A 65-year-old woman presents to the GP complaining of fatigue and weakness over the last four months. She says she feels stiff, especially around her shoulders and hips. On examination, all movements are 5/5 power using the Medical Research Council (MRC) muscle scale. She does not report any headaches and has no skin rashes.

What is the most likely diagnosis?

Options:
explanation: Polymyositis is a type of idiopathic inflammatory myopathy caused by autoimmune damage to the muscle. This typically presents as bilateral, proximal muscle weakness. Polymyositis is a key differential for polymyalgia rheumatica, however as this patient has normal muscle power on examination, a diagnosis of polymyalgia rheumatica is more likely
name: Polymyositis
label: c
answer: no
explanation: Polymyositis is a type of idiopathic inflammatory myopathy caused by autoimmune damage to the muscle. This typically presents with bilateral, proximal muscle weakness with associated skin rashes (including heliotrope rash, Gouttron's papules and mechanic's hands). Dermatomyositis is a key differential for polymyalgia rheumatica, however as this patient has normal muscle power on examination, which makes a diagnosis of polymyalgia rheumatica more likely. They also do not have any skin disease, making a diagnosis of dermatomyositis less likely
name: Dermatomyositis
label: d
answer: no
explanation: Polymyalgia rheumatica is an inflammatory condition that causes inflammatory pain, stiffness and systemic symptoms, typically affecting those >50 years old. The pain and stiffness typically last more than 30 minutes, is relieved by exercise, and affects the shoulder and hip girdles. These patients often report muscle weakness and other systemic symptoms, including weight loss, fever, malaise and fatigue. Typical examination findings include normal power (as in this case), which differentiates it from other key differentials such as myositis. This patent should have blood tests done, including ESR and CRP. Treatment of polymyalgia rheumatica is commended after diagnosis, typically with oral steroids (e.g. prednisolone). This is in contrast to a patient presenting with features of giant cell arteritis, who would be started on steroids before the diagnosis is confirmed
name: Polymyalgia rheumatica
label: a
answer: yes
explanation: Giant cell arteritis is an inflammatory large vessel vasculitis affecting the temporal arteries. Typical symptoms include temporal headache, jaw claudication (pain upon repeated movement of the jaw, e.g. chewing), scalp tenderness (e.g. while brushing hair) and ocular complications (e.g. blindness, amaurosis fugax). This typically affects patients >50 years old and can be associated with polymyalgia rheumatica. As this patient has not had any of these symptoms, it is more likely this is simply a diagnosis of polymyalgia rheumatica. It is important to safety net this patient for these symptoms, as they should be started on prednisolone at presentation of suspected giant cell arteritis, instead of once the diagnosis has been confirmed in polymyalgia rheumatica
name: Giant cell arteritis
label: b
answer: no
explanation: It is worth considering functional disorders, factitious disorder and malingering in any patient presenting with examination findings out of keeping with their history. However, normal power is a well-documented finding in polymyalgia rheumatica and given this patient's demographics, history and typical examination findings; polymyalgia rheumatica is the most likely diagnosis
name: Factitious disorder
label: e
answer: no

Correct answer: a