Rare diseases · Sign or symptom
Delayed pneumatization of the mastoid process
HP:0005906
What it means
An abnormally reduced degree of pneumatization (i.e., formation of air cells) in the mastoid process with respect to age-dependent norms.
Rare diseases that can present with this1
The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Mastoid processes poorly pneumatized
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Start free with EleplanThis page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.