Melorheostosis: a rare case

A 12-year-old male presented with complaint of difficulty in walking since 6years with limitation of movement at right hip joint. On physical examination, there was shortening of right lower limb by 6 cm. Muscle wasting was present in thigh.

X-ray bilateral hip joint (Figure 1): Mild tilting of the pelvis on the right side with mild reduction of the right hip joint space with an area of sclerosis in head and neck of the femur on the right side with extensive, dense, undulating endosteal thickening, resembling candle wax, extending along the length of bone, resulting in narrowing of the medullary cavities.

X-ray bilateral foot (Figure 2): Irregular endosteal thickening noted in tarsals, metatarsals and phalanges of the right foot.

MRI right hip joint with thigh: Mild tilting of the pelvis on the right side with mild reduction of the right hip joint space with area of sclerosis in head and neck of the femur on the right side (Figure 3a and 3b) with endosteal thickening of shaft of femur with narrowing of medullary cavity with associated disuse atrophy of gluteal and thigh muscle on the right side (Figure 3c).

Melorheostosis (synonyms: candle bone disease, melting wax syndrome, Leri disease), first described by Leri and Joanny in 1922 [1]. It is a rare benign disorder characterized by mesodermal dysplasia of bone. It is derived from the Greek word melos = limb and rheos = flow due to the classic radiological appearance of ‘flowing hyperostosis’ resembling hardened wax that has dripped down the side of a candle. Men and women are equally affected, and no hereditary features have been discovered. The disorder begins in childhood. The most common symptom is pain and the onset of the disease is insidious [2]. It mainly affects, the long bones of the upper and lower limbs, and also the short bones of the hand and foot, but rarely the axial skeleton [3,4].  The most common part of the bone is diaphysis of the long bone of the lower limb rarely the axial skeleton. It may also present with limb-length discrepancy, joint stiffness, progressive deformity, ossification in adjacent soft tissues [3]. The exact cause of disease still remains unclear. Skin changes may be seen in about 17% of cases and that may include hyperpigmentation of overlying skin and scleroderma. Melorheostosis may present in a monostotic, polyostotic, or monomelic form. The monomelic variant is the most common presentation of this rare disease [5].

Routine laboratory findings usually are normal. Histologic findings are usually nonspecific and often show dense bone formation, a mixture of mature and immature bone elements[6]. Osteoclastic activity is not a prominent feature; however, osteoblastic activity along the margins of osteons is common[7]. Treatment is mainly symptomatic. Most patients receive nonoperative treatment. Operative treatment consists of tendon lengthening, excision of hyperostotic bone, osteotomies, sympathectomy and amputation[4]. Bisphosphonate are commonly used.

Conclusion

Radiographs of hip joint, femur and foot, MRI of the hip joint and histopathology report were consistent with Monomelic Melorheostosis involving right hip joint, right femur and tarsals, metatarsals and phalanges of the right foot which played key role in diagnosis and management. Melorheostosis can only be diagnosed by characteristic candle wax type appearance in x-ray film. Patient was advised symptomatic treatment in the form of Pamidronate and physiotherapy which leads to relief of pain and an increase in range of movement.

Clinical Message

It is a very rare benign disease. It is diagnosed by characteristic x-ray findings. There is no definite treatment available only symptomatic treatment and deformity correction can be done.