SLE and RA?

[soxman]

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It seems like both SLE and RA pretty much can have the same manifestations. Both are autoimmune and can target the same organ systems. Is detecting anti smith and anti dsDNA, etc for SLE the only way to differentiate the two?

 

[Ronin786]

Look for the SLE associated rashes (discoid, malar, photosensitivity). Also non-deforming joint pain.

RA is more joints and kidney, whereas SLE is likely to involve everything.

 

[gravitywave]

Clinically they are typically quite different. yes RA can have systemic manifestations but usually the picture is overwhelmingly one of symmetric small joint arthritis. SLE is by definition a multiorgan system disease and if there is joint involvement it more often tends to be arthralgia.

Serology informs rheumatologic diagnoses but it's often unlike most of the rest of medicine where lab tests are usually interpreted as confirmatory.

 

[gravitywave]

Look for the SLE associated rashes (discoid, malar, photosensitivity). Also non-deforming joint pain.

RA is more joints and kidney, whereas SLE is likely to involve everything.

heart, eyes, and lungs before kidney in RA. I don't remember CKD being a big part of RA, whereas SLE glomerulonephritis is definitely huge

 

[Ronin786]

heart, eyes, and lungs before kidney in RA. I don't remember CKD being a big part of RA, whereas SLE glomerulonephritis is definitely huge

Thats probably true. I'm just fresh off a Uworld, Amyloidosis/RA question so thats probably why.

 

[gravitywave]

Thats probably true. I'm just fresh off a Uworld, Amyloidosis/RA question so thats probably why.

yeah you're absolutely right but the others are more common. I had to look it up, amyloidosis is one of the most common systemic causes of the nephrotic syndrome but it's only clinically relevant in 1-2% of RA patients. Which means it's still more common than Felty's, which is definitely rare but for some reason that's the one everyone remembers. The one I always think of anyway 🙄

 

[soxman]

thanks guys! makes better sense now

 

[Ronin786]

yeah you're absolutely right but the others are more common. I had to look it up, amyloidosis is one of the most common systemic causes of the nephrotic syndrome but it's only clinically relevant in 1-2% of RA patients. Which means it's still more common than Felty's, which is definitely rare but for some reason that's the one everyone remembers. The one I always think of anyway 🙄

I didn't expect Felty's to show up, but I ran into it on an NBME I took the other day.

Thats just the name of the USMLE, testing whats obscure over whats common.