Porotic hyperostosis (PH) is the expansion of the cranial diploë, generating 'hair-on-end' appearance on X-rays. This condition is extremely rare and had a prevalence of 0.08%. It is alternatively known as cribra orbitalia (CO) when the orbital roof is affected. In this study, we describe the gross morphology of two skulls affected by PH and CO. The first skull belonged to a 41-year-old female previously diagnosed with beta thalassemia. The skull was affected by excessive PH and CO. The second skull, belonging to a 35-year-old male diagnosed with unspecified thalassemia, showed PH without CO. The etiology of PH and CO is discussed. In conclusion, PH and CO are extremely rare, and are of significant importance for radiologists and anatomists when interpreting radiographs or encountering unusual gross morphology of the skull.
Keywords: Cribra orbitalia; Hair-on-end; Porotic hyperostosis; Thalassemia.