Psoriatic Arthritis

The use of imaging techniques other than x-ray is not nearly as widespread for psoriatic arthritis as it is for rheumatoid arthritis, and there are no guidelines on their use in this disease, according to Dr. Philip G. Conaghan, professor of musculoskeletal medicine at the University of Leeds in England. “For the vast majority of clinicians, x-rays are still the first line of investigation.”

In part, the imaging approach is dictated by the subtype of psoriatic arthritis (PsA). For example, in the spondylitic subtype with axial involvement, the work-up would be similar to that for a patient with inflammatory back pain: x-rays of the sacroiliac joints, followed by MRI if necessary.

For peripheral PsA, x-rays of the hand joints would be performed first to detect erosions and evidence of new bone formation. “In the clear-cut patient, who's got a dactylitic digit, often imaging won't be required. You'll make a clinical diagnosis in those patients, especially if there's a history of psoriasis or nail pitting or other features that lead you to think this is a psoriatic arthritis,” he said.

There are considerably fewer data on MRI and ultrasound in PsA than in rheumatoid arthritis (RA), but “before there's any bone damage, there's soft tissue inflammation,” said Dr. Conaghan, cochair of the OMERACT (Outcome Measures in Rheumatology) MRI Inflammatory Arthritis Task Force. Imaging modalities like MRI and ultrasound that pick up soft tissue abnormalities earlier than x-ray may be more useful.

“What we see with PsA—being typically seronegative—is that a lot of that inflammation is more than just intra-articular synovitis, as we see in RA. You see a lot of extra-articular inflammation. So you find more tenosynovitis, more subcutaneous edema, and sometimes enthesitis,” said Dr. Conaghan, who contributed to the OMERACT rheumatoid arthritis MRI reference image atlas. “Both ultrasound and MRI have a role to play in managing this disease, depending on their availability at your center.” Both techniques are useful for identifying tenosynovitis and synovitis. Ultrasound allows physicians to pick up subcutaneous edema at lower levels than would be possible on a physical examination.

For MRI, sequences that pick up inflammation—gadolinium-enhanced or STIR sequences—are the most useful, said Dr. Conaghan. “For peripheral joint PsA, you could use patient-friendly extremity MRI. [Magnet strength] anywhere from 0.2 T up to 3 T could be used.”

Ultrasound and MRI are both sensitive to inflammation, but “the link between inflammation and joint damage has not been as strongly made for PsA as for RA,” Dr. Conaghan noted. Several groups are looking at clarifying this link. “Once that has been achieved, there will be more rationale for stamping out inflammation.” Researchers will need to do large randomized trials to see if the suppression of inflammation can slow structural disease progression, as it does in RA.

There are no guidelines for using MRI or ultrasound to diagnose and follow patients with PsA at the moment; current clinical practice relies on clinical markers. However, OMERACT is developing a scoring system for peripheral PsA. The largest challenge that the group faces is that “we just don't have a lot of MR data sets [on PsA] available for us to look at,” said Dr. Conaghan. “We welcome hearing from groups with such MRI sets.”

Several groups are working on scoring systems for enthesitis using both ultrasound and MRI. Some of this work will be updated at the European League Against Rheumatism congress this summer. Work on evaluating MRI for the assessment of PsA is also ongoing, but these large imaging datasets are at least 1-2 years down the road. The OMERACT scoring system may be ready for validation in the next year.

Another problem with developing imaging guidelines for PsA is that disease involvement may be much more sporadic. “So you have fewer joints to evaluate per person, meaning that you might need larger datasets to show change.”

Ultrasound and MRI are likely to be used in the future in the drug development process to show effectiveness of investigational drugs over time.

MRI with gadolinium contrast reveals dactylitis in the toe of this patient. Courtesy Dr. Philip Helliwell and Dr. Clare Groves

The use of imaging techniques other than x-ray is not nearly as widespread for psoriatic arthritis as it is for rheumatoid arthritis, and there are no guidelines on their use in this disease, according to Dr. Philip G. Conaghan, professor of musculoskeletal medicine at the University of Leeds in England. “For the vast majority of clinicians, x-rays are still the first line of investigation.”

In part, the imaging approach is dictated by the subtype of psoriatic arthritis (PsA). For example, in the spondylitic subtype with axial involvement, the work-up would be similar to that for a patient with inflammatory back pain: x-rays of the sacroiliac joints, followed by MRI if necessary.

For peripheral PsA, x-rays of the hand joints would be performed first to detect erosions and evidence of new bone formation. “In the clear-cut patient, who's got a dactylitic digit, often imaging won't be required. You'll make a clinical diagnosis in those patients, especially if there's a history of psoriasis or nail pitting or other features that lead you to think this is a psoriatic arthritis,” he said.

There are considerably fewer data on MRI and ultrasound in PsA than in rheumatoid arthritis (RA), but “before there's any bone damage, there's soft tissue inflammation,” said Dr. Conaghan, cochair of the OMERACT (Outcome Measures in Rheumatology) MRI Inflammatory Arthritis Task Force. Imaging modalities like MRI and ultrasound that pick up soft tissue abnormalities earlier than x-ray may be more useful.

“What we see with PsA—being typically seronegative—is that a lot of that inflammation is more than just intra-articular synovitis, as we see in RA. You see a lot of extra-articular inflammation. So you find more tenosynovitis, more subcutaneous edema, and sometimes enthesitis,” said Dr. Conaghan, who contributed to the OMERACT rheumatoid arthritis MRI reference image atlas. “Both ultrasound and MRI have a role to play in managing this disease, depending on their availability at your center.” Both techniques are useful for identifying tenosynovitis and synovitis. Ultrasound allows physicians to pick up subcutaneous edema at lower levels than would be possible on a physical examination.

For MRI, sequences that pick up inflammation—gadolinium-enhanced or STIR sequences—are the most useful, said Dr. Conaghan. “For peripheral joint PsA, you could use patient-friendly extremity MRI. [Magnet strength] anywhere from 0.2 T up to 3 T could be used.”

Ultrasound and MRI are both sensitive to inflammation, but “the link between inflammation and joint damage has not been as strongly made for PsA as for RA,” Dr. Conaghan noted. Several groups are looking at clarifying this link. “Once that has been achieved, there will be more rationale for stamping out inflammation.” Researchers will need to do large randomized trials to see if the suppression of inflammation can slow structural disease progression, as it does in RA.

There are no guidelines for using MRI or ultrasound to diagnose and follow patients with PsA at the moment; current clinical practice relies on clinical markers. However, OMERACT is developing a scoring system for peripheral PsA. The largest challenge that the group faces is that “we just don't have a lot of MR data sets [on PsA] available for us to look at,” said Dr. Conaghan. “We welcome hearing from groups with such MRI sets.”

Several groups are working on scoring systems for enthesitis using both ultrasound and MRI. Some of this work will be updated at the European League Against Rheumatism congress this summer. Work on evaluating MRI for the assessment of PsA is also ongoing, but these large imaging datasets are at least 1-2 years down the road. The OMERACT scoring system may be ready for validation in the next year.

Another problem with developing imaging guidelines for PsA is that disease involvement may be much more sporadic. “So you have fewer joints to evaluate per person, meaning that you might need larger datasets to show change.”

Ultrasound and MRI are likely to be used in the future in the drug development process to show effectiveness of investigational drugs over time.

MRI with gadolinium contrast reveals dactylitis in the toe of this patient. Courtesy Dr. Philip Helliwell and Dr. Clare Groves

The use of imaging techniques other than x-ray is not nearly as widespread for psoriatic arthritis as it is for rheumatoid arthritis, and there are no guidelines on their use in this disease, according to Dr. Philip G. Conaghan, professor of musculoskeletal medicine at the University of Leeds in England. “For the vast majority of clinicians, x-rays are still the first line of investigation.”

In part, the imaging approach is dictated by the subtype of psoriatic arthritis (PsA). For example, in the spondylitic subtype with axial involvement, the work-up would be similar to that for a patient with inflammatory back pain: x-rays of the sacroiliac joints, followed by MRI if necessary.

For peripheral PsA, x-rays of the hand joints would be performed first to detect erosions and evidence of new bone formation. “In the clear-cut patient, who's got a dactylitic digit, often imaging won't be required. You'll make a clinical diagnosis in those patients, especially if there's a history of psoriasis or nail pitting or other features that lead you to think this is a psoriatic arthritis,” he said.

There are considerably fewer data on MRI and ultrasound in PsA than in rheumatoid arthritis (RA), but “before there's any bone damage, there's soft tissue inflammation,” said Dr. Conaghan, cochair of the OMERACT (Outcome Measures in Rheumatology) MRI Inflammatory Arthritis Task Force. Imaging modalities like MRI and ultrasound that pick up soft tissue abnormalities earlier than x-ray may be more useful.

“What we see with PsA—being typically seronegative—is that a lot of that inflammation is more than just intra-articular synovitis, as we see in RA. You see a lot of extra-articular inflammation. So you find more tenosynovitis, more subcutaneous edema, and sometimes enthesitis,” said Dr. Conaghan, who contributed to the OMERACT rheumatoid arthritis MRI reference image atlas. “Both ultrasound and MRI have a role to play in managing this disease, depending on their availability at your center.” Both techniques are useful for identifying tenosynovitis and synovitis. Ultrasound allows physicians to pick up subcutaneous edema at lower levels than would be possible on a physical examination.

For MRI, sequences that pick up inflammation—gadolinium-enhanced or STIR sequences—are the most useful, said Dr. Conaghan. “For peripheral joint PsA, you could use patient-friendly extremity MRI. [Magnet strength] anywhere from 0.2 T up to 3 T could be used.”

Ultrasound and MRI are both sensitive to inflammation, but “the link between inflammation and joint damage has not been as strongly made for PsA as for RA,” Dr. Conaghan noted. Several groups are looking at clarifying this link. “Once that has been achieved, there will be more rationale for stamping out inflammation.” Researchers will need to do large randomized trials to see if the suppression of inflammation can slow structural disease progression, as it does in RA.

There are no guidelines for using MRI or ultrasound to diagnose and follow patients with PsA at the moment; current clinical practice relies on clinical markers. However, OMERACT is developing a scoring system for peripheral PsA. The largest challenge that the group faces is that “we just don't have a lot of MR data sets [on PsA] available for us to look at,” said Dr. Conaghan. “We welcome hearing from groups with such MRI sets.”

Several groups are working on scoring systems for enthesitis using both ultrasound and MRI. Some of this work will be updated at the European League Against Rheumatism congress this summer. Work on evaluating MRI for the assessment of PsA is also ongoing, but these large imaging datasets are at least 1-2 years down the road. The OMERACT scoring system may be ready for validation in the next year.

Another problem with developing imaging guidelines for PsA is that disease involvement may be much more sporadic. “So you have fewer joints to evaluate per person, meaning that you might need larger datasets to show change.”

Ultrasound and MRI are likely to be used in the future in the drug development process to show effectiveness of investigational drugs over time.

MRI with gadolinium contrast reveals dactylitis in the toe of this patient. Courtesy Dr. Philip Helliwell and Dr. Clare Groves