Which specialists should be involved in care?
Are other body systems affected that we should check?

Quick facts

Symptoms usually startduring Pregnancy and as a Newborn

The cause of acalvaria is still unknown.

Also known as: absent bone maturation of skullcap; absent ossification of calvaria; absent ossification of skull vault; acrania; primary acalvaria

Patient organizations

Rare-disease groups that can help

Source: NIH GARD · AcalvariaGARD ID 361 · GARD page updated September 2026 · Plain-language summary by Know Rare; editorial review pending. General information, not medical advice.

You are more than your diagnosis

Perspectives from people navigating life with Acalvaria.

Explore the Acalvaria blog

Explore research for Acalvaria

Explore actively recruiting Acalvaria studies with HealthSpark.

HealthSpark

Find actively recruiting studies for Acalvaria with HealthSpark. Share your city to explore research near you.

  • Recruiting studies from ClinicalTrials.gov
  • Share your city to look for research near you
  • Eligibility is confirmed by the study team

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Powered by HealthSpark, our AI chat helper · Study information from ClinicalTrials.gov · Eligibility is confirmed by the study team.

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