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Mixed connective tissue disease (MCTD) is a systemic disease identified by Sharp and coworkers in 1972,1 which shows some of the clinical and pathological features of other connective tissue diseases such as systemic lupus erythematosus (SLE), systemic sclerosis (SS), and polymyositis. Although it is characterised by high concentrations of anti-U1RNP antibodies, the very definition of MCTD as a distinct entity is still under debate despite the number of immunogenetic, immunological, and clinical studies that have been carried out.2,3
Imaging of the joints in MCTD is based on traditional radiology. Features characteristic of SS (soft tissue atrophy, calcifications, tuftal resorption, distal interphalangeal joint erosions), of rheumatoid arthritis (RA) (juxta-articular osteoporosis, joint space narrowing, marginal erosions), and of SLE (joint deformities without erosions, osteonecrosis) have been described.4 Magnetic resonance imaging (MRI) is better than conventional radiology in many instances because of its multiplanar capacity and higher sensitivity.5 We describe here the MRI appearance of the hands in two patients with MCTD.
Two women, aged 32 and 25 years, were diagnosed with MCTD according to the criteria of Alarcon-Segovia and Villareal.6 Disease duration was six and 24 months, respectively. Both patients showed arthritis of the wrist and of several metacarpophalangeal (MCP) and interphalangeal joints, as well as dorsal oedema of the hands, Raynaud’s phenomenon, and xerophthalmia. Swelling of the parotid gland, myositis, and photosensitivity were present in one patient. MRI was performed using a 0.2 T dedicated MRI system (Artoscan, ESAOTE, Genova, Italy). The technical details of the sequences are given in the legend to fig 1.
Both patients with MCTD had a positive antinuclear antibody assay (titre >1/2560) and negative anti-dsDNA assay. Anti-RNP antibodies with titre >200 U/ml were found by enzyme linked immunosorbent assay (ELISA; ORGentec Diagnostica Kit, Mainz, Germany). Anti-70 kDa, -A, and -C specificity was seen by immunoblotting. Patient 1 also showed high titre anti-SSA(Ro) antibodies against 52 kDa Ro protein. Antibodies to Sm, SSB(La), topisomerase I, and Ku were absent.
Synovitis/effusion of the wrist, MCP and proximal interphalangeal (PIP) joints without erosions (fig 1) were seen in both patients with MCTD. It seemed confined to the intracapsular area in the MCP joints of patient 2 (fig 1D) but was also extracapsular in the PIP joint of patient 1 (fig 1C). In addition, tenosynovitis of the extensor and flexor tendons, and oedema of the dorsum of the hand were seen. Bone oedema, which was seen in the capitate of patient 1 (not shown) disappeared after two years’ treatment with steroids and azathioprine.
Although a few papers cite MCTD in passing among the inflammatory conditions studied by MRI,7,8 the MRI features of this disease have not been described. The most evident MRI finding in our patients with MCTD was tenosynovitis and arthritis. There were no erosions in our patients, a finding that differs from those of several radiographic studies.4 We postulate that this discrepancy may depend on the relatively early stage of MCTD in our patients. Bone oedema, an inflammatory lesion of the subchondral bone which can precede erosions in RA, was seen but reverted to normal after successful treatment. In MCTD, both intracapsular and extracapsular inflammation was observed. Oedema and inflammation of the pericapsular area is a feature which, according to a recent study,9 can be seen in seronegative spondyloarthropathies. On the contrary, it is rare in RA, a condition in which inflammation is usually confined to the articular capsule.
In conclusion, the MRI features of the hand in these two patients were not typical for MCTD alone, for they are also present in other connective tissue diseases considered in the differential diagnosis. If these findings were confirmed on a larger number of cases, however, a characteristic MRI pattern of MCTD might be identified that could prove helpful in the differential diagnosis of early patients with connective tissue diseases affecting the hand.