Page 94 - Textbook of Pathology, 6th Edition

78 activities may lead to high levels of auto-antibody production  TABLE 4.8: Autoimmune Diseases.
by B cells contributing to auto-immunity.
ORGAN NON-SPECIFIC (SYSTEMIC)
iv) Fluctuation of anti-idiotype network control may cause failure
of mechanisms of immune tolerance. 1. Systemic lupus erythematosus*
2. Rheumatoid arthritis
v) Sequestered antigen released from tissues. ‘Self-antigen’ 3. Scleroderma (Progressive systemic sclerosis)*
which is completely sequestered may act as ‘foreign-antigen’ 4. Polymyositis-dermatomyositis*
if introduced into the circulation later. For example, in trauma 5. Polyarteritis nodosa (PAN)
to the testis, there is formation of anti-sperm antibodies 6. Sjögren’s syndrome*
against spermatozoa; similar is the formation of 7. Reiter’s syndrome*
SECTION I
autoantibodies against lens crystallin. 8. Wegener’s granulomatosis
2. Genetic factors. There is evidence in support of genetic ORGAN SPECIFIC (LOCALISED)
factors in the pathogenesis of autoimmunity as under:
1. ENDOCRINE GLANDS
i) There is increased expression of Class II HLA antigens on (i) Hashimoto’s (autoimmune) thyroiditis
tissues involved in autoimmunity. (ii) Graves’ disease
ii) There is increased familial incidence of some of the (iii) Type 1 diabetes mellitus
autoimmune disorders. (iv) Idiopathic Addison’s disease
2. ALIMENTARY TRACT
3. Microbial factors. Infection with microorganisms, (i) Autoimmune atrophic gastritis in pernicious anaemia
particularly viruses (e.g. EBV infection), and less often (ii) Ulcerative colitis
bacteria (e.g. streptococci, Klebsiella) and mycoplasma, has (iii) Crohn’s disease
been implicated in the pathogenesis of autoimmune diseases. 3. BLOOD CELLS
However, a definite evidence in support is lacking. (i) Autoimmune haemolytic anaemia
(ii) Autoimmune thrombocytopenia
TYPES AND EXAMPLES OF AUTOIMMUNE DISEASES (iii) Pernicious anaemia
4. OTHERS
Depending upon the type of autoantibody formation, the
autoimmune diseases are broadly classified into 2 groups: (i) Myasthenia gravis
(ii) Autoimmune orchitis
1. Organ specific diseases. In these, the autoantibodies (iii) Autoimmune encephalomyelitis
formed react specifically against an organ or target tissue (iv) Goodpasture’s syndrome
General Pathology and Basic Techniques
component and cause its chronic inflammatory destruction. (v) Primary biliary cirrhosis
The tissues affected are endocrine glands (e.g. thyroid, (vi) Lupoid hepatitis
pancreatic islets of Langerhans, adrenal cortex), alimentary (vii) Membranous glomerulonephritis
tract, blood cells and various other tissues and organs. (viii) Autoimmune skin diseases
2. Organ non-specific (Systemic) diseases. These are *Diseases discussed in this chapter.
diseases in which a number of autoantibodies are formed
which react with antigens in many tissues and thus cause 2. Discoid form is characterised by chronic and localised
systemic lesions. The examples of this group are various skin lesions involving the bridge of nose and adjacent cheeks
systemic collagen diseases. without any systemic manifestations. Rarely, discoid form
However, a few autoimmune diseases overlap between
these two main categories. may develop into disseminated form.
Based on these 2 main groups, a comprehensive list of ETIOLOGY. The exact etiology of SLE is not known.
autoimmune (or collagen) diseases is presented in Table 4.8. However, autoantibodies against nuclear and cytoplasmic
Some of the systemic autoimmune diseases (marked with components of the cells are demonstrable in plasma by
asterisk) are discussed in this chapter while others from both immunofluorescence tests in almost all cases of SLE. Some
the groups are described later in the relevant chapters. of the important antinuclear antibodies (ANAs) or antinuclear
factors (ANFs) against different nuclear antigens are as
Systemic Lupus Erythematosus (SLE) under:

SLE is the classical example of systemic autoimmune or i) Antinuclear antibodies (ANA) are the antibodies against
collagen diseases. The disease derives its name ‘lupus’ from common nuclear antigen that includes DNA as well as RNA.
the Latin word meaning ‘wolf’ since initially this disease was These are demonstrable in about 98% cases and is the best
believed to affect skin only and eat away skin like a wolf. as screening test.
However, now 2 forms of lupus erythematosus are described: ii) Antibodies to double-stranded (anti-dsDNA) is the most
1. Systemic or disseminated form is characterised by acute specific for SLE, especially in high titres, and is present in
and chronic inflammatory lesions widely scattered in the 70% cases.
body and there is presence of various nuclear and iii) Anti-Smith antibodies (anti-Sm), in which antibodies
cytoplasmic autoantibodies in the plasma. appear against Smith antigen which is part of