It is rare for someone to get a diagnosis of Mixed Connected Tissue Disorder (MCTD) right away. Most people bounce around from specialist to specialist, collecting diagnoses before they are finally diagnosed with MCTD. This, understandably, leads to confusion and some trust issues. How could it have taken so long to get to a diagnosis? How can you be sure it’s MCTD?
And patients aren’t the only ones confused. Doctors, especially non-rheumatologists, can be confused by MCTD, opting to use the short-hand “lupus.” In many instances, that may be ok, but for the Rheumatologist, and patient, the distinction is important.
The Imprecise Nature of Medical Science
In order to understand how and why MCTD can be confusing it is worthwhile to understand how we categorize all of our rheumatic and autoimmune conditions. In the 1950’s, an observant doctor, or doctors, began a collection of patients with similar symptoms. These patients had a butterfly shaped facial rash, hair loss, joint pain, and some went into kidney failure. The doctors cared for and studied these patients and eventually called the condition “Systemic Lupus Erythematosus.” Their research extended beyond just symptoms and included many blood studies. Through the research on their blood, the doctors found that most of the patients in their group (most, but not all) had certain autoantibodies, namely the ANA.
This research continues today. Today, instead of focusing on the presence of certain antibodies, the research is looking into the inflammatory and autoimmune pathways found in these patients. Just as with the ANA, not every patient who looks like lupus on the outside, looks the same in their immune system. This outside-in approach is the reason there are so many different types, or “flavors,” of lupus. If medical science worked in the opposite direction, if we categorized patients by the dysfunctional pathway or abnormal antibody instead of symptoms, we would end up with a group more similar than not. But, alas, that’s not the way medical science has worked.
The Original Overlap Syndrome
This story can be applied to the classification of MCTD. For many years, those with what we would now call MCTD, were considered “overlap” patients, as they seemed to have some features of lupus as well as features of scleroderma and myositis. It was the connection between the high level of the anti-RNP antibody with these patients, however, that eventually led to the MCTD classification. (This was not without drama of course, as the leading thought leaders at the time hotly debated this)
- Lupus-like: rashes, hair loss, joint pain & swelling, pleuritis
- Scleroderma-like: Raynaud’s phenomenon, skin changes, esophagus and lung changes
- Myositis-like: muscle inflammation and weakness
These symptoms morph over time. This explains why someone can initially be given a diagnosis of Lupus, only then to develop myositis and scleroderma-like skin changes and have their diagnosis change to MCTD. Was the diagnosis of Lupus wrong? Not really. I don’t think of that way…I see it as the true diagnosis hadn’t shown itself yet.
There are some clues that one can keep an eye out for in the beginning to try to avoid this initial confusion. Raynaud’s syndrome can be an early sign and warrants a closer look. Having a high anti-RNP antibody (or U1 RNP) level is another clue. The RNP antibody targets material within the nucleus, thus it is considered a type of ANA and is rarely positive if the ANA is negative. Although it is true that not every person with a RNP antibody will have MCTD, having a particularly high level should raise your suspicion.
MCTD is NOT Lupus
What does any of this matter? Who cares if we call it MCTD or lupus when many of the symptoms are the same? When we make a diagnosis, it is not only to better understand symptoms and how to best treat them, but to also have an idea of someone’s prognosis. What kind of complications should we be looking out for? The MCTD road is very different from the Lupus road. With MCTD we must keep a closer eye on the lungs, the heart and the gut. With lupus we keep vigilance over the kidneys. Our treatment choices are also different. Someone with MCTD can have a very different treatment strategy than someone with lupus or scleroderma.
Because the symptoms seen with MCTD are so varied, the treatment options are varied and need to be truly individualized. When choosing a treatment, I like to think about what symptom or what process is “driving” the condition. Is someone’s main issue inflammatory muscle disease? Lung fibrosis? Or joint pain? Each one of these problems requires a different treatment approach. And to make matters even more nuanced, the main issue can change over time. Perhaps the driver was joint pain in the beginning, then it became muscle inflammation and then lung problems. Each one of these stages requires a different approach.
MCTD, like all the autoimmune rheumatic conditions, is complex, but manageable. Understanding the basics enables you to partner with your rheumatologist to find the best treatments for you.