Organ specific autoimmunity

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Requests for “autoimmune screen” are not acceptable.

Requests should be for specific autoantibodies as indicated by the history.

Patient information is also available from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)

Thyroid goitre/nodule, hypo/hyperthyroidism

The levels of antibodies to thyroid peroxidase are closely related to the degree of lymphocytic infiltration in the thyroid. They are raised in autoimmune thyroiditis (90% of hypo-, >60% of hyper-) and both in post-viral and post-partum thyroiditis. They are less frequently raised in thyroid neoplasia/nodules/cysts, but their presence does not exclude these conditions.

Adrenal failure and gonadal failure

Relevant immunological tests:

In this country, Addison’s disease is most often due to autoimmunity; the presence of antibodies to adrenal cortex suggests an autoimmune cause. There may also be antibodies to steroid producing cells of ovary and testis.

A small proportion of cases of premature menopause are due to autoimmune oophoritis. Some of these patients also have adrenal failure – the same tests are done for both.

Polyendocrine autoimmunity

Relevant immunological tests:

In addition:

Type 1: Usually presents under 10 yrs old, m=f. Hypoparathyroidism, adrenal failure and candidiasis also hepatitis, alopecia, delayed puberty, etc.

Type 2: Occurs in adolescence/early adulthood, f>m, Addison’s + thyroid failure + type 1 diabetes mellitus M – maybe gonadal failure, vitiligo.

Type 3: Generally older, f>>m, autoimmune thyroiditis together with diabetes mellitus, gastric autoimmunity (GPC, anti-IF) – maybe other such as myasthenia.

The spectrum of results may help confirm the diagnosis.

Liver autoimmunity

Relevant immunological tests:

Primary biliary cirrhosis (PBC) and autoimmune chronic active hepatitis (CAH) are associated with characteristic autoantibodies that are helpful in classifying the hepatitis and separating autoimmune CAH from the other forms.

Patterns may include antibodies to smooth muscle (actin), reported as SMA-T in CAH, liver/kidney microsomal antibodies in LKM-positive autoimmune hepatitis and antibodies to mitochondria PBC.

Centromere antibodies are also found in some cases of primary biliary cirrhosis. Presence of autoantibodies does not exclude a viral cause for the hepatitis.

Because of the overlap between various different forms of hepatitis, it is usually best to test for all the types of autoantibody – AMA, SMA, LKM and ANA. There is a polyclonal increase in immunoglobulins in autoimmune and viral hepatitis, whilst a raised IgM is seen in primary biliary cirrhosis. Serum electrophoresis may reveal lack of alpha-1-antitrypsin if this is associated with the cirrhosis.

Primary sclerosing cholangitis has no definitive serological markers, but may be associated with ANCA (anti-neutrophil cytoplasmic antibodies) or ANA or SMA.

Pemphigus/pemphigoid

Relevant immunological tests:

Blistering skin conditions may involve autoimmunity – antibodies are found to the epidermal intercellular “cement” in pemphigus, and to the epidermal basement membrane in pemphigoid.

The pemphigus-like pattern is also seen in some patients with leprosy, burns, penicillin rashes, SLE, MG with thymoma, dermatomycoses, erythema multiforme, etc – that of pemphigoid in herpes gestationis and epidermolysis bullosa acquisita.

Dermatitis herpetiformis (DH)

Relevant immunological tests:

Though the diagnosis of DH is based on the appearance of the rash and IgA in the dermo-epidermal junction in the dermal papillae in biopsies, the presence of IgA antibodies to tTG may point to the association of DH with gluten sensitivity (see Coeliac disease).

Dressler’s syndrome, post cardiotomy syndrome

Relevant immunological test: Cardiac muscle antibodies

Post-myocardial injury syndromes, including Dressler’s syndrome, are associated with the presence of anti-myocardial antibodies, which reflect the degree of cardiac damage.

 

(Last reviewed January 2020)