Critical Care Medicine-Infections and Immunologic Disease>>>>>Immunological Diseases
Question 3#

A 56-year-old woman with a history of hypertension, hyperlipidemia, mixed connective tissue disease (MCTD), and hypothyroidism presents with respiratory failure secondary to influenza A and Staphylococcus aureus pneumonia. She is admitted to the ICU for invasive mechanical ventilation.

Titers of which of the following antibodies do you most expect to be positive?

A. Anti-La
B. Anti-double stranded DNA (anti-dsDNA)
C. Anti-PR3
D. Anti-U1-ribonucleoprotein (anti-U1-RNP)
E. Antimyeloperoxidase (anti-MPO)

Correct Answer is D


Correct Answer: D

There are five diffuse connective tissue disorders (DCTDs):

  1. Systemic lupus erythematosus (SLE)
  2. Systemic sclerosis (SS)
  3. Polymyositis (PM)
  4. Dermatomyositis (DM)
  5. Rheumatoid arthritis (RA)

However, up to 25% of patients experience symptoms that may evolve from one disorder into another over time or have characteristics of several disorders at presentation, and thus are said to have an “overlap syndrome.” MCTD, also known as Sharp syndrome, is one such “overall syndrome” and shares clinical similarities with SLE, SS, and PM. Several sets of diagnostic criteria exist for MCTD, but the requirement for a positive Anti-U1-RNP antibody is universal among them. The Kasukawa criteria are one such, well-accepted, diagnostic criteria:

  1. SLE (polyarthritis, pericarditis/pleuritis, lymphadenopathy, facial erythema, or leukopenia/thrombocytopenia)
  2. SS (sclerodactyly, pulmonary fibrosis, or esophageal dysmotility)
  3. PM (proximal muscle weakness, high creatine phosphokinase, or myopathic electromyography pattern) 

Aside from musculoskeletal manifestations (above), other clinical features of MCTD include pulmonary hypertension (affecting 10%-50% patients), interstitial lung disease (ILD) (affecting 47%-78% patients), oroesophageal involvement (affecting 64% patients), cardiovascular involvement (13%-65% patients), and renal involvement (5%-36% patients).

Among the other answer choices, anti-La is seen in primary Sjogren syndrome, anti-dsDNA is seen in SLE, and anti-PR3 and anti-MPO are seen in ANCAvasculitis.


  1. Orsi D, Correa-Lopez W, Cavagnaro J. Rheumatologic and inflammatory conditions in the ICU. In: Oropello JM, Pastores SM, Kvetan V, eds. Critical Care. New York, NY: McGraw-Hill. bookid=1944§ionid=143518884. Accessed March 14, 2019.
  2. Kasukawa R. Mixed connective tissue disease. Intern Med. 1999;38:386-393.
  3. Gunashekar S, Prakash M, Minz RW, et al. Comparison of articular manifestations of mixed connective tissue disease and systemic lupus erythematosus on clinical examination and musculoskeletal ultrasound. Lupus. 2018;27:2086-2092.