Radiology Rounds
Round # 15
Correct Diagnosis: Type II Autosomal Dominant Osteopetrosis (Albers- Schnberg Disease)
Discussion:
Type II Autosomal Dominant Osteopetrosis (Type II ADO), also known as Albers- Schnberg Disease, is a rare bone dysplasia characterized by diffuse and symmetric bony sclerosis most often affecting the long bones, skull, ribs, and spine. A rarer autosomal recessive form affects children, and is often fatal by the end of the first decade of life. Patients with Type II ADO often present by the early 20s with a history of recurrent long bone fractures, deep dental caries complicated by abscesses, mandibular osteomyelitis, or cranial nerve palsies secondary to basilar skull sclerosis. Early degenerative joint disease, especially in the hips is also seen. Despite their diffusely thickened bone, these patients are prone to fracture, likely due to the thickened bonesdecreased torsional strength. However, this same property likely protects patients from vertebral fractures, which are quite rare in this condition. The condition is easily diagnosed radiographically with its characteristic sandwich vertebrae seen on spine films. A similar appearance may also be seen in patients with renal osteodystrophy (the rugger jersey vertebrae), but the clinical setting helps distinguish between the two entities.
Orthopedic surgery is notoriously difficult in these patients; drill bits often break, intraoperative fractures occur due to the surprisingly brittle and inelastic bone, and postoperative infections and abscesses are common due to decreased bone vascularity. The disease is thought to be due to defective osteoclast function, although an exact etiology remains unknown. An increased serum acid phosphatase is generally seen in these patients and they may be mildly anemic due to a decreased marrow space. Treatment is largely symptomatic and often involves meticulous fracture management and close postoperative care.
References:
- Stoker DJ. Osteopetrosis. Semin Musculoskelet Radiol 6(4):299-305, 2002.
- Armstrong DG, Newfield JT, Gillespie R. Orthopedic management of osteopetrosis: results of a survey and review of the literature. J Pediatr Orthop 19(1):122-32, 1999.
- Vanhoenacker FM, De Beuckeleer LH, Van Hul W, Balemans W, Tan GJ, Hill SC, De Schepper AM. Sclerosing bone dysplasias: genetic and radioclinical features. Eur Radiol 10(9):1423-33, 2000.
- Benichou OD, Laredo JD, de Vernejoul MC. Type II autosomal dominant osteopetrosis (Albers-Schonberg disease): clinical and radiological manifestations in 42 patients. Bone 26(1):87-93,2000.
