MCTD (Mixed Connective Tissue Disease) = Mixed (Compound) connective tissue disease (ICD-10 M 35.1)

Definition

Mixed connective tissue disease (MCTD) is a systemic connective tissue diseases with symptoms and findings also found in other connective tissue diseases such as Systemic sclerosis, Myositis, SLE og Rheumatoid arthritis (RA). MCTD can thus be perceived as an “overlap syndrome” with features from various diseases. However, genetic studies indicate that MCTD is a separate diagnosis and is separated undifferentiated connective tissue disease (reference: Flåm ST, 2015).

• For the diagnosis of MCTD is required antibody Anti-RNP is present
  

Occurrence

The prevalence (prevalence) of MCTD in Norway is 3,8 cases / 100.000 inhabitants (approx. 150 cases in Norway) (reference: Gunnarsson R, 2011).

Symptoms and findings by investigation, MCTD

• The disease often begins with Raynaud's phenomenon and swollen hands with thick fingers ("puffy hands")
• Some also get arthritis (Arthritis) rash (SLE-like) and muscle inflammation with elevated creatine kinase (CK)
• Swollen fingers ("puffy hands")
• Sclerodactylia (Tight skin on fingers)
• Myositis (Muscle inflammation)
• Arthritis (Arthritis with swelling most often in fingers)
• Anti-RNP antibody in blood sample

RNP antibody

• In a blood test are the antibodies ANA and anti-RNP present in all cases (by definition of the disease). In the most used criteria for the disease to describe the condition (Alarcon-Segovia) is required either myositis or synovitis in addition to anti-RNP antibody

General symptoms

• Exhaustion, muscle og joint painfeber tendency is common. At the same time high anti-RNP titer is a strong risk factor for the development of MCTD

Skin

• Raynaud's phenomenon, swollen fingers ("sausage fingers" / dactylitis), swollen hands with the development of tight and thickened skin (scleroderma hands).

Joint inflammation / arthritis

• Joint inflammation (arthritis) occurs at up to 60%, but not as pronounced as in Rheumatoid arthritis (RA). Arthritis is detected by rheumatological assessment, ultrasound, MRI and occasionally by x-ray examinations.

Muscle Inflammation / myositis

• Often acute start of general disease activity. Not always painful, but can typically lead to muscle weakness with reduced force in thighs and arms. The symptoms then resemble the disease Myositis. Blood test clearly shows elevated CK (creatine kinase). The symptoms have to be separated myalgia which is muscle pain without inflammatory signs and with normal CK.

Heart

• Some get rhythm changes seen on ECG. Inflammation of the pericardium (pericarditis) occur somtimes. Increased pressure in the pulmonary artery (Pulmonary hypertension) is rare (3.4%: Reference: Gunnarsson R, 2013), but serious. Symptoms of cardiac manifestations may be cardiac pains or increasing heavy breathing. Medical examination first includes auscultation. If suspected of heart disease, one will investigate further with ECG, ultrasound Doppler (echocardiography) and in some cases also with cardiac catheter examination. Cardiac effusion by MCTD occurs less frequently than with SLE, but involve the same symptoms.

Lungs

• In CT examinations, some lung changes are detected in many, but these are rarely so severe that treatment is needed

Kidneys

• Renal inflammation (glomerulonephritis) and renal impairment are quite rare. If kidney disease is detected, one should assess if the disease can be diagnosed as SLE (Systemic lupus erythematosus)

Stomach / intestinal

• Various forms of intestinal manifestations are described, but are uncommon

Nervous System

• Severe symptoms such as psychosis or seizures / epilepsy are more common in SLE, but up to 25% with MCTD experience milder symptoms including headache. Nerve pain in the form of "Trigeminus neuropathy"is reported.

Blood tests

• ANA and anti-RNP Antibodies is typical. Rheumatoid factor (RF) is also common, but non-specific (also occurs in many other conditions and among healthy ones). Low hemoglobin (anemia) is common (75%). Rapid drop in red blood cell count ("hemolysis") or low platelet count / platelet count (thrombocytopenia) is more typical of SLE. The immunoglobulin "gamma-globulin (IgG)" is often elevated. The blood drop response (SR) may be elevated even though CRP is low.

Diagnosis

The diagnosis is made by the occurrence of several typical symptoms

• Raynaud's phenomenon
• Swollen ("puffy") fingers
• RNP antibody
• Absence of SLE or other specific connective tissue disease
• Classification criteria (see below) are also often used for the diagnosis

Classification criteria

• More about criteria for MCTD classification here

Incorrect diagnosis (similar conditions, differential diagnoses)

• Read more about MCTD differential diagnoses here

Pregnancy at MCTD

There are few reported data. Complications are partly related to the antibody profile in the blood. A few have Antifosfolipid antibody and increased risk of thrombosis and spontaneous abortion. Disease activity and organ failure in the months before and during pregnancy should be under control to reduce the risk of complications. It is also important to use proper medication before and during pregnancy. Desires for pregnancy should therefore always be discussed with rheumatologists. In general, pregnancy with MCTD is perceived as a "risk pregnancy" that requires additional checks at a specialist. More about pregnancy in rheumatic diseases here

Treatment

Cortisone in the form of prednisolone is often used by high disease activity. The dose depends on whether or not the internal organs or blood cells are attacked. If pulmonary, heart or muscle inflammation is present, high starting doses may be required which will be gradually reduced. Prednisolone is often combined with Plaquenil (200-400mg / d), methotrexate (7,5-25mg / week) or Azathioprine (Azathioprine) as cortisone-saving medication. Testing with other drugs is applicable in difficult cases.

MCTD and diet

The disease progresses individually differently. Diet is not shown to affect the course. Most people with regular diets do not need special dietary measures. However, some have ailments as well Myositis and should follow the advice described there. Others with MCTD have symptoms Systemic sclerosis - or SLE- similar ailments that indicate similar measures.

Medical prognosis

MCTD is generally a milder disease than SLE og Myositis, but the individual course depends on the extent of the organ affection, and the individual response to treatment.

Investigation, Referral to specialist and Journal writing

• Keywords are listed here

Research on MCTD

It is current research on MCTD ongoing at Rheumatology Department, Rikshospitalet, Oslo which also investigates and treats most patients in Norway. A doctoral thesis has been completed (rheumatologist Ragnar Gunnarsson) and new, follow-up work has begun. Over 140 patients with MCTD participate in the department's research register NOSVAR (Norwegian Systemic connective tissue disease and vasculitis registry).

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