Undifferentiated Systemic Connective Tissue Disease (UCTD) is a autoimmune" rheumatic connective tissue disease with obvious signs of disease, but which does not quite fit in with the classic systemic connective tissue disease. Early in the course of the disease, even unclear symptoms can contribute to more Systemic connective tissue diseases: are difficult to place in a completely clear diagnosis. In undifferentiated systemic connective tissue disease, symptoms and examination findings from two or more conditions will persist without a single diagnosis being sufficient. Undifferentiated systemic connective tissue disease is thus distinguished from the following: Systemic lupus erythematosus (SLE), MCTD (mixed connective tissue disease), Sjögren's syndrome, Systemic Sclerosis, Myositis (Polymyositis, Dermatomyositis, Inclusion Legemyositis), Antisynthetase syndrome, Scleromyositis (overlap systemic sclerosis and myositis with "own" typical antibodies), Rheumatoid arthritis, Spondyloarthritis.
Approximately 25% of systemic connective tissue diseases remain unclassified over time.
Undifferentiated connective tissue disease has very typical signs of systemic connective tissue disease. These include several of the following:
- The general condition can be affected with night sweats, a little fever, poor appetite and weight loss, fatigue.
- Eczema (rash) that has no other explanation
- Swollen ("puffy") fingers
- Hair loss (alopecia), patchy or diffuse
- Joint pain (arthralgia), most often fingers
- Joint inflammation Arthritis, most often fingers
- Lung symptoms
- Systemic autoimmune connective tissue disease, often undifferentiated form, can be identified in up to 30% of newly diagnosed patients with interstitial lung disease (ILD). Distinguishing ILD associated with systemic connective tissue disease (CTD-ILD) from an idiopathic ILD such as "idiopathic interstitial pneumonia" (IIP), especially idiopathic pulmonary fibrosis (IPF), has prognostic and therapeutic consequences. Patients with CTD-ILD have a better prognosis. "Interstitial pneumonia with autoimmune features" (IPAF) is a diagnosis that lies between IIP and CTD-ILD (reference: Graney BA, 2019).
- Lymph nodes often swell
- Organ disease with symptoms from lungs, heart or kidneys
- Raynaud's phenomenon ("Fingers")
- Dry eyes and dry mouth without other explanation
Medical history with typical symptoms (see above) will give strong suspicion of a form of systemic connective tissue disease.
Clinical examination assesses joints, skin, eyes, internal organs, inclusive lungs. Measurement of tear and saliva production in case of dryness.
Blood tests may include CRP, SR, cell counts (hemoglobin, white blood cells and platelets), organ function tests (liver, kidney and metabolism tests). Antibodies as ANA (antinuclear antibody), ANCA, anti-CCP. In case of suspicion of IPAF (see lung symptoms above) one can supplement with «myositis-specific antibody». The vast majority of people with undifferentiated connective tissue disease will have a rash in ANA, elevated SR and some have too low a number of blood cells (leukopenia, thrombocytopenia, anemia). However, it is unusual with low numbers of all three cell types simultaneously.
Urine sticks (exclude egg whites / proteins and / or blood seen in nephritis)
Imaging done by symptoms from various organs. The lungs are especially important. With a normal X-ray, incipient lung changes can be easily overlooked, so CT images are preferred. Ultrasound of the heart, liver, spleen and swollen lymph nodes may be relevant for associated symptoms.
ECG can be done if signs that the heart is attacked.
Bone marrow can be examined in case of unclear condition with the possibility of leukemia, lymphoma or similar cancer.
Capillaroscopy can show signs of disease in small blood vessels
The diagnosis is most often made by a specialist in rheumatic diseases and is based on symptoms, examination findings and disease course. In undifferentiated systemic connective tissue disease, the individual variation is large within the same condition. This means that observation time over several years before the diagnosis is certain, even if one or another form of systemic connective tissue disease is detected early.
Similar conditions, differential diagnoses
Many diseases have similar symptoms and overlapping examination findings. Further investigation and observation over time exclude these:
- Other systemic connective tissue diseases (see above)
- Other Autoimmune diseases
- Auto-inflammatory disease / Periodic fever syndrome
- Inflammatory bowel disease (Ulcerative colitis, Crohn's disease)
- Painful conditions like Fibromyalgia with at the same time elevated ANA without any other signs Autoimmune disease
An individually adapted treatment is at least as relevant as with other systemic connective tissue diseases. Some do not need medication, while in others fixed use of potent drugs can prevent serious organ damage.
Some cases of undifferentiated systemic connective tissue disease develop into a classic connective tissue disease over time. However, if this has not happened during the first two years from the onset of the disease, most (approx. 65%) will remain undifferentiated (reference: Bodolay E, 2003). In general, undifferentiated systemic connective tissue disease has a good prognosis, because damage to internal organs rarely occurs. The course is nevertheless characterized by the individual symptoms.