Final answer:
Among the options provided, Osteopenia is the condition that presents as reduced bone mass. It is a precursor to osteoporosis, which is defined by decreased bone density and an increased risk of fractures.
Step-by-step explanation:
The condition that presents as reduced bone mass among the options provided is Osteopenia. Osteopenia is a precursor to osteoporosis, which is characterized by a progressive reduction in bone density, leading to skeletal weakness and an increased risk of fractures. Osteoporosis involves both excess bone resorption and insufficient production of new bone tissue, primarily involving the bone cells known as osteoclasts (which resorb bone) and osteoblasts (which form new bone). Risk factors for osteoporosis include older age, XX chromosome, European or Asian ancestry, family history of osteoporosis, short stature, small bones, lack of estrogen, and inadequate levels of calcium and vitamin D, which can lead to impaired bone formation by osteoblasts during remodeling.
In contrast, osteomyelitis is an infection in the bone, osteoarthritis is a degenerative joint disease that does not primarily involve reduced bone mass, and osteomalacia refers to softening of the bones usually due to a deficiency in vitamin D or phosphate.