Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (8 page)

   Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are very elevated.

   Circulating immune complexes and immunoglobulin levels are higher than those found in RA.

   Peripheral blood smear review and bone marrow aspirate or biopsy may be indicated to exclude other causes of neutropenia.

MIXED CONNECTIVE TISSUE DISEASE

   Definition

   Mixed connective tissue disease (MCTD) represents an overlap syndrome with features of systemic lupus erythematosus (SLE), systemic sclerosis, and polymyositis.

   The disease can be serious with development of kidney, cardiovascular, gastrointestinal, and central nervous system manifestations. Pulmonary disease is associated with the highest mortality.

   Who Should Be Suspected?

   Presenting symptoms are often nonspecific, such as fatigue, myalgia, arthralgia, and low-grade fever. In the early stages of disease, 90% of MCTD patients have Raynaud phenomenon, arthralgia, swollen hands, fingers with “sausage-like” appearance, and muscle weakness. Other common symptoms that may develop gradually include swollen joints, esophageal dysfunction, sclerodactyly, and calcinosis.

   MCTD usually develops in the second or third decade of life, and is more common in women than men.

   Laboratory Findings

   Positive ANA, with a high-titer speckled pattern (>1:1,000 and often >1:10,000) using the indirect fluorescent antibody test (IFA).

   Presence of high titers of anti-U1 ribonucleoprotein (anti-RNP) antibodies, especially antibodies to the 68 kDa protein, is highly suggestive of an MCTD diagnosis and separates it as an independent disease.

   Anti-SSA/Ro, anti-single-stranded DNA (ssDNA), anti-Smith (Sm), and anti-double-stranded DNA (dsDNA) antibodies have also been detected, but they are not specific for MCTD.