Description, Causes and Risk Factors:
Melorheostosis is a rare and progressive disorder characterized by hyperostosis (thickening) of the cortical bone. Melorheostosis affects both bone and soft tissue growth and development. Melorheostosis can result in severe functional limitation, extensive pain, soft tissue contractures, and limb, hand an/or foot deformity.
Melorheostosis was first described in 1922 by Leri and Joanny as "hyperostose en coulee" that is following hyperostosis resembling dripping candle wax.
The etiology of melorheostosis is unknown. Both melorheostosis, osteopoikilosis, and Buschke-Ollendorff syndrome have recently been described due to a loss-of-function mutation in LEMD3 gene. LEMD3 gene encodes for an integral protein of the inner nuclear membrane. The developmental error is at the site of both intramembranous and endochondral bone formation, predominantly the former. Its distribution often suggests a sclerotomal abnormality involving one or more sclerotomes or areas of bone innervated by an individual spinal sensory nerve. There is a definite tendency for monomelic distribution that is involvement of one limb, but a single bone or multiple different bones may be affected. Melorheostosis also shows a linear track involvement along the diaphysis/metaphysis/epiphysis, at times crossing contiguous bones and joints.
Melorheostosis is somewhat more common in individuals who have osteopoikilosis, an unusual benign disorder characterised by a spotty appearance to the ends of the bones. This is associated with mutations in the LEMD3 gene but does not usually have clinical consequences. Melorheostosis itself affects the tissues in a segmental fashion and does not follow a Mendelian pattern of inheritance. Most cases occur sporadically in the general population (but somewhat more commonly against the background of osteopoikilosis in the family) and the genetic/biochemical cause is not known for certain.
Age and presentation varies widely and melorheostosis may be seen in children and adults. There is no sex predilection. Other diseases associated with melorheostosis include, osteopoikilosis, osteopathia striata, scleroderma and Buschke-Ollendorff syndrome.
The course of the disease is insidious, with a slow chronic progression of symptoms and periodic exacerbation. Soft tissue involvement is associated with more evident restricted motion and stiffness due to soft tissue contracture, fibrosis an even ossification. There may be an associated limb length discrepancy, tendon and ligament shortening, or rarely a malformation of blood or lymph vessels, and/or soft tissue fibromatosis. Limb swelling and edema may be seen as well as hyperpigmented skin patches or linear sclerodermatous skin changes.Signs: Serum calcium, phosphorus, and alkaline phosphatase are normal.
Other symptoms may include:
Limb length inequalities.
Joint swelling and fusion.
Soft tissue abnormalities including tendon and ligament shortening, absent or abnormal muscles, calcification contractures resulting in malformed or immobilized joints.
Range of motion limitations.
Pain and stiffness.
Sensitivity to cold
Hyperpigmentation of skin.
Irregular bone growth including cortical thickening and `candle wax' appearance.
The age of diagnosis is typically based on the severity of onset and symptoms.
Imaging: On x-rays, the appearance of melorheostosis been likened to flowing, melted candle wax. Cortical hyperostosis is readily seen on plain radiographs, extending along the lenght of one side of the bone and resembling flowing candle wax. In the carpal and tarsal bones and in the epiphyse, the hyperostosis may be round or irregular. Soft tissue calcification or ossification may be seen.
Scintigraphy reveals abnormal increased tracer uptake in the bone and soft tissue lesions. It may be instrumental in confirming the diagnosis in equivocal cases. Computed tomography will also reveal the lesions and the clear demarcation between normal and abnormal bone. Magnetic resonance lesions as areas of low signal on all sequences. CT and MRI are not needed for diagnosis in the vast majority of cases especially in children.
The disease is of variable severity, but in general follows a chronic progressive course in adults and more faster course in children, occasionally resulting in substantial disability from contractures or deformity. Conservative management is often unrewarding, and in severe cases surgical intervention may be required, including tendon release, osteotomies and even amputation. In extremely rare cases, amputation is indicated in very painful limbs with contractures and ischemia. Most cases are benign and do not require operative intervention.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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