Cholinergic urticaria is a rare autoimmune type of allergic urticaria. Clinically characterized by acute (within an hour) rash of small itchy bubbles with serous contents in open areas of the skin. The rash tends to spread, accompanied by a prodroma. It is diagnosed on the basis of anamnesis, clinical manifestations, provocative tests for acetylcholine, artificial stimulation of an allergic reaction, blood tests for allergens, consultations of narrow-profile specialists. Treatment of cholinergic urticaria consists in neutralizing the provoking factor and correcting the concomitant pathology.
ICD 10
L50.5 Cholinergic urticaria
General information
Cholinergic urticaria is an acute itchy allergodermatosis that occurs as an immune response to the irritating effect of acetylcholine produced by the patient’s own body. In the structure of dermatological morbidity, cholinergic urticaria accounts for about 7% of all varieties of “nettle dermatoses”. Within the group, only 50% of cases of pathology reliably have autoimmune genesis, which is confirmed by the autoserum test (ASST), the mechanisms of development of the remaining 50% have not yet been definitively clarified.
The pathological process has no age, gender, seasonal framework, and is not endemic. A feature of cholinergic urticaria is the ability to control relapses taking into account the provoking factor. The urgency of the problem for clinical dermatology at the present stage is associated with the constant increase in the number of allergic dermatoses, which are the basis for the development of cholinergic urticaria, which significantly violates the quality of life of patients.
Causes
The trigger of the disease is acetylcholine, which is released by the body’s cells in response to physical exertion, stress, taking a hot bath, etc. Half of the cases of cholinergic urticaria have autoimmune genesis. Its occurrence is characterized by the constant presence in the blood of antibodies related to immunoglobulin E (IgE), which is responsible for the development of allergic reactions of the immediate type. These antibodies are located on the receptors of mast cells and constantly stimulate them, which causes the IgE-allergic mood of the patient’s body and sensitization of the skin.
The effect of provoking factors on already allergic skin causes degranulation of mast cells, which release vascular mediators, including acetylcholine. An increased amount of acetylcholine causes hypersensitivity of the immune system, provokes the development of an acute cholinergic autoimmune reaction.
The second half of cases of cholinergic urticaria develop according to an idiopathic scenario that occurs against the background of chronic diseases (pathology of the digestive tract, endocrine disorders, vegetative-vascular dystonia), stress and increased sweating. In this variant of cholinergic urticaria, the destruction of mast cells (the main effector cells of any urticaria) of unclear genesis is sufficient. Cells begin to produce histamine and prostaglandins that stimulate inflammation and activate acetylcholine, a mediator of nervous excitement, in response to which an immune response occurs, which is clinically manifested by the appearance of a rash.
Symptoms
The first clinical manifestation of the disease is acute rashes on almost unchanged, slightly edematous skin that occur within a few minutes, a maximum of an hour from the moment the patient comes into contact with provoking factors. The primary elements of cholinergic urticaria are small bubbles up to 3 mm in diameter, pale pink in the center and scarlet around the perimeter. The rash is localized on the neck, trunk and limbs, accompanied by severe itching.
Since the trigger stimulus is the “conductor” of nerve impulses acetylcholine, along with skin manifestations, symptoms of pathology of the nervous system occur: nausea, vomiting, dyspepsia, increased salivation. The temperature rises spontaneously, malaise appears, and concomitant pathology worsens.
The severity of clinical manifestations depends on the level of acetylcholine increase in the body. A distinctive feature of the clinic of cholinergic urticaria is the spontaneous rather rapid resolution of skin manifestations and other symptoms associated with direct irritation of the nervous system with a high content of acetylcholine, combined with the progression of concomitant pathology (diseases of the gastrointestinal tract, endocrine disorders).
Diagnostics
Clinical manifestations of urticaria are typical. A detailed history of the patient in combination with the symptoms is sufficient for the diagnosis of pathology by a dermatologist. The dermography of the skin and its reaction to UFOs are evaluated, pressure is applied to the skin in order to exclude physical urticaria. Confirmation of the cholinergic nature of the disease requires the use of special techniques.
- Allergy tests. The simplest diagnosis of cholinergic urticaria is with the help of provoking factors, when the patient’s hands are lowered into hot water for 2-3 minutes (> 50 degrees), which immediately causes a cholinergic response. The provocative test consists in subcutaneous administration of acetylcholine, which gives symptoms of cholinergic urticaria for 20 minutes. Skin testing by intradermal administration of autologous serum (ASST) refers to screening methods.
- Laboratory tests. Blood test, urine test, biochemical testing for C-reactive protein, parasitological examination, analysis of feces for worm eggs, a smear from the nasopharynx for an infectious onset is performed. A blood test for antinuclear antibodies is performed to exclude other types of autoimmune urticaria. Based on the data on the total amount of IgE and proteins involved in the development of allergies, chronic urticaria is excluded.
- Instrumental techniques. In difficult cases, due to the fact that cholinergic urticaria often occurs on the background of systemic diseases, skin biopsy, ultrasound of the thyroid gland and heart, EFGDS and analysis for the bacterium H. Pylori are performed with the evaluation of the results by narrow specialists.
All tests are never prescribed at the same time, the decision on the expediency of using certain techniques is made by the doctor. Cholinergic urticaria is differentiated from other types of urticaria based on the results of diagnostic tests.
Cholinergic urticaria treatment
The therapy of the disease has a cascading character and consists of several lines designed to eliminate the triggers of pathology and apply pharmacotherapy necessary taking into account the severity of clinical manifestations. The first line of treatment involves the exclusion of provoking factors (stress, alcohol, overheating) and teaching patients the correct behavior in everyday life. At this stage, first-generation antihistamines are used, including to reduce itching. A hypoallergenic diet is prescribed, concomitant diseases are corrected.
The second line of therapy for cholinergic urticaria includes the use of corticosteroids, antidepressants, sedatives, calcium channel blockers, leukotriene receptors (ALP), dietary supplements and vitamins. The third line is connected with the resistance of the pathological process to the first two, involves the use of immunomodulators and plasmapheresis, sometimes in combination with immunosuppressants. Externally, drugs containing belladonna are prescribed.
Prognosis and prevention
The prognosis is relatively favorable, taking into account the severity of the allergy and its complications. If the root cause of urticaria is not eliminated, then relapses of the disease are inevitable. Prevention of cholinergic urticaria consists in the exclusion of provoking factors.
