Ribbing disease – A Rare cause for Common Shin Pain

Ribbing Disease, also known as Hereditary Multiple Diaphyseal Sclerosis, manifests itself around the 3^rd-4^th decade of life through extremity pain, predominantly of the shins. Its etiology is considered as an uncontrolled diaphysary growth of the endosteum and periosteum of the long bones, guided by tilting the coupled bone formation and resorption towards bone formation[1]. Ribbing disease does not seem to be weakening the structural integrity of the bone. Nonetheless, there is a slow progressive obliteration of the cancellous bone and the Haversian system, and its replacement by a dense cortical bone[3]. Genomic studies have suggested the involvement of the TGFβ1 gene, which takes part of the TGF-BMP pathway, responsible for the osteoblast differentiation and osteogenesis. This rare disease is transmitted through an Autosomal Recessive pattern, with reports surmounting up to only few world wide. There are many etiologies that can lead to the presentation of cortical thickening, with differential diagnosis being Infection (chronic osteomyelitis), Endocrinology abnormalities, Stress Fracture, Paget's Disease and Neoplasias (mainly Osteoid Osteoma and Osteosarcoma)[2].  Diagnosis of Ribbing Disease is done by means of clinical interview, physical examination and radiology. To date there is only a nosologic classification system for bone dysplasiae[3], where Ribbing Disease partake the group of "other bone dysplasiae" (Table 1). X-rays facilitates the diagnosis, delineating the fusiform thickening of the cortices at the expense of the medullary cavity. Computer Tomography is not mandatory, however it assists with the biopsy of the affected bone (figure 2). Bone Scan are useful for the detection of different foci of the disease at the systemic level. The serum levels of calcium, vitamin D3 and the Parathyroid hormone can help identifying endocrinology abnormalities, whereas Alkaline Phosphate and Lactate Hyrdrogenase indicate the intensity of activity of the Osteoblasts and Osteoclasts, respectively. Herein, MRI can be used primarily in order to rule out an alternative etiology, especially neoplasia. In the case of Ribbing disease, it will demarcate in the T2 phase the bone edema[4], resembling an intramedullary high pressure, which is thought to be the cause of pain. Conservative measures is the first line of treatment of Ribbing Disease, and it includes the use of anti-inflammatories such as NSAIDs[5] and steroids to lower the edematous pain. Bone anti-resorption medications, especially bisphosphonates, may be used in order to alternate the coupled bone remodeling process. It use is controversial, as it targets the osteoclasts instead of the osteoblasts, which are the protagonists of this disease. The success rate of these medications is undetermined, with conflicting results[5-8], and attempts to correlate genomics with a good-to-excellent response to treatment did not succeed[9]. Our attempt to apply Salmon Calcitonin, yet another Osteoclast inhibitor, seeing an anecdotal success with another bone dysplasia[10], did not work. There has been no use of anti-TGFβ antibodies to counter the disease to date. The use of TGFβ pathyway inhibitors, such as Angiotensin Converting Enzyme Inhibitors (ACEi) and Angiotensin Receptor Blockers (ARBs) has not been described in the literature for Ribbing Disease, however there are reports about good outcomes in a similar TFGβ-driven disease, Englemann-Camurati disease[11]. We have tried Losartan with our patient, to no avail. It is possible that its effectiveness in Englemann-Camurati is derived from its elevated osteogenic activity, in respect to the latency of Ribbing Disease. The second line of treatment is surgical intervention which will reduce the intramedullary pressure. Intramedullary reaming, without the use of instrumentation or Polymethylmethacrylate (PMMA), as the bone is already stable. The reaming is believed to decompresses the intramedullary cavity, thereby dramatically decreasing the pain level, albeit not necessarily abutting it[12]. With the obliteration of the medullary cavity by the endosteal bone, breaching the canal is not expected to be smooth, and may require the use of hammers and manual reamers. Intraoperative fluoroscopy must be performed to rule out an unintended cortical breach and fracture. Cortical fenestration is also reported however it may not be as effective as reaming due to its limited decompression.