Rheuma Case: 57-year-old Man with Muscle Weakness

00:01 Next stop, we're gonna talk about the inflammatory myopathies.

00:04 So, here's our case. A 57-year-old construction worker with no significant past medical history presents with muscle weakness.

00:15 Now he states that he was in his usual state of health until about three to four months ago when he found that he was having trouble climbing into his truck, and even more trouble lifting equipment out of his truck. Denies any hand weakness.

00:28 Reports mild pain in his thighs.

00:30 No paresthesias but he does report some fatigue.

00:33 He smokes about half a pack per day, he drinks a 6-pack on weekends. His aunt has scleroderma.

00:39 And review of systems not much, no dyspnea, no eye symptoms, no joint pain, headaches or rashes.

00:45 So, let's highlight a few key points.

00:48 Time course, this has been going on for three or four months and has been progressive.

00:53 So, we call this is a subacute presentation.

00:56 Next up, the pattern of muscle involvement; it sounds like he's having trouble climbing into his truck which requires both legs, trouble lifting equipment which requires both arms.

01:05 It sounds like a proximal issue particularly since we've highlighted that he denies hand weakness.

01:10 So, I'd say proximal upper and lower extremities and symmetric findings.

01:15 In terms of muscle inflammation, pretty hard to say on physical exam.

01:20 We haven't actually palpated any muscles yet so we'll hold off on that one.

01:24 And then in terms of systemic involvement his review of systems was completely negative.

01:28 So, it doesn't seem like we have any systemic involvement issues at present.

01:32 Physical exam, afebrile, heart rate, and blood pressure looks okay, no lymphadenopathy.

01:39 Cardiopulmonary exam is benign. Abdomen exam is benign.

01:42 And his neurologic exam reveals symmetric 4/5 weakness to the proximal muscles in the upper and lower extremities with normal deep tendon reflexes.

01:52 And actually, on the muscle exam, no joint warmth, swelling, or tenderness.

01:57 And if we look at his skin though, there's a number of different findings here.

02:01 He's got scaling hyperkeratotic erythema on the ulnar surface of the thumb and radial surface of the second and third fingers bilaterally.

02:11 Basically, in this area of his hand.

02:13 In addition, and I think this -- we see this on the top right image there, pink papules overlying the dorsal aspects of the MCP and PIP joints symmetrically in both hands.

02:25 Next stop, we have a violaceous erythematous papulous lesion that's in a v-shaped pattern over the anterior chest and neck.

02:34 And this is of course a representative photo, not the photo of our patient.

02:37 So with that information, which of the following is the most likely diagnosis? First stop, rheumatoid arthritis.

02:46 Well he does have symmetric symptoms, he's got a rash, we can see that with rheumatoid arthritis at times.

02:52 And the family history of scleroderma, remember this are all part of the same family with rheumatoid arthritis, inflammatory myopathies, scleroderma.

03:00 So that would support the possibility of rheumatoid arthritis.

03:03 However, we're not really seeing arthritis, it's more of a myositis kind of issue.

03:09 There's myalgias going on here and some weakness.

03:11 Moreover, that's a disease more often in women but all told, I think we can leave rheumatoid arthritis on our list until we get some more serologic testing.

03:20 Next up is polymyalgia rheumatica.

03:23 This is characterized by symmetric proximal symptoms, that sounds good.

03:27 Though it's usually actually more of a pain issue than a weakness issue because despite the way that it is named, polymyalgia rheumatica is a disease of the periarticular structures not the muscles themselves.

03:39 Against this diagnosis is also that he's relatively young, we expect to see this more in folks who are in their 60s and 70s though it wouldn't be terrible atypical for his age.

03:50 And importantly, you don't see any skin findings in polymyalgia rheumatica.

03:55 So that leans us away from the diagnosis.

03:57 Nonetheless, we'll keep in it on our list for now.

04:00 Dermatomyositis, well that's characterized by symmetric proximal weakness and soreness, and skin manifestations; seems like that's our leading diagnosis so that's not going anywhere.

04:12 Next stop is including body myositis.

04:16 Well an important about this condition is you shouldn't see skin involvement.

04:20 Moreover, you tend to have more asymmetric findings -- you know, perhaps the skin involvement that he has is just work-related, you know, he does work with his hands a lot.

04:29 We'll have to keep it on the list for now until we get some more information.

04:32 Next stop, fibromyalgia. Now he's in an unusual demographic to get fibromyalgia.

04:38 It's really disease that people develop more in their 20s and 30s and it's mostly with young women.

04:44 That being said, he does have fatigue and fibromyalgia is certainly vastly more common than everything else on this list.

04:51 So we'll keep it on the list for now.

04:54 Now we haven't exactly whittled our list down very much, have we? Let's see if our laboratory data can help us out.

05:01 Alright, so a quick review here.

05:04 We've got a normal hemoglobin, a normal white count, we got a CK of 4,530, rheumatoid factor's negative, ESR of 31, mildly elevated CRP, and a very elevated ANA with a speckled pattern, as well as anti-Jo-1 antibodies. So, let's go through each one in turn then.

05:23 So, the CPK of 4,530; myopathy.

05:27 He's definitely got some sort of myositis going on with the death of a lot of myocytes.

05:31 Next stop, rheumatoid factor's negative.

05:34 Now, I'll remind you that sometimes rheumatoid arthritis can be seronegative but all told, I think this is gonna help us to take RA off the list. ESR is non-specific, the CRP is pretty non-specific.

05:46 The one thing that we can say about it is that polymyalgia rheumatica almost always has an elevated ESR and CRP.

05:53 So, it helps us to take that largely off of our list.

05:56 The ANA -- well, you'd often think of that associated with lupus, it actually also supports an inflammatory myopathy.

06:04 He's gonna need some more specific antibody testing to help to nail that in like an anti-double-stranded DNA test for example, would help to move us away from lupus.

06:13 Mind you, lupus isn't even really on our list cuz he's not the right age and gender for it.

06:17 And next stop, the anti-Jo-1 antibodies.

06:21 Well it turns out that that test indicates the presence of anti-synthetase syndrome.

06:27 What's anti-synthetase syndrome? It refers to a subgroup of patients with inflammatory myositis who specifically have evidence of autoantibodies directed against Aminoacyl tRNA synthetase enzymes which are present actually in about 30% of all cases of inflammatory myositis without dermatomyositis or polymyositis.

06:48 So why is that important? Well, it turns out that patients with anti-synthetase syndrome are much more likely to get associated interstitial lung disease so it's gonna warrant different types of screening over time, checking their PFTs and potentially a CT scan.

07:04 Lastly, in case we really needed to bring it home, we're gonna order an EMG and it's gonna show fibrillations which really supports our final diagnosis of an inflammatory myopathy.

07:14 Specifically, he's got dermatomyositis.