Melorheostosis

A 23-year-old female presented with painful, slow-growing masses on the left thumb and forearm for 5 years. The medical history revealed no trauma and no sports-related injury. The musculoskeletal examination revealed painful supination of the forearm and thumb movements. There was full range of all other joints of the fingers and wrist, with absent contractures or rotational deformity. A hard mass approximately 1 cm by 1.5 cm was identified extending over the phalange of the right thumb and radial side of the forearm 1 cm in size. This region was firm and painful to palpation. Superficially, there was no evidence of discoloration, skin thickening, or local increase in warmth. 

Sensibility in the fingers was intact with no muscular atrophy. Laboratory tests, including complete blood count, serum phosphorus, alkaline phosphatase, calcium level, erythrocyte sedimentation rate, and C-reactive protein, were normal.

Conventional roentgenographs of the left hand and forearm (Figures 1a and 1b) showed cortical hyperostosis and thickening with “dripping wax” appearance of the first and second metacarpals, proximal and distal phalanx of the thumb, proximal and middle phalanx of the second digit, carpal bones, radius and distal humerus, with no soft tissue ossification.

MRI was performed for further evaluation of osseous and possible tissue abnormalities (Figures 2a and 2b). The classical cortical hyperostosis characteristic of melorheostosis was seen with no reactive soft tissue inflammation, tissue masses, or tumors were demonstrated. Based on the roentgenographic and MRI findings, the patient was diagnosed with melorheostosis—a rare benign sclerosis of bones and soft tissue.

Discussion. Melorheostosis is a rare osteosclerotic bone dysplasia. It is a nongenetic developmental anomaly first described in 1922 by Léri and Joanny.^1,2 The etiology and pathogenesis is unknown. The age of presentation is varied, ranging from neonates to elderly, however most commonly presenting between 5 and 20 years of age with no sex or ethnic predilection.³ Melorheostosis usually affects the upper limb (22%), lower limb (70%), upper and lower extremities (4%), and axial skeleton (4%).^{3
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Classic radiograph findings are of cortical hyperostosis along the length of the bone with a dripping candlewax appearance. There is usually a clear distinction between the normal and affected bone. Sclerotic linear areas are seen mainly in the cortex but also extending into the trabecular bone. The pattern of bony changes are variable and there have been 5 patterns identified radiographically, which include osteoma-like pattern, classic candle wax appearance, myositis ossificans-like pattern, osteopathia striata-like, and mixed pattern. 

Onset is usually gradual—pain, deformity of the extremity, stiffness, and limited motion in joints first presenting in early adolescence and progressing into adult life. Patients can have associated cutaneous and soft tissue lesions, such as vascular malformation, neurofibromatosis, linear scleroderma, tuberous sclerosis, hemangiomas, and focal subcutaneous fibrosis and arterial aneurysms.⁴ The diagnosis of melorheostosis is usually made by the classical plain radiographic findings. CT and MRI can further characterize the lesion, but rarely contribute to the diagnosis. Histology is nonspecific. 

Differential diagnosis. The differential diagnosis includes disorders with periosteal and/or endosteal thickening (eg, osteoma, periosteal osteosarcoma, and myositis ossificans when soft tissue ossification is present). Other conditions, including osteomyelitis, osteopetrosis, osteopoikilosis, pycnodysostosis, and osteopathia striata, can have similar radiographic findings.^5,6

Treatment. There is no specific treatment for melorheostosis. Chronic conditions are managed nonoperatively with conservative measures, such as pain control with NSAIDs and physical therapy. Preservation of motion is an important aim, but more invasive measures may be necessary when nonoperative measures fail. Intensity of pain is thought to be associated with extension of hyperostosis and into the bone marrow secondary to compromised blood circulation due to increased intraosseous pressure.

The pain can be caused by carpal tunnel syndrome, and surgical intervention relieved the symptoms in majority of the patients. In patients with intraosseous, osteoma-like lesion, surgical debulking of the hyperostotic cortex and cortical fenestration have been successful.^7-13

Outcome of the case. This patient declined surgical correction and chose to do conservative pain control with NSAIDs and physical therapy with close clinical monitoring.

References:

1.  Greenspan A, Azouz EM. Bone dysplasia  series. Melerheostosis: review and update. Can Assoc Radiol J. 1999;50(5):324-330.

2.  Leri A, Joanny J. Une affectione non décrite des os Hyperostose ‘en couléé’ sur toute la longeur d’un membre our ‘mélorheostose.’ Bull Mém Soc Med Hôp Paris. 1922;46:1141.

3.  Freyschmidt J. Melorheostosis: A review of 23 cases. Eur Radiol. 2001;11(3):474-479.

4.  Birtane M, Eryavuz M, Unualan H, Tuzun F. Melorheostosis: Report of a new case with linear scleroderma. Clin Rheumatol. 1998;17(6):543-545. 

5.  Fernandes CH, Matheus RP, Faloppa F, Albertoni WM. Alterações esqueléticas da mão na picnodisostose. Rev Bras Ortop. 1996;31:441-442.

6.  Judkiewicz AM, Murphey MD, Resnik CS, et al. Advanced imaging of melorheostosis with emphasis on MRI. Skeletal Radiol. 2001;30(8):447-453. 

7.  Barfred T, Ipsen T. Congenital carpal tunnel syndrome. J Hand Surg. 1985;10(2):246-248.

8.  Campell CS. Melorheososis of the upper limb. Report of a case. J Bone Joint Surg. 1955;37-B(3):471-473. 

9.  Caudle RJ, Stern PJ. Melorheostosis of the hand. A case report with long-term follow-up. J Bone Joint Surg. 1987;69(8):1229-1231.

10. Murray RO, McCredie J. Melorheostosis and the sclerotomes. A radiological correlation. Skel Radiol. 1979;4(2):57-71. 

11. Rozencwaig R, Wilson MR, McFarland GB. Melorheostosis of the skeletally immature hand: a case report and long term follow-up evaluation. J Hand Surg. 1996;21(4):703-706. 

12. Sharma R, Burke FD. Melorheostosis of the hand. J Hand Surg. 1996;21(3):413-415. 

13. Waiter JM, King JC, Louis DS, Smith J. Melorheostosis of the hand: a comprehensive review. Hand Surg. 1998;3:123.