1111
he skeletal system plays an essential role in mineral
homeostasis and mobility. The bones of the skeletal
system provide the basic framework that supports the
body, protects its organs, and provides for movement.
Joints hold the bones of the skeleton together, making
movement possible. Bone is also one of the few tissues
that normally undergo mineralization. It is a storehouse
for 99% of the body’s calcium and 85% of its phospho-
rus. This chapter focuses on two types of skeletal disor-
ders: metabolic bone diseases, which produce a decrease
in bone mass and mineralization, and joint disorders,
which disrupt mobility.
Metabolic Bone Disease
Metabolic bone disease represents disorders of bone
metabolism that result in structural effects on the skel-
eton, including decreased bone density and diminished
bone strength. The strength of bone is determined by its
composition and structure.
1
It must be rigid enough to
support the body, yet flexible enough to absorb energy
by deforming, to shorten and widen when compressed,
and to lengthen and narrow under tension without
cracking.
There are two types of bone: cortical and trabecu-
lar. Cortical or compact bone is composed of densely
packed layers of mineralized collagen; it provides rigid-
ity and is the major component of tubular bones (see
Chapter 42, Fig. 42-1). Trabecular or cancellous bone is
spongy on cross-section; it provides strength and elastic-
ity, and constitutes the major part of axial skeletal struc-
tures such as the vertebrae. Disorders in which cortical
bone is defective or reduced in mass lead to fractures of
the long bones, whereas those of cancellous bone lead
preferentially to vertebral fractures.
T
Disorders of the
Skeletal System:
Metabolic and
Rheumatic
Disorders
44
C h a p t e r
Metabolic Bone Disease
Osteopenia
Osteoporosis
Etiology and Pathogenesis
Clinical Features
Osteomalacia and Rickets
Osteomalacia
Rickets
Paget Disease
Etiology and Pathogenesis
Clinical Features
Rheumatic Disorders
Systemic Autoimmune Rheumatic Diseases
Rheumatoid Arthritis
Systemic Lupus Erythematosus
Systemic Sclerosis/Scleroderma
Seronegative Spondyloarthropathies
Ankylosing Spondylitis
Reactive Arthritis
Psoriatic Arthritis
Osteoarthritis
Etiology and Pathogenesis
Clinical Features
Crystal-Induced Arthropathies
Gout
Rheumatic Diseases in Children and the Elderly
Rheumatic Diseases in Children
Juvenile Idiopathic Arthritis
Juvenile Spondyloarthropathies
Juvenile Dermatomyositis
Rheumatic Diseases in the Elderly
Osteoarthritis
Rheumatoid Arthritis
Crystal-Induced Arthropathies
Polymyalgia Rheumatica
Management of Rheumatic Diseases in the
Elderly
