On the etiology and pathogenesis of porotic hyperostosis of the skull.

The 256 skulls and 66 skull fragments of the pre-Columbian Peruvian Indians in the Hrdlicka archeologic collection were examined for a porous bone lesion known as porotic hyperostosis. The age, sex, and geographic distribution, as well as the severity and pattern of involvement of the skull bones were noted in an attempt to define the etiology and the pathogenesis of the lesion. Porotic hyperostosis of the skull was present in 20% of the specimens and was probably caused by marrow expansion on the basis of iron deficiency. The lesion was more prevalent and severe among coastal dwellers; men and women were equally affected, and the parietal and occipital bones were the most frequently involved sites. Severe cases were observed only in infants and children, presumably because of limited marrow space and a special predilection for iron deficiency in infants, and of healing of the lesion in adults. Radiographic abnormalities included thinning of the outer table of the skull, diploic space widening, and a "hair-on-end" appearance. Sixty percent of all cases and 100% of severe cases demonstrated one or more of these findings.