Read Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis for Free Online
diseases are discussed elsewhere in this book.
Autoimmune disease is the pathologic result of autoimmunity, whereby the immune system attacks the person’s healthy body tissues. Autoimmunity is caused by the inappropriate activation of T cells or B cells, or both, in the absence of a definite cause. B lymphocytes can produce autoantibodies, which may interfere with a cellular function (e.g., Graves disease, myasthenia gravis) or cause tissue damage, either directly or by forming immune complexes that are deposited in tissues or blood vessels. T lymphocytes may aggregate in tissues (or a tissue) with resultant destruction.
There are more than 80 different autoimmune disorders, and more than one autoimmune disorder can be manifested by one patient. These disorders can be classified as systemic, affecting multiple organs or tissues (e.g., connective tissue autoimmune diseases such as systemic lupus erythematosus, Sjögren syndrome, or scleroderma), or organ specific, targeting one particular organ.
Multiple factors contribute to the development of autoimmune diseases:
Genetic susceptibility, mostly due to linkage to particular HLA molecules
Environmental triggers (e.g., drugs, chemicals)
Infectious agents (e.g., Mycoplasma pneumoniae , HIV)
Loss of regulatory T cells
Defects in cytokine production
ORGAN-SPECIFIC AUTOIMMUNE DISEASES
Organ-specific autoimmune diseases involve a particular organ or tissue of the body in which the target autoantigen is found. Examples of these autoimmune diseases and their target organs:
Adrenal glands (e.g., autoimmune adrenal insufficiency). See Chapter 6 , Endocrine Diseases
Bile ducts (e.g., primary biliary cirrhosis). See Chapter 5 , Digestive Diseases
Blood cells: RBC (e.g., autoimmune hemolytic anemia), WBC (e.g., autoimmune neutropenia), platelets (e.g., immune thrombocytopenic purpura). See Chapter 9 , Hematologic Disorders
Blood vessels (e.g., autoimmune vasculitis). Discussed in this Chapter and in Chapter 3 , Cardiovascular Disorders
Gastrointestinal tract (e.g., celiac disease, Crohn disease, ulcerative colitis). See Chapter 5 , Digestive Diseases
Kidney (e.g., anti–glomerular basement membrane antibody disease). See Chapter 12 , Renal Disorders
Liver (e.g., autoimmune hepatitis). See Chapter 5 , Digestive Diseases
Nervous system (e.g., myasthenia gravis [a disorder of the neuromuscular junction], multiple sclerosis, Guillain-Barré Syndrome, autoimmune autonomic failure). See Chapter 4 , Central Nervous System Disorders
Pancreas: type 1 diabetes mellitus (see Chapter 6 , Endocrine Diseases), autoimmune pancreatitis (see Chapter 5 , Digestive Diseases)
Thyroid gland (e.g., Hashimoto thyroiditis, Graves disease). See Chapter 6 , Endocrine Diseases
SYSTEMIC AUTOIMMUNE DISEASES
FELTY SYNDROME
Definition
Felty syndrome is characterized by the triad of long-standing, aggressive rheumatoid arthritis (RA), neutropenia, and splenomegaly.
It develops in a minority of patients with RA (<1%).
Who Should Be Suspected?
Patients typically present with general malaise, fatigue, loss of appetite, and unintentional weight loss. Some patients have recurrent infections, such as respiratory or skin infections, attributed to the neutropenia.
The syndrome is more common in women >30 years of age and in patients with a family history of RA.
Laboratory Findings
Neutropenia (<2,000 granulocytes/μL) is required for diagnosis. WBC count is usually <2,500/μL.
Elevated levels of rheumatoid factor (RF) and anti–cyclic citrullinated peptide (anti-CCP) antibodies (high titers).
Antinuclear antibodies (ANAs), antihistone antibodies, and antineutrophil cytoplasmic antibodies (ANCAs) are found in more than two thirds of patients.
Anti-glucose-6-phosphate isomerase antibody titer is elevated in the majority of patients.
Anemia and
Autoimmune disease is the pathologic result of autoimmunity, whereby the immune system attacks the person’s healthy body tissues. Autoimmunity is caused by the inappropriate activation of T cells or B cells, or both, in the absence of a definite cause. B lymphocytes can produce autoantibodies, which may interfere with a cellular function (e.g., Graves disease, myasthenia gravis) or cause tissue damage, either directly or by forming immune complexes that are deposited in tissues or blood vessels. T lymphocytes may aggregate in tissues (or a tissue) with resultant destruction.
There are more than 80 different autoimmune disorders, and more than one autoimmune disorder can be manifested by one patient. These disorders can be classified as systemic, affecting multiple organs or tissues (e.g., connective tissue autoimmune diseases such as systemic lupus erythematosus, Sjögren syndrome, or scleroderma), or organ specific, targeting one particular organ.
Multiple factors contribute to the development of autoimmune diseases:
Genetic susceptibility, mostly due to linkage to particular HLA molecules
Environmental triggers (e.g., drugs, chemicals)
Infectious agents (e.g., Mycoplasma pneumoniae , HIV)
Loss of regulatory T cells
Defects in cytokine production
ORGAN-SPECIFIC AUTOIMMUNE DISEASES
Organ-specific autoimmune diseases involve a particular organ or tissue of the body in which the target autoantigen is found. Examples of these autoimmune diseases and their target organs:
Adrenal glands (e.g., autoimmune adrenal insufficiency). See Chapter 6 , Endocrine Diseases
Bile ducts (e.g., primary biliary cirrhosis). See Chapter 5 , Digestive Diseases
Blood cells: RBC (e.g., autoimmune hemolytic anemia), WBC (e.g., autoimmune neutropenia), platelets (e.g., immune thrombocytopenic purpura). See Chapter 9 , Hematologic Disorders
Blood vessels (e.g., autoimmune vasculitis). Discussed in this Chapter and in Chapter 3 , Cardiovascular Disorders
Gastrointestinal tract (e.g., celiac disease, Crohn disease, ulcerative colitis). See Chapter 5 , Digestive Diseases
Kidney (e.g., anti–glomerular basement membrane antibody disease). See Chapter 12 , Renal Disorders
Liver (e.g., autoimmune hepatitis). See Chapter 5 , Digestive Diseases
Nervous system (e.g., myasthenia gravis [a disorder of the neuromuscular junction], multiple sclerosis, Guillain-Barré Syndrome, autoimmune autonomic failure). See Chapter 4 , Central Nervous System Disorders
Pancreas: type 1 diabetes mellitus (see Chapter 6 , Endocrine Diseases), autoimmune pancreatitis (see Chapter 5 , Digestive Diseases)
Thyroid gland (e.g., Hashimoto thyroiditis, Graves disease). See Chapter 6 , Endocrine Diseases
SYSTEMIC AUTOIMMUNE DISEASES
FELTY SYNDROME
Definition
Felty syndrome is characterized by the triad of long-standing, aggressive rheumatoid arthritis (RA), neutropenia, and splenomegaly.
It develops in a minority of patients with RA (<1%).
Who Should Be Suspected?
Patients typically present with general malaise, fatigue, loss of appetite, and unintentional weight loss. Some patients have recurrent infections, such as respiratory or skin infections, attributed to the neutropenia.
The syndrome is more common in women >30 years of age and in patients with a family history of RA.
Laboratory Findings
Neutropenia (<2,000 granulocytes/μL) is required for diagnosis. WBC count is usually <2,500/μL.
Elevated levels of rheumatoid factor (RF) and anti–cyclic citrullinated peptide (anti-CCP) antibodies (high titers).
Antinuclear antibodies (ANAs), antihistone antibodies, and antineutrophil cytoplasmic antibodies (ANCAs) are found in more than two thirds of patients.
Anti-glucose-6-phosphate isomerase antibody titer is elevated in the majority of patients.
Anemia and