Journal of Postgraduate Medicine Medknow Publications and Staff Society of Seth GS Medical College and KEM Hospital, Mumbai, India ISSN: 0022-3859 EISSN: 0972-2823 Vol. 51, Num. 2, 2005, pp. 108-108

Journal of Postgraduate Medicine, Vol. 51, No. 2, April-June, 2005, pp. 108

Expert's Comments

Delayed development of pulmonary hypertension in mixed connective tissue disease

Greidinger Eric L.

University of Miami Miller School of Medicine and VAMC, 1400 NW 10th Avenue, Suite 602, Miami, FL 33136

Correspondence Address: University of Miami Miller School of Medicine and VAMC, 1400 NW 10th Avenue, Suite 602, Miami, FL 33136, egreidinger@med.miami.edu

Code Number: jp05041

The paper, "Pulmonary hypertension not a major feature of early mixed connective tissue disease: A prospective clinicoserological study" published in this issue describes the clinical manifestations of 13 recently diagnosed patients who satisfy standard classification criteria for Mixed Connective Tissue Disease (MCTD), from a cohort of 1500 patients seen at a rheumatology referral centre in India between 2002 and 2004.[1] Consistent with prior reports that go on to find that it is ultimately the leading cause of death from MCTD,[2] the authors find that pulmonary hypertension is seldom present early in the course of MCTD.

Since the immune response in MCTD has been found to evolve over time,[3] one potential explanation for the late and inconsistent development of pulmonary hypertension in MCTD is that anti-lung autoimmunity emerges late in the course of the disease. Reactivity between some RNP autoantibodies (and other MCTD-associated autoantibodies) and the respiratory tract has been observed.[4] T cell infiltrates are also seen at sites of MCTD end organ injury including the lung.[5] The specificities and evolution of any such anti-lung-specific response in MCTD remain to be further defined, however.

The recent development of an animal model of MCTD-like perivascular and interstitial lung disease after immunization with an RNP peptide may lead to further insights.[6] In the mouse model, as has been reported in humans,[7] perivascular pulmonary inflammatory infiltrates can be observed frequently, even in the absence of clinical evidence of pulmonary hypertension, and even at time points early in the disease. Thus, although a lag exists between the clinical expression of pHTN and other MCTD manifestations, this may be attributable to the extent of lung injury that must occur before pHTN becomes clinically apparent, as opposed to possible delays in the development of an anti-lung-specific component of the MCTD immune response.

As their number and duration of follow-up grows, it will be of relevance to continue to compare the manifestations, pulmonary and otherwise, seen in this cohort of Indian MCTD patients to those reported in other ethnic groups. Thus far, it is remarkable that across multiple ethnic groups and multiple investigators, the prevalence of individual clinical manifestations in MCTD seems generally similar (at least given the wide confidence intervals that small sample sizes bring). This suggests that MCTD seen around the world is likely to be linked by common pathophysiology. If pHTN remains less common in Indian patients than has been reported in Caucasian and Japanese cohorts over time,[2],[7] immunologic and genetic studies of this group may help elucidate the factors leading to pHTN in MCTD. Thus, findings from this new cohort in India are likely to continue to be of interest to the worldwide MCTD community.

REFERENCES

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