Allergic drug rash
This is one of the most diverse and common types of drug rashes. According to its incubation period, development, rash manifestation and regression, it can be divided into at least 10 subtypes, such as erythema fixum, scarlet fever-like erythema, measles-like erythema, urticaria-like, erythema multiforme, erythema nodosum, pityriasis, purpura and maculopapular epidermal necrolysis loosening.
The following are a few representative subtypes.
1, fixed erythema (fixed rash): is the most common kind of drug rash, according to statistics, accounting for 22%-44% of drug rash, 909 cases of drug rash in this section have 318 cases of this form, accounting for 34, 98%, the common causative drugs are sulfonamides (long-acting sulfonamides in the first place), antipyretic and analgesic drugs, tetracyclines and sedative edematous patches, round or oval, clear edges, one to several blisters on the heavy spots or large blisters. The erythema varies from one to several patches and is asymmetrical in distribution. It can occur in any part of the body, often at the junction of skin and mucous membrane, such as the mouth and lips and external genitalia, and often causes erosion due to friction. In case of recurrence, the lesions usually remain in the same place and completely or partially overlap with the previous pigmented spots, and often expand and increase compared with the previous one. The lesions may be locally itchy, with varying degrees of fever between those with extensive lesions. After the erythema fades, it often leaves a bright purple-brown pigmented spot, which does not fade away for many years and has diagnostic value. A few edematous erythema without purple color will fade quickly and can leave no trace. Individual cases can be accompanied by erythema multiforme-like, urticaria-like or measles-like erythema.
2. Scarlet fever-like erythematous rash: It occurs suddenly, often accompanied by chills, fever (above 38℃), headache, and general malaise. The rash starts as large or small erythematous patches, developing from the face and neck, trunk, upper extremities to lower extremities, and can spread over the whole body in 24 hours, with symmetrical distribution and edematous, bright red color, which can be decolored by pressure. Later, the rash increases and expands, fusing with each other, and can involve the entire skin, similar to scarlet fever. However, the patient is generally well and does not have the other manifestations of scarlet fever. After the development of the rash reaches its climax, the redness and swelling gradually disappear, followed by large flakes, and after the body temperature, the scales gradually become thinner and thinner and less, resembling chaffing, and the skin returns to normal, the whole course of the disease does not exceed one month, and there is usually no visceral damage. If the rash like measles, it is called pityriasis rosea-shaped drug rash; the rest of the analogy.
3.Severe polymorphic erythema: this is a serious herpetic polymorphic erythema, in addition to skin damage, eyes, mouth, external genitalia and other serious mucosal damage, there are obvious vesicles, exudate. It is often accompanied by chills and high fever. It can also be complicated by bronchitis, pneumonia, pleural effusion and kidney damage. Eye damage can lead to blindness. This type of drug rash is more common in children. It is important to note, however, that this syndrome is sometimes not caused by drugs.
4. Herpetic epidermal necrolysis-loosening drug rash: clinically rare, but quite serious. The onset is rapid and the rash spreads throughout the body within 2-3 days. The initial bright red or purplish-red spots. Sometimes the rash starts as a polymorphic erythema, and later increases and expands, fusing into a brownish-red swath. In severe cases, the mucous membranes are involved at the same time, and the body can be described as incomplete. Large patches of flaccid blisters appear, forming many parallel folds 3-10 cm long, which can be pushed from one place to another. The epidermis is extremely thin and can be broken with a slight rubbing, showing a clear loosening of the spinous layer. The whole body is often accompanied by high fever of about 40℃. In severe cases, the stomach, intestines, liver, kidneys, heart and brain can be involved simultaneously or sequentially. A case of death due to this disease was seen in which the wall of the nasal feeding tube was densely covered with detached mucosa. The course of the disease is somewhat self-limiting, and the rash often begins to subside after 2-4 weeks. In case of serious complications or severe involvement of some important organs, or due to improper management, death can occur in about 2 weeks.
The etiology of other types of drug rashes and drug reactions is not fully understood. There are many types, the main ones are described below.
1, generalized exfoliative dermatitis type
It is one of the more serious types of drug rash, second only to the severity of herpetic epidermal necrolysis loosening drug rash, in the absence of corticosteroids years, its high mortality rate. Because of the high dose or long course of drugs used to cause this type of rash, there may be a combination of toxic reactions on top of allergic reactions. The disease is characterized by a long incubation period, often more than 20-20 days, and a long course, usually at least one month. The entire course of the disease can be divided into 4 stages.
(1) The prodromal phase, manifested as a transient rash, such as symmetrical erythema confined to the chest, abdomen or femur, with self-pruritus, or with fever, which is a warning symptom and may be avoided if the drug is discontinued at this time.
(2) The rash may develop slowly and gradually from the face downward, or start as an acute attack, and later the rash may spread to the whole body quickly or slowly. At the climax of the rash attack, the skin is bright red and swollen, with significant facial edema, often with overflowing crusts, accompanied by chills and fever. Some patients may develop internal organ damage such as liver, kidney and heart. The total white blood cell count of peripheral blood picture is mostly increased, usually between 15×109-20×109/L (15000-20000/mm3).
(3) Exfoliation phase, which is the characteristic manifestation of the disease. The redness of the rash begins to subside, followed by fish scale to large flakes, scales can be covered with sheets, hands like wearing broken gloves, feet like wearing broken socks, and repeatedly shed, lasting from one to several months. Hair and finger (toe) nails often fall off at the same time.
(4) In the recovery period, ichthyosquamous desquamation or furfuraceous, then gradually disappear, and the skin returns to normal. Since the application of corticosteroids, the course of the disease can be significantly shortened, the prognosis is also greatly improved.
2.Short course antimony dermatitis type
(1) high prevalence, generally in 30-40% or more, some can be as high as 60-70%.
(2) short incubation period, all within 2-3 days after the start of treatment.
(3) The rash develops after the antimony dosage reaches 0.3g.
(4) It is common in summer.
(5) The rash is symmetrically distributed on the face, neck, back of hands and fingers, occasionally on the chest and abdomen, resembling prickly heat, dense but not fused, with a mild inflammatory response, a slight itching or burning sensation, and some systemic symptoms such as fever.
(6) The course of the disease is self-limiting, even if the drug is not stopped, the rash mostly disappears on its own within 3-5 days, accompanied by chaff-like flaking.
(7) Occasional recurrence with re-treatment. No complications or sequelae were observed. Histochemical examination revealed no difference in antimony content between the rash and normal skin (both about 2 or 5 μg/dl). Histopathology resembled contact dermatitis and was nonspecific.
3, papillary hyperplasia type: mostly caused by the long-term use of levo-iodine, bromides, etc.. The incubation period is often large about one month. We have seen 2 cases, on the basis of the whole body erythematous drug rash appeared scattered distribution, not very regular, significantly higher than the skin surface, about 3-4cm, diameter of myxoid papillary proliferative granuloma, touch is quite solid, mainly in the trunk. The granuloma gradually subsides after symptomatic treatment and lasts for about 3 weeks.
4. Lupus-like reactions: Since the discovery of hydrazidiazine in the early 1960s, more than 50 kinds of drugs such as penicillin, procainamide, isoniazid, para-aminosalicylic acid, pautazone, methylsulfoximine, rifampin, methotrexate and oral contraceptive drugs are known to cause such reactions. The main clinical manifestations are polyarthralgia, myalgia, polypoiditis, pulmonary symptoms, fever, enlargement of the liver, spleen and lymph nodes, cyanosis of the extremities and skin rash. The syndrome differs from true lupus erythematosus in that fever, tubuluria, hematuria and azathioprine cause it, and positive laboratory tests can persist for months to years after the symptoms disappear.
5. Fungal disease-type reactions: Due to the application of a large number of antibiotics, corticosteroids and immunosuppressive agents, they often cause disturbance of the environmental balance and dysbiosis in the body and fungal case reactions, manifesting as Candida albicans, Aspergillus or dermatophyte infections, the first two of which may have gastrointestinal, pulmonary or other visceral infections and may involve multiple organs at the same time. It is not uncommon for severe systemic fungal infections to be found in the autopsies of people who were on immunosuppressive drugs during their lifetime. It is worth noting that in some cases of dermatophytosis, ringworm lesions become more widespread and less treatable due to the application of the above mentioned drugs, and even if cured, they are prone to relapse, causing difficulties in the prevention and treatment of ringworm.
6. Corticosteroid-type reactions: If hormones are applied in larger doses and for longer periods of time, they can often cause a variety of adverse reactions and even incur death. The main side effects caused by it are.
(1) Secondary bacterial or fungal infection: the most common.
(2) Gastrointestinal tract: “steroid ulcers”, even complicated by bleeding and perforation.
(3) Central nervous system: euphoria, agitation, dizziness, headache, insomnia, etc.
(4) Cardiovascular system: palpitations, elevated blood pressure, thrombosis, cardiac arrhythmia, etc.
(5) Endocrine system: Cushing’s syndrome, osteoporosis, glycosuria, hypocorticism and growth inhibition in children.
(6) Skin: acne, hirsutism, capillary dilation, petechiae, skin atrophy, etc.
(7) Eye: blurred vision, increased intraocular pressure, cataract and glaucoma, etc.