1. ID 1184 RIBBING DISEASE

2. INTRODUCTION: Ribbing disease is a rare form of sclerosing bone dysplasia characterised by formation of exuberant but benign endosteal and periosteal new bone. It was an uncommon cause of leg pain in post pubertal young females. It is either unilateral or asymmetrical and asynchronously bilateral.

3. It affects only long bones especially diaphysis of tibia and femur. Most patients present with pain. It is often confused with sclerosing osteomyelitis, stress fracture, bone forming tumours or other sclerosing dysplasia.

4. CASE REPORT: 35Yrs old thin built female presented with complaints of right leg pain for 1 ½ yrs. There was no history of trauma or fever. No history of autoimmune disease in her family. On examination, There was no clinical signs of infection, no evidence of bony tenderness. Hematological parameters and markers of bone metabolism were normal.

5. She underwent radiograph of leg which showed cortical thickening of diaphysis of right tibia involving both endosteal and periosteal cortex and medullary sclerosis. Contralateral tibia and bilateral femora were normal. She further underwent MRI which showed T1,T2 hypointense lesion with bone marrow edema in right tibial diaphysis. Screening CT was done to rule out bone forming neoplasms. There was no nidus, cortical breach or fracture line seen in this patient.

6. Anteroposterior and lateral radiographs of right leg shows cortical thickening of right tibial diaphysis involving both periosteal and endosteal cortex and reduction of medullary cavity. Left tibia, bilateral femora were normal.

7. MRI –T1 CORONAL MRI- T1 Coronal image shows cortical thickening of right tibial diaphysis with hypointense signal in mid diaphysis. Left tibia is normal.

8. MRI -T2 FAT SAT CORONAL MRI -T2 FAT SAT Coronal image shows hypointense diaphyseal lesion with surrounding oedema.

9. MRI-T2 AXIAL MRI T2 Axial images show cortical thickening with near complete occlusion of medullary cavity and bone marrow edema.

10. CT SCREENING Coronal CT of leg shows geographic diaphyseal sclerotic areas with thickened cortex and medullary sclerosis. Left tibia is normal.

11. CT SCREENING CT images of right leg show diaphyseal cortical thickening (homogenous increased density)involving both endosteal and periosteal cortex with near complete obliteration of medullary cavity. Left tibia is normal.

12. DISCUSSION: In 1947,RIBBING described a family with 4 out of 6 siblings with diaphyseal sclerosis of long bones. He designated the term heriditary multiple diaphyseal sclerosis. It is an autosomal recessive disease with uncommon cause of leg pain. Ribbing disease presents with leg pain and studies demonstrated that marrow edema is associated and responsible for pain.

13. In ribbing disease markers of bone formation and resorption are normal. But Tc 99m-MDP scan shows intense irregular uptake in diaphyseal region of tibia in delayed and blood pooling phases. The lack of elevation of bone turnover markers is explained by limited amount of skeleton involved. Area of affected bone is too small to affect overall bone turnover markers.

14. There are many sclerotic bone disorders that can be confused with Ribbing Disease. In the patient who presents with unilateral increased density and thickness of the tibia, differential diagnosis includes stress fracture, intramedullary ostesclerosis, chronic sclerosing osteomyelitis, osteoid osteoma and bone forming tumours. Chronic sclerosing osteomyelitis mainly affects metaphyseal region of long bones causing bony sclerosis and expansion.

15. Stress fractures have history of overuse and complaints of pain and swelling over the affected region. It mainly affects bones of lower leg and foot and it have visible fracture line. Osteoid osteoma have radiolucent nidus. Bone forming tumours have bone expansion, soft tissue components and periosteal reaction.

16. Bilateral increased density and thickness of the tibia may be associated with bone dysplasias such as Camurati- Engelmann disease, Erdhiem Chester disease, intramedullary osteosclerosis. Engelmann-camurati disease is an autosomal dominant disorder presents during childhood causing bilateral and symmetrical involvement of diaphysis of long bones and also affects skull. Chester disease has bilateral, symmetrical involvement and widespread systemic features. Intramedullary osteosclerosis has similar imaging features as ribbing disease but not associated with marrow edema.

17. The treatment of ribbing disease is mainly symptomatic and done with Non Steroidal Anti- Inflammatory Drugs. Bisphosphonates have limited role. Medullary rimming is a surgical treatment when medical management fails.

18. CONCLUSION : Ribbing disease is a rare diaphyseal sclerosing dysplasia. With lack of clinical signs of infection and biochemical evidence of metabolic bone disease, positive clinical and imaging features helped us to arrive a correct diagnosis.

19. References : Resnick-Diagnosis of bone and joint disorders 3 rd edition: Volume 6,Section XV111 Chapter 93 : 4416- 4420. Nishikant AD et al., Ribbing disease: uncommon cause of a common symptom. Indian J Nucl Med. Jan-Mar 2011; 26(1):36-39. Ozturkmen Y et al., Ribbing disease: a case report and literature review. Acta Orthop Traumatol Ture. 2011; 45(1): 58-65. Seeger LL et al., Ribbing disease(a diaphyseal sclerosis): Imaging and differential diagnosis. AJR: september 1996; 167. Gaeta M et al., MRI in Ribbing disease- a case report. ACTA orthopaedica 2009; 80(5):893-99. Greenspan A et al.,orthopaedic imaging-A practical approach.5 th edition,page 958, 2011.