Discussion
We report here a case of IMOS in a 53-year-old man. To the best of our knowledge, there are less than twenty cases reported in literature.
In the series of Kullanuch Chanchairujira and al, nine female patients with leg pain and imaging signs of IMOS were detected during a 25-years period [3]. Kensaku Abe and al reported three cases (one man, two women) of osteosclerotic lesions (femoral diaphyses, tibial diaphysis) examined between 2015 and 2019 [2]. Vasilios Skiadas and al presented the case of a 60-year-old woman with a bilateral midfemoral pain for 8 years[4]. In the case of Balkissoon and al, a 39-year-old woman experienced intermittent severe pain in both lower legs for several years[5].
These data suggest that this condition is more common in women than in men unlike our case.
No similar musculoskeletal illness was found in any patient’s family history. None of these patients have a history of trauma or infection. No abnormal laboratory results including inflammatory reaction were observed [2,3,4], such in our case.
The diagnosis of intramedullary osteosclerosis was retained after the exclusion of disorders related to osteosclerosis, including osteosarcoma, lymphoma, metastasis, stress fractures, metabolic disorders and other sclerosing bone dysplasia [1,5]. Metabolic disorders such as renal osteodystrophy, hypervitaminosis A and pseudohypoparathyroidism need to be considered. Generalized osteosclerosis is more characteristic of renal osteodystrophy and pseudohypoparathyroidism. Hypervitaminosis A may lead to a periosteal bone formation. Normal laboratory findings and clinical features can eliminate these causes [3,9]. Only two known conditions, Camurati-Engelmann disease and Ribbing disease are presented with radiological and scintigraphic peculiarities similar to those of osteosclerosis intramedullary. But, they can easily be dismissed since the two are hereditary: (Engelmann: autosomal dominant, Ribbing: autosomal recessive)[10,11].
Radiographs revealed, in the case of Vasilios and al, diffuse bilateral asymmetric diaphyseal sclerosis of femoral bones, predominantly endosteal, more extensive on the left side, with mild expansion and cortical thickening of the affected segments. No periosteal reaction was seen [4]. In the case of Balkissoon and al, The radiographs demonstrated bilateral asymmetric mid-tibial and minimal fibular shaft endosteal cortical scleroses. There was no substantial soft-tissue abnormality [5]. In the cohort of Kullanuch Chanchairujira and al, 16 bone lesions were identified. All were located in lower extremities. Both lower extremities were involved in the majority of patients. A single extremity was involved in two patients. Cortical thickening was seen in 10 bones and soft-tissue swelling was seen in eight lesions. No periosteal reaction was seen [3]. Radiographs of the legs showed bilateral hyperostosis involving the mid-third of the tibias in the case of Rosenberg and al[6] and diffuse diaphyseal sclerosis of the femur with widening of bone and endosteal hyperostosis in the case of Puranik and al[7] .The clinical and radiographic findings in our patient supported those studies.
Computed tomography (CT) scans showed, in these series intramedullary sclerosis and soft-tissue swelling adjacent to the cortex. The cortex was intact but thickened [2,3,4,8]. In the case of Balkissoon and al, CT scan proofs were not available such as in our case [5].
Concerning MRI findings, MR images showed a low signal intensity on images obtained with all pulse sequences, minimal increased signal intensity was seen on T2-weighted images. Gadolinium-enhanced T1-weighted fat-saturated images were obtained, and the images revealed minimal enhancement in the lesions or surrounding soft tissue [2,3,4]. In our case, MRI findings were not available.
Skeletal scintigraphy was performed in five patients with nine lesions in the series of Chanchairujira and al. It showed intense tracer uptake corresponding to the abnormalities seen on conventional radiographs [3,4,6]. In one patient with bilateral lesions, an asymptomatic lesion was incidentally found in an area that appeared normal at conventional radiography [3].  Abe K and al and Puranik and al found that whole body 99mTc-methylene diphosphonate (MDP) bone scan showed abnormal tracer uptake with intense sclerosis in the intramedullary region. Moreover, triphasic bone scan was performed : the initial vascular phase and blood pool images at 2 min (phase 2) showed no evidence of increased vascularity or soft tissue tracer pooling. Delayed bone images (phase 3) showed a fusiform-shaped intense area of tracer uptake in the diaphysis [2,7]. In our setting, scintigraphy was not performed.
Open biopsy was carried out and histologic findings were available in the series of Chanchairujira and al, but were non specific. The peripheral and major part of the lesion was characterized by the replacement of normal spongiosa by markedly sclerotic trabeculae and were seen radiographically as osteosclerosis. There were some areas of osteoblastic rimming of the trabeculae. Centrally, cell proliferation associated with immature collagen deposition was noted [3]. In the cases of Abe K and al, the histology showed trabecular bone sclerosis with hypocellular fibrous tissue. The culture was negative[2]. Culture was sterile in the case of Vasilios and al. Pathologic examination revealed a replacement of normal spongiosa by markedly sclerotic and thickened trabeculae, obviously, seen radiographically as osteosclerosis, in the case of Puranik too [4,7].
The management of intramedullary osteosclerosis is not well described in the literature and is not yet standardized.
NSAID seem to be effective in this disease. Indeed, in our case, the patient improved after prescription of diclofenac and he was relieved in the followup. In the case of Skiadas and al, the patient also showed improvement following NSAID therapy administered for one month [4]. In the series of Abe and al, pain was uncontrolled
by even opioid use[2]. In our case, the association of NSAID and level 2 analgesic was sufficient.
Open surgical biopsy seems to be also an efficient treatment of IMOS. In fact, besides the diagnosis confirmation, this technique allowed medullary decompression. In the Kensaku and al series, open biopsy was able to reduce the intensity pain, which is controlled afterwards only by NSAID [2].
Although ,there were limitations to our study, such as the lack of CT, MRI, scintigraphy and histologic results, we believe that our study and our review of the literature can add data to this still unknown disease.