The signs and symptoms of some dermatologic and rheumatologic diseases sometimes overlap, and a better understanding of their associations and subsequent clinical and laboratory evaluations can help in optimizing the treatment and management of this patient population.
AAD San Francisco – Patients with certain dermatologic diseases may often have an overlap with rheumatologic symptoms and diseases, with the most important associations found among the connective tissue disorders including lupus erythematosus, dermatomyositis, and vasculitides, as well as patients with inflammatory arthritides such as rheumatoid arthritis and psoriatic arthritis (PsA). A better understanding of these disease associations and how to best approach patients with these comorbidities can help clinicians in optimally treating and managing this patient population.
Given this increasingly recognized overlap of dermatologic and rheumatologic diseases seen in dermatologic patients, dermatologists often find themselves at the front line of screening patients for systemic rheumatic conditions. In example, cutaneous lupus is the second most common first presenting sign of systemic lupus erythematosus (SLE) and may therefore first present to the dermatologist. In addition, it has been estimated that upwards of 30% of patients with psoriasis will go on to develop psoriatic arthritis. The dermatologist is in an important and unique position to screen the patient with psoriasis for underlying psoriatic arthritis symptoms.
The many faces of overlap between dermatology and rheumatology demonstrated by cutaneous and related systemic findings. Photo credit: Joseph F. Merola, M.D.
According to one expert, the areas where dermatologists should become more familiar with in order to better treat and manage patients with overlapping dermatologic and rheumatologic signs and symptoms include
“It has been my experience that some dermatologists feel uncomfortable in these three areas when evaluating the patient with skin findings that may have underlying systemic rheumatic disease. Having been through dermatology training first, I myself was not always comfortable with the approach to differentiating degenerative arthritis from inflammatory arthritis. Under the umbrella of inflammatory arthritis, we are including diseases like rheumatoid arthritis and in this case, most importantly probably for the dermatologist, psoriatic arthritis,” says Joseph F. Merola, M.D., MMSc, board certified dermatologist, internist and rheumatologist, assistant professor at Harvard Medical School, director of the Center for Skin and Related Musculoskeletal Diseases, and director of clinical trials at Brigham and Women’s Hospital in Boston.
In an attempt to help dermatologists distinguish and remember the signs and symptoms of inflammatory arthritis and psoriatic arthritis, Dr. Merola and colleagues recently published a paper with the useful acronym mnemonic “PSA”:
Pain (in the joints)
Stiffness (>30 minutes after a period of inactivity)/sausage digit (dactylitis)
Axial (axial spine involvement/back pain associated with stiffness and pain that improves with activity).1
“Patients presenting with psoriasis and/or a strong family history of psoriasis together with at least 2 of the PSA items would have a higher than average chance of a PsA diagnosis. While we appreciate the oversimplification of this short mnemonic, we hope that it will serve to increase a basic awareness of PsA, emphasize some of its core features, and facilitate the rapid screening of psoriasis patients. Hopefully, the mnemonic will prompt the use of further validated screening tools and/or trigger a referral to a rheumatologist, if needed,” Dr. Merola says.
Some of the symptoms that help to distinguish between inflammatory from non-inflammatory arthritis symptoms include joints that get red, hot, swollen and tender-essentially, all of the signs associated with inflammation. In addition, Dr. Merola says that stiffness, particularly after a period of inactivity, is another symptom that can help direct the clinician towards an accurate diagnosis of inflammatory arthritis. Here, patients will typically have trouble moving after a period of inactivity such as sitting at a desk or sitting with their legs crossed for 30 minutes or more.
The stiffness is due to a so-called ‘gelling’ phenomenon, Dr. Merola says, where the joints gel or get stiff after a period of inactivity. Interestingly, this stiffness will improve with activity in patients with inflammatory joint disease but not typically in patients with wear and tear of osteoarthritis. This would be a helpful tip to discern between the two types of arthritis. Another symptom that can help discern between inflammatory from non-inflammatory arthritis is fatigue. According to Dr. Merola, a lot of patients with these conditions will often complain of fatigue, a common symptom seen in connective tissue and inflammatory diseases.
“Fatigue is something I think we often overlook because we think we are all tired after work, but these patients are usually significantly more tired than healthy individuals. In my experience, fatigue or severe fatigue should not be underestimated in affected patients,” Dr. Merola says.
According to Dr. Merola, a thorough ‘Review Of Systems’ (ROS) should address all of the questions that one might ask in a general review of systems that is rheumatology-based or in a rheumatology setting. For example, in discoid lupus patients where the clinician wants to rule out whether or not they have systemic lupus erythematosus, the clinician must be wary to ask the patient of systemic symptoms, such as sicca symptoms, including dry mouth, dry eye or muscle weakness. It is often most helpful to inquire about these symptoms as they relate to daily function (for example, are patients able to make saliva, eat a cracker without a glass of water nearby, rise from a seated position without using their arms for help, etc.). The ROS is helpful in teasing out the possibility of underlying systemic features of disease.
Ordering the appropriate serologic tests and correctly interpreting the results is another key step in helping the clinician to hone in on the accurate diagnosis in overlap patients. Most of the diagnoses made by clinicians are ultimately clinical diagnoses, Dr. Merola says, supported by laboratory, radiologic and other testing. According to Dr. Merola, one of the more common referrals he sees in his role as a Rheumatologist is the evaluation of a patient with a ‘positive’ ANA test.
“It is important to remember that the ANA test is only useful in the context of the clinical presentation of the patient and that a positive test depends on many factors, including the serum dilution used for testing and the age of the individual. For example, up to 30% of randomly selected healthy individuals have a positive ANA at a serum dilution of 1:40, 13% at 1:80 and 3% at 1:320,” Dr. Merola says.
It is also important to remember that there are many other reasons that a patient may have a positive ANA outside of a connective tissue disease diagnosis, Dr. Merola says, including other autoimmune diseases such as thyroid disease, infections such as viral hepatitis, neoplastic conditions, and medications, as well as having a first-degree relative with an autoimmune disorder. Clinicians should also keep in mind the diagnostic benefits of a simple urinalysis when evaluating their patients, as it is one of the most useful and inexpensive screening tests in the SLE patient to detect early nephritis. In addition, Dr. Merola says that a small number of patients with a negative ANA may still have a positive anti-Ro/SSA antibody (<5%). If there is a high suspicion for SCLE (subacute cutaneous lupus erythematosus), for example, this antibody may be ordered separately from a screening ANA test.
According to Dr. Merola, a team approach and close working relationship between the dermatologist and the rheumatologist is key to the complete treatment of patient with cutaneous and systemic rheumatologic disease.
“It is not uncommon that dermatologists and rheumatologists consult on their overlap patients. Interestingly, there are a number of centers in the country such as ours that have put together combined clinics where the dermatologist and rheumatologist see these patients jointly. This is a really unique model considering how much overlap there is, which further underscores the frequency of comorbidities seen in this patient population. These clinics also offer a unique training opportunity for trainees. As we learn more and more about other comorbid conditions such as cardiovascular disease and the metabolic syndrome, dermatologists will have to become increasingly comfortable with co-managing patients with these other specialties,” Dr. Merola says.
Dr. Merola has no relevant disclosures.
1. Cohen JM, Husni ME, Qureshi AA, Merola JF. Psoriatic arthritis: it's as easy as "PSA". J Am Acad Dermatol. 2015;72(5):905-6.