Original ArticlesMelorheostosis A Clinical, Pathologic, and Radiologic Case SeriesFick, Cameron N. MS*; Fratzl-Zelman, Nadja PhD†; Roschger, Paul PhD†; Klaushofer, Klaus MD†; Jha, Smita MD‡; Marini, Joan C. MD, PhD§; Bhattacharyya, Timothy MD* Author Information *Clinical and Investigative Orthopedics Surgery Unit, National Institute of Arthritis and Musculoskeletal and Skin Diseases ‡Section on Congenital Disorders, Clinical Center §Section on Heritable Disorders of Bone and Extracellular Matrix, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD †Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of WGKK, and AUVA Trauma Center Meidling, 1st Medical Department Hanusch Hospital, Vienna, Austria Conflicts of Interest and Source of Funding: Supported by the Division of Intramural Research of the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the Austrian Workers’ Compensation Board/Austrian Social Insurance for Occupational Risks (AUVA), and the Vienna Regional Health Insurance Fund (WGKK). C.N.F. acknowledges funding support through the National Institutes of Health (NIH) Medical Research Scholars Program, a public-private partnership supported jointly by the NIH and generous contributions from the Doris Duke Charitable Foundation, Genentech, American Association for Dental Research, the Colgate-Palmolive Company, Elsevier, and other private donors. The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Timothy Bhattacharyya, MD, Clinical and Investigative Orthopedics Surgery Unit, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Building 10-CRC, Room 4-2339, Bethesda, MD 20892-3675 (e-mail: [email protected]). The American Journal of Surgical Pathology 43(11):p 1554-1559, November 2019. | DOI: 10.1097/PAS.0000000000001310 Buy Metrics Abstract Melorheostosis is a rare sclerosing bone disease characterized by excessive cortical bone deposition that is frequently on the differential diagnosis for bone biopsies. Although the radiologic pattern of “dripping candle wax” is well known, the pathologic findings have been poorly defined. Here, we comprehensively describe the histology of melorheostosis in 15 patients who underwent bone biopsies. Common histologic findings included: dense cortical bone (73.3%), woven bone (60%), and hypervascular features and increased porosity (66.7%). One third of the patients (5/15) also had prominent cement lines. Multiple patients had >1 histologic pattern (ie, dense cortical bone and hypervascularity). Overall, this study suggests that melorheostosis exists with several histologically distinct patterns. When confronted with a case of suspected melorheostosis, the clinical pathologist should use the histologic features common to melorheostotic lesions presented here in conjunction with the patient’s clinical presentation and radiographic findings to arrive at a diagnosis. An illustrative case is presented. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.