Final answer:
The disorder that typically affects older individuals, especially women, and causes pain and stiffness in the cervical spine and shoulder, and hip girdles with systemic infection signs is polymyalgia rheumatica (PMR). This inflammatory condition is common in aging populations and is distinct from other joint disorders like fibromyalgia or Reiter's syndrome.
Step-by-step explanation:
The disorder you're asking about is polymyalgia rheumatica (PMR). This condition particularly affects older adults and is more common in women. It is characterized by pain and stiffness in the shoulder and hip girdles along with signs of systemic inflammation such as malaise, unexplained weight loss, night sweats, and low-grade fever. These symptoms are not typically observed in patients with fibromyalgia syndrome, myofascial somatic syndrome, or Reiter's syndrome, making PMR the most likely diagnosis given the symptoms you've described.
As individuals age, the risk of developing joint disorders like polymyalgia rheumatica increases. PMR can be associated with another condition called giant cell arteritis, which must be treated promptly to prevent complications such as blindness. Though the cause of PMR is not entirely understood, it is considered an inflammatory disorder and is often treated with corticosteroids to reduce inflammation and pain.