Pili annulati, also known as ringed hair, is a rare hair shaft abnormality that manifests as alternating light and dark banding and a speckled appearance of scalp hair. The lighter banding occurs due to clusters of abnormal air-filled cavities in the cortex of the hair shaft. Some patients report easy breakage and abnormal weathering.
Pili annulati may be acquired but is most commonly inherited in an autosomal dominant pattern. The age of onset is usually 2 years. It is a lifelong condition.
ICD10CM: Q84.1 – Congenital morphological disturbances of hair, not elsewhere classified
SNOMEDCT: 21926007 – Pili annulati
Differential Diagnosis & Pitfalls
Pseudopili annulati – Likely a variant of pili annulati. Patients present with banding on their hairs due to optical effects from twisted hair. On light microscopy, there are no air-filled bands.