Diseases of musculoskeletal system By Dr. Abdelaty Shawky Dr. Gehan Abdel monem

Topics 1.Developmental disorders of musculoskeletal system. 2.Infectious diseases of bone and joints. 3.Metabolic bone diseases. 4.Degenerative bone diseases. 5.Neoplastic bone diseases.

1. Developmental disorders of musculoskeletal system A.Congenital hip dislocation. B.Duchenne muscular dystrophy. C.Osteogenesis imperfecta. D. Limb Anomalies – Amelia, Meromelia. – Polydactyly – Syndactyly

ILOs Identifying the definition and etiology of congenital hip dislocation. Identifying pathological features of Duchenne muscular dystrophy. Understanding etiology, Clinical manifestations of osteogenesis imperfecta. Recognizing etiology, epidemiology, pathological features and complications of paget's disease of bone.

A. Congenital hip dislocation

Normal anatomy of the hip joint

A disorder of unknown cause in which the head of the femur is displaced from its socket in the acetabulum. It is generally recognized at birth. The disorder is familial, more common in females than in males. If untreated, a false socket develops, and the individual later walks with a severe limp. * Treatment: consists of reduction of the dislocation and the use of splints to keep the femur in the socket until the joint ligaments adapt to the new position.

B. Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a form of muscular dystrophy which results in muscle degeneration and eventual death. * Etiology: * Etiology: The disorder is caused by a mutation in the dystrophin gene, located on the human X chromosome, which codes for the protein dystrophin, an important structural component within muscle tissue that provides structural stability to the dystroglycan complex (DGC) of the cell membrane. * Symptoms: Progressive proximal muscle weakness of the legs and pelvis associated with a loss of muscle mass is observed first. Eventually this weakness spreads to the arms, neck, and other areas. Due to progressive deterioration of muscle, loss of movement occurs, eventually leading to paralysis.

* Histopathology: * Histopathology: There is degeneration of muscle fibers along with some regeneration and scattered chronic inflammatory cells, fibrosis, and hypertrophy of remaining muscle fibers.

Replacement of the damaged muscle fibers by fat

* Treatment: There is no known cure for Duchenne muscular dystrophy. Treatment aims to control symptoms to maximize quality of life. Gene therapy may become available in the future. Activity is encouraged. Inactivity (such as bedrest) can worsen the muscle disease. Physical therapy may be helpful to maintain muscle strength and function. Orthopedic appliances (such as braces and wheelchairs) may improve mobility and the ability to care for yourself.

C. Osteogenesis imperfecta

Osteogenesis imperfecta (OI), also known as Brittle Bone Disease, is a heritable disorder of connective tissue. * Etiology: * Etiology: an autosomal dominant disorder of type I collagen, the major protein component in the extracellular matrix of bone. * Clinical features: Bone fragility, with a tendency to fracture from minimal trauma. Short stature, macrocephaly, blue sclera, dentinogenesis imperfecta, hearing loss and neurological and pulmonary complications. * Morphologically: * Morphologically: too little bone with marked cortical thinning and attenuation of trabeculae.

D. Limb anomalies

Absence of one or more limbs Amelia:

Meromelia Partial absence of a limb or limbs

Phocomelia Extremities resemble those of a seal. Typically, hands and feet are present (may be normal or abnormal), but the intervening arms and legs are absent

Polydactyly Poly: many, dactyl: digit (finger/toe) Presence of more than normal number of fingers or toes

Syndactyly

Absent thumb

Paget's disease of bone

Paget's disease of bone (osteitis deformans) is a localized, although sometimes multifocal, skeletal disorder of unknown cause. Is an acquired disorder of bone growth and remodelling. It usually occurs after the age of 40, increases in incidence with aging, and has slight male preponderance.

The skeletal involvement may be limited to a single bone (monostotic) or affect many bones (polyostotic), notably the pelvis, femur, tibia, spine, and skull. The affected bones may be weakened by resorption or enlarged by bone formation although defective, new-bone formation. In the final stage of the disease, dense bone is formed, but it is poorly organized and predisposed to fracture and deformity.

* Etiopathogenesis: * Etiopathogenesis: Is a disorder of bone remodeling. Increased numbers of osteoclasts initiate the remodeling abnormality with increased bone resorption at affected sites. Coupled with areas of new bone formation, with the deposition of architecturally disorganized new bone. As a consequence of this localized increase in bone turnover, there is a characteristic radiographic appearance of areas of osteolysis juxtaposed areas of new bone formation.

X.ray

There is marked frontal bossing in this patient with Paget disease. Involvement of the skull in Paget disease can lead to cranial nerve compression, nerve deafness, optic atrophy

* Histopathology: The bone changes are divisible into three phases defined radiologically: the osteolytic phase, the mixed osteolytic and osteoblastic phase, and a final osteosclerotic phase.

Osteolytic phase: In this section of bone, a multinucleated osteoclast is seen actively resorbing the surrounding bone

Osteoslcerotic phase

* Complications: 1.Pathological fracture of affected bones. 2.Hyperdynamic circulation caused by bone hypervascularity, resulting in high-output left ventricular failure; 3.Neoplastic transformation into bone sarcoma: most commonly, osteogenic sarcoma; less often, fibrosarcoma; and, rarely, giant cell tumor.

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