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Mixed connective tissue disease (Sharp’s syndrome) is a disease syndrome that combines the clinical features of lupus erythematosus, scleroderma and polymyositis, the marker of which is an antibody against nuclear ribonucleoprotein (U1RNP). The frequency of this condition is unknown and depends on the population.
What is mixed connective tissue disease?
Mixed connective tissue disease is a condition (Sharp’s syndrome) with symptoms of several systemic disorders of connective tissue, including systemic sclerosis, rheumatoid arthritis, systemic lupus erythematosus, and polymyositis or dermatomyositis. The prevalence of this condition is unknown, and it probably varies between populations. The lack of unified diagnostic criteria hampers epidemiological studies. Mixed connective tissue disease occurs in both adults and children, more often it affects the female sex (between 15 and 25 years of age).
important: Due to the fact that mixed connective tissue disease contains symptoms of several diseases – specialists argue whether it is a separate disease or the initial stage of development of specific systemic ailments.
Where does mixed connective tissue disease come from?
Unfortunately, the causes of this ailment have not been fully determined. However, there are some suspicions that mixed connective tissue disease is an autoimmune condition in which cells of the immune system hit their own body. In addition, some researchers suspect that the disease may have a genetic basis (due to the family history of the disease).
Mixed connective tissue disease – symptoms
The lesions are mainly located on the face and hands.
The main elements in the clinical picture are:
- Raynaud’s phenomenon (fingers or toes turning pale and bluish when exposed to e.g. cold temperatures)
- swelling or hardened swelling of the fingers (called sausage fingers)
- finger ulcers
- rheumatic nodules,
- maskiness or slight hardening of the skin on the face (scleroderma-like lesions),
- less frequent erythematous changes of the butterfly erythema type (as in SLE).
Skin lesions are accompanied by joint and / or muscle pain (it is very characteristic Jaccoud’s syndrome, i.e. hypertrophy in the interphalangeal joints and deviation in the metacarpophalangeal joints. In addition, individual patients are hypersensitive to light. Of the organ changes, the most common symptoms are the weakening of esophageal peristalsis and pulmonary changes, while there are no renal changes. Common symptoms include lymphadenopathy and general symptoms such as fever, fatigue and general weakness.
Diagnosis of mixed connective tissue disease
Generalized vascular proliferative changes (vasculopathia proliferativa) causing narrowing of the lumen of small arterioles are characteristic, but perivascular fibrosis is absent.
In the diagnosis of mixed connective tissue disease, general blood tests are performed. In a complete blood count in some patients leukopenia is present, hypergammaglobulinemia is characteristic, and in cases with symptoms of polymyositis, muscle enzymes may be elevated. You must also do urine test and a XNUMX-hour urine collection to determine proteinuria (differentiate from SLE) and radiological examinations (lungs, bones, esophagus, hands) and capillaroscopic examination for the differentiation with scleroderma. In rare cases, it is performed light tests.
Characteristic for mixed connective tissue disease is high titer of anti-U1RNP antibodies detected by various serological methods (IIF, ELISA, haemagglutination) (Fig. M-15). In addition, some patients have different specificity of antinuclear antibodies (Ro / SS-A, La / SSB), even without clinical signs of dryness syndrome. In some patients, rheumatoid factor is present in the serum.
In an immunopathological test, a section of unchanged skin in some cases, the presence of immunoglobulin deposits at the dermal-epidermal border (lupus band test) and in vivo bound ANA in the epidermis are found.
Mixed connective tissue disease should be differentiated from:
- systemic lupus erythematosus,
- scleroderma-like dermatomyositis,
- systemic scleroderma.
Mixed connective tissue disease – treatment
In the treatment of mixed connective tissue disease, therapy with intravenous or oral corticosteroids (encortone 20-30 mg / d) is initiated and is generally effective. The doses are high at first and then gradually taper down. In addition, patients are recommended other preparations supporting treatment.
For pain in muscles and joints, non-steroidal anti-inflammatory drugs are recommended to relieve pain. However, when it comes to swallowing disorders – proton pump inhibitors have a good effect. Patients who also struggle with pulmonary hypertension should take vascular preparations.
What is the prognosis of the disease?
The course of mixed connective tissue disease is chronic, but most patients do not develop severe organ changes. In some cases, a transition to a defined connective tissue disease (SLE, systemic sclerosis) over many years is observed, and in some patients complete recovery, allowing the withdrawal of drugs.
DIG. M-13. Mixed connective tissue disease. Scleroderma-like changes in the face.
DIG. M-14. Mixed connective tissue disease. Swelling of the fingers that mimic scleroderma.
Lit.: [1] Jabłońska S., Błaszczyk M .: Inflammatory myopathies. [In:] Hausmanowa-Petrusewicz I. (ed.): Neuromuscular diseases. Czelej Publishing House, Lublin 2005, 219-40. [2] Maddison P., Jabłońska S .: Overlap syndromes. [In:] Kater L., Baart de la Faille H. (eds.): Multisystemic autoimmune diseases. Elsevier, Amsterdam 1995, 227-40.
Source: A. Kaszuba, Z. Adamski: “Lexicon of dermatology”; XNUMXst edition, Czelej Publishing House