Melorheostosis: a rare entity: a case report

Melorheostosis is a rare entity belonging to the group of sclerotic bone dysplasias. Described for the first time in 1922 by Leri, it remains imperfectly known as clinical presentations are highly variable, and the etiological diagnosis is not fully elucidated. We report a case of polyostoticmelorheostosis for which radiological investigations were complete, in order to study this disease.


Introduction
Melorheostosis is a rare benign non hereditary condition. It is known as a mesoderm sclerotic bone dysplasia, characterized by cortical hyperostosis with or without retraction of soft tissue. It was described for the first time in 1922 by Leri and Joanny as a dripping candle wax hyperostosis [1]. Since then, 300 cases have been reported in the literature. Its incidence is estimated 0.9 per million population [2]. It affects both men and women at any age. The locations are highly variable, and mono ostotic forms were more often described. Polyostotic forms localized to the lower limbs are rare. The disease can remain silent and be discovered incidentally.
If not, symptoms are made of distortion, variable pain or limitation of joint mobility. It is a disease whose etiology is imperfectly understood, the genetic factors and metabolic predisposition or malformation of the vessels are proposed, but the exact cause is to be determined [3][4][5]. The diagnosis was facilitated by the recent imaging techniques, CT scan or better, the MRI that provides diagnostic certainty [6,7]. Scintigraphy can detect subclinical lesions and monitor its progress [6,7]. Therapeutic envisaged vary widely, depending on the discomfort and the localization.

Patient and observation
We report the case of a 39 years-old female, with no past medical history, whose complaint was a spontaneous one week evolving isolated left cruralgia. The clinical examination was unremarkable apart from an anterior thigh pain at the mobilization of the left hip.  (Figure 4). Given these findings, biopsy was not performed, and the patient was discharged to be followed in our consultation by standard radiographs every three months, and an annual bone scan.
At last follow up, two years of the first consultation, two episodes of left cruralgia have been reported, and yielded by three days antiinflammatory treatments. Scintigraphy ( Figure 5) and plain radiographies remained similar to initial assessments.

Discussion
Melorheostosis is still an imperfectly known pathology and many questions remain unanswered. The role of a genetic predisposition has been suggested, but evidence does not yet exist considering that familial cases have not yet been reported. Its association with vascular sector malformations and some observations reported changes in skin pigmentation suggests that a mutation may be responsible [3][4][5].
In this rare disease, the clinical presentations are highly variable and locations are diverse. Both upper or lower limbs can be affected in addition to the axial skeleton. The lower limbs are affected more often than the upper limbs. Conventional imaging is very characteristic when it shows the flowing candle wax, but this aspect can be seen in other conditions such as osteomyelitis or bone tumor. In some presentations it may be lawful to biopsy and perform bacteriological examinations [7]. In the most common cases, imaging may be sufficient to make the diagnosis. Crosssectional imaging is very essential: CT shows bone lesions with its classical aspects and quantifies it in the spatial planes [6,7] whereas MRI can describe the extension to the soft tissues and rule out possible differential diagnoses [6,7]. Bone scintigraphy has an important contribution in melorheostosis since it can detect subclinical lesions and monitor progress. It also allows to differentiate the developmental stages according to the intensity of the bone fixation [6,7]. We recommend monitoring by full body scans to detect any changes, especially since the evolution is unpredictable.
The therapeutic is not well codified. It is symptomatic in most cases, in order to control bone pain. Protocols based on Pamidronate [8] have been proposed and appear to improve symptoms but do not slow the progress. Surgery is indicated in cases where there is major axial deformation or consequent limitations of joint mobility.
Page number not for citation purposes 3 It is not easy and a knowledge of soft tissues involvement is a prerequisite.

Conclusion
Melorheostosis is a rare, benign with chronic course, often with outbreaks interspersed with remissions. We emphasize the need to ensure the diagnosis by plane radiographies, CT scan or MRI. If any doubt, biopsy may be necessary. Scintigraphy is the best exploration for monitoring the disease. Treatment is symptomatic essentially, based on nonsteroidal anti-inflammatory. Surgery can have its place in large deformations and joint damage, but with great care.

Competing interests
The authors declare no competing interest.

Authors' contributions
All the authors have contributed to this manuscript in ways that comply to ICMJE authorship criteria. All the authors have read and approved the final version of themanuscript.