Considering the changes in moral principles, human behavior and behavioral values through the ages, in Egill Skallagrímsson's Saga, Egill presents us with altered mental status. This is in terms of what at present is considered symptoms of an anti-social personality, and bipolar affective disorder. Egill Skallagrímsson is considered one of the most famous Vikings in the Icelandic Sagas. Archaeological findings mentioned in Egill's Saga indicate disfigurement of his skull, which has led many authors to suggest that Egill suffered from skeletal dysplasia. The primary assumption in the literature is that Egill Skallagrímsson was affected by Paget's disease of bone. This consideration is additionally based on the scholar's interpretation of the Saga text. The unique storytelling style in the Saga of Egill Skallagrímsson is evident; however, the question of the story's truthfulness remains open. In this article, we investigate Egill Skallagrímsson's assumed Paget's disease of bone, based on the physical and mental symptoms disclosed in the Saga of Egill Skallagrímsson. Associated with the assumption, the author's hermeneutics of Egill's Saga in the context of modern-day knowledge of Paget's disease of bone, brings forward the probability estimate to the range of permille. In Scandinavian folklore and mythology, a tale by Saxo Grammaticus of a notorious shield-maiden named Visna, reminds of Egill, as noted by Snorri Sturluson. Hence, in reference to Egill Skallagrímsson's mental status and physical appearance as listed in Egill's Saga, the authors recommend the name for his condition to be “Visna of Egill Skallagrímsson”.

Figure I. Sculpture by professor Magnús H. Ágústsson MD and sculptor, Kingston, NY, USA. This original fine art sculpture and work by Dr. Ágústsson was given by the artist to the national library of Iceland, the 6^th of April in 2000. It represents the interpretation of the sculptor according to the portrayal of Egill Skallagrímsson listed in the Old Norse “Egill's Saga”.

Figure II. The Paget's disease of bone macroscopic characteristics include irregular bone surface and bone deformity, in addition to thickened cortex and increased caliber of trabecular bone (diploë) compared to healthy bone tissue. Thickening of the calvarium (A) and the skull base (B) caused by Paget's disease of bone results in compression af neurovascular foramina. Case courtesy of professor Thomas Schnalke and Christoph Weber, Berlin Museum of Medical History at the Charité, Germany.

Figure III. Sagittal and axial Computed Tomography scans showing cranial bone-images without radiocontrast. Paget's disease of bone (A and B) with Tam o' shanter sign and cotton wool appearance in the diploë area (white arrows, case courtesy of professor Frank Gaillard, Radiopaedia.org, rID: 2639). Healthy calvarium (C-D) by comparison is shown at the right (case courtesy of department of radiology, Randers Central Hospital, Denmark). Since the skull's cortical bone consists of fused shells, it is appropriate to quote the description in Egill's Saga when Skapti the Priest Thorarinsson handled the skull of Egil. According to the Old Norse “Egill's Saga” the skull was found wondrously large, extremely heavy and furthermore all wave-marked on the surface like a scallop shell.

Figure IV. Confocal imaging (A) of in vitro Cell Tracker Green and 4′,6-diamidino-2-phenylindole (DAPI) stained multinucleated giant cell/ osteoclast (white arrow). Enhanced osteoclastic activity with increased secreation of osteolytic enzymes is the primary cause of abnormal bone turnover and bone resorption in Paget's disease of bone (osteolytic phase). Increased bone resorption (B-C) with lacunae formations (C). This stage leads to the production af paracrine factors, triggering the cascade of reactions within osteoblasts causing the mixed phase of the disease, which in its final stage represents the abnormal osteoslerotic phase.

Figure V. Light microscopy image (A) showing Masson Goldner stained trabecular Paget‘s diseased bone, with intertrabecular fibrosis, high vascularity, and focal T cell accumulation (10x). Higher magnifcation reveals profound lacunae and increased recruitment of multinucleated giant cells/ osteoclasts. From the right, trabecular bone is shown with increased formation of osteoid at the surface (white arrow, case courtesy of Dr. Björn Jobke, Radiopaedia.org, rID: 39303). At the bottom left a TRAP (tartrate-resistant acid phosphatase) positive cell and the phenotype of osteoclast (B, scale bar 20 µm). Paramyxoviridae-inclusion bodies have been found within pre-cursor cells of osteoclasts and in osteoclasts of Page‘s disease of bone, suggesting viral induced pathogenesis of the disease. These findings are controversial and the exact etiology of the disease is unknown. Scanning electron microscopy imaging (C) after the fusion of multiple osteoclastic precursor cells, showing cell attachment, formation of ruffled border, and the edge of resorption lacunae.