INTRODUCTION : Overlap syndrome is defined in a patient when a combination of more than one
major feature of connective tissue disease is present with a specific serological test1. The
common symptoms of overlap syndrome include sclerodactyly, arthritis and Raynaud’s
phenomenon. A distinguishable feature in patients with autoimmune disease is the
presence of non organ specific auto antibodies to RNA, DNA and to proteins that bind
them. For MCTD the well known serological marker is anti U1RNP antibody.
The ribonuclear proteins are auto antigens located on small nuclear RNP
particles. They are uridine rich. The major action is splicing of pre messenger RNA. Anti
U1RNP is associated with features of scleroderma, including Raynaud’s phenomenon.
There has been a close association of anti U1RNP antibody with pulmonary fibrosis and
negative correlation with renal involvement.
MCTD, although an overlap syndrome, does not have any distinctive clinical
feature. The components of MCTD (systemic sclerosis, systemic lupus erythematosus
and idiopathic inflammatory myositis) do not occur simultaneously but consecutively
over years. Raynaud’s phenomenon occurs in almost all patients with MCTD.
AIMS AND OBJECTIVES : 1. To correlate anti U1RNP antibody with the clinical spectrum of Mixed connective tissue disease (according to Kasukawa’s criteria) and Overlap Syndrome.
2. To analyse the association of anti U1RNP antibody with the pulmonary
manifestations among Mixed connective tissue disease and Overlap Syndrome.
MATERIALS AND METHODS : All patients who satisfied the inclusion criteria were chosen and a detailed history was obtained and complete clinical examination was done. All the enrolled patients were
subjected to laboratory investigations (haemogram, biochemical parameters and urine
routine), Electrocardiogram, Echocardiography, Ultrasonogram, Upper
gastrointestinalscopy and Immunological investigations (C-reactive protein, Rheumatoid
factor, anti nuclear antibody and ANA profile 3). Chest x-ray, high resolution
computerised tomogram of the chest and pulmonary function tests were done to asses
pulmonary involvement of the cases under study. ANA profile 3 was done using Immunoblot method.
Inclusion Criteria: Patients with clinical features suggestive of overlap syndrome (systemic lupus
erythematosus, systemic sclerosis and myositis) and mixed connective tissue disease were included.
Exclusion Criteria: 1. Patients with well defined isolated connective tissue diseases like
Rheumatoid arthritis, Systemic lupus erythematosus, Systemic sclerosis,
Idiopathic inflammatory myositis, Sjogren’s syndrome.
2. Children below 16 yrs. Descriptive statistical analysis has been carried out in the present study. Results on continuous measurements are presented on Mean SD and results on categorical
measurements are presented in percentage. Chi-square test has been used to find the
significance of study parameters on categorical scale between two groups. All analyses
were two tailed and p<0.05 was considered significant. SPSS version 16.0 was used for
data analysis.
RESULTS : Most number of patients are between second and third decade. Proportion of females with overlap syndrome/mixed connective tissue disease was higher and the ratio of females to males was 20.3:1. Percentage of anti U1RNP antibody positivity was 79.1% and 20.9% of patients
were found to be negative for anti U1RNP. Mixed connective tissue disease - 58.14% (n=25),
Systemic sclerosis/myositis - 25.58% (n=11), Systemic sclerosis/SLE - 11.66% (n=5),
SLE/myositis - 4.66% (n=2). 50% of patients with Overlap Syndrome are positive for anti U1RNP antibody. ILD is more common among MCTD patients compared to Overlap syndrome. The prevalence of
PHT is almost equal in both the groups. Raynaud’s phenomenon, the commonest and renal involvement, the least common manifestation in MCTD patients. Arthritis is the commonest feature and renal manifestations scored the least, among Overlap Syndrome group. Proportion of arthritis is higher in anti U1RNP positive group compared to anti U1RNP negative group (91.2% Vs 77.8%) though statistically insignificant (p
value>0.05). CONCLUSION : Mixed connective tissue disease and Overlap Syndrome is more common among
females.
Second and third decades are the susceptible age group for MCTD and Overlap
Syndrome.
Arthritis is the most prevalent symptom among the anti U1RNP antibody positive
Overlap Syndrome group.
Raynaud’s phenomenon is the most common clinical feature of MCTD.
Statistically significant association was found between Raynaud’s phenomenon
and anti U1RNP antibody positivity (p value <0.05).
Puffy hands, sclerodactyly and myositis are proportionately higher in anti
U1RNP antibody positive group of MCTD and Overlap Syndrome (statistically
not significant p value>0.05).
Interstitial lung disease is more common among anti U1RNP antibody positive
patients in both MCTD and Overlap Syndrome (statistically not significant p
value>0.05).
Renal manifestations are uncommon in both MCTD and Overlap Syndrome
patients.
Renal involvement and PHT had no association with the presence of anti U1RNP
antibody
