Osteopoikilosis (OPK)

Discussion

Osteopoikilosis (osteopathia condensans disseminata) is a rare sclerosing bone dysplasia of unknown etiology. It is also known as Albers-Schonberg disease or by its Latin name, osteopathia condensans disseminata, which describes its main features. It is characterized by the presence of multiple and often symmetrical foci of dense spots in the spongious bone tissue or in the inner bone cortex. At histologic examination, these foci are found to be formed by dense trabeculae of spongious bone, sometimes forming a nidus without communication with bone marrow.¹

Osteopoikilosis is more commonly found in the epiphysis and metaphysis of the bones in upper and lower limbs, in the hand in carpal and metacarpal and in the foot in tarsal and metatarsal bones, while it is rarely seen in the pelvis, spine, ribs, and skull.¹

Typically, patients are asymptomatic, although 15% to 20% of patients may have mild articular pain and joint effusion. It is seen in both men and women and may occur at any age.^1,2 Several clinical abnormalities associated with OPK have been reported, including rheumatoid arthritis, synovial chondromatosis, and, more frequently, dermatological pathologies (such as dermatofibrosis lenticularis disseminata, keloid formations and scleroderma-like lesions).^2-5 In the case reported here, we did not observe any associated skeletal or organ anomalies. In the absence of any skeletal or dermatological changes, OPK has rarely been reported in the literature. Serowy⁶ could find only 100 reported cases in the literature since its initial description, and Borman et al⁷ found only 20 case reports in the past 50 years in the English literature.⁷

The radiological features of OPK are typical: multiple radiopaque round, oval, or lanceolate spots of uniform density that sometimes have a relatively clear central zone and are often symmetrical. These lesions can increase or decrease in size and number, or even disappear.^1-3

Radiologically, the differential diagnosis of OPK includes osteopathia striata, melorheostosis, tuberous sclerosis, sclerotic bone metastases, and osteoma (which may have similar clinical pictures but for which medical and orthopedic treatment may be necessary).^1,7

A radionuclide bone scan is essential in distinguishing OPK from primary bone tumors or osteoblastic bone metastases. Bone scan findings are usually normal in patients with OPK, but reveal slightly increased activity similar to the bone island or enostosis that reflects active osseous remodelling that may be detected, especially in young patients with classic radiographic findings that are consistent with OPK. An abnormal scan finding in an older patient should, however, be thoroughly investigated. A malignant transformation is also conceivable if the cellular activity exists in the foci of OPK.^3,8

Overlap syndromes, formerly known as mixed sclerosing dystrophies, in which OPK and other osteosclerotic bone disorders (such as fibrous dysplasia, osteopathia striata, and melorheostosis) are combined, must be borne in mind in the differential diagnosis. A combination of melorheostosis, OPK, and osteopathia striata (type I) is the most frequent among the other overlap syndromes.⁹

CONCLUSION

Although the natural course of this condition is benign and requires no treatment, the complications and coexisting pathologic conditions require medical attention. Therefore, it is important that an accurate diagnosis be made.

1. Resnick D, Niwayama G. Enostosis, hyperostosis, and periostitis. In: Resnick D, eds. Diagnosis of Bone and Joint Disorders. 3rd ed. Philadelphia, Pa: WB Saunders; 1995;4396-4466.
2. Benli IT, Akalin S, Boysan E, et al. Epidemiological, clinical and radiological aspects of osteopoikilosis. J Bone Joint Surg Br. 1992;74:504-506. Erratum in: J Bone Joint Surg Br. 1994;76:683.
3. Havitcioglu H, Gunal I, Gocen S. Synovial chondromatosis associated with osteopoikilosis-A case report. Acta Orthop Scand.1998;69:649-650.
4. Cazzola M, Caruso I, Montrone F, Sarzi Puttini P. Rheumatoid arthritis associated with osteopoikilosis: A case report. Clin Exp Rheumatol.1989;7:423-426.
5. Bicer A, Tursen U, Ozer C, et al. Coexistence of osteopoikilosis and discoid lupus erythematosus: a case report. Clin Rheumatol.2002; 21:405-407.
6. Serowy C. Dermatofibrosis lenticularis disseminata and osteopoikilosis [in German]. Arch Klin Exp Dermatol.1956;203:113-124.
7. Borman P, Ozoran K, Aydog S, Coskun S. Osteopoikilosis: Report of a clinical case and review of the literature. Joint Bone Spine. 2002;69:230-233.
8. Mungovan JA, Tung GA, Lambiase RE, et al. Tc-99m MDP uptake in osteopoikilosis. Clin Nucl Med. 1994;19(1):6-8.
9. Vanhoenacker FM, De Beuckeleer LH, Van Hul W, et al. Sclerosing bone dysplasias: Genetic and radioclinical features. Eur Radiol2000; 10:1423-1433.