Formulating a diagnosis
Components of the diagnosis: - prevalence of lesions;
- morphological signs;
- severity
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Cutaneous adverse drug reactions (CADR), also known as toxidermia (syn.: toxicoderma, toxic-allergic dermatitis), are skin manifestations resulting from systemic drug administration.
These reactions range from mild erythematous skin lesions to much more severe reactions such as Lyell’s syndrome. They represent a heterogeneous field, including various clinical patterns without specific features suggesting drug causality.
The term “toxidermy” was suggested by German dermatologist Jadassohn who studied allergy problems in the 1890s and 1900s.
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Most systemic drugs (such as antibiotics, anticonvulsants, antineoplastic drugs, nonsteroidal anti-inflammatory drugs, and allopurinol) are potential causes of cutaneous adverse reactions.
There are multiple mechanisms that account for the variability in drug reactions. They can be classified into two general categories: immunologic and nonimmunologic. Most adverse drug reactions are secondary to predictable, non-immunologic effects, while the residual (adverse reactions are caused by unpredictable effects, some of which may be immune-mediated. Only 5–10% of all adverse drug reactions are immune-mediated.
Prevalence of lesions
- Generalized.
- Localized.
- Single element.
Morphological features
Characteristics of skin rash morphological elements in drug-induced toxidermia are displayed in table 9.1 below.
Table 9.1. Morphological elements of skin rash in drug-induced toxidermia
| Morphological elements of skin rash | Characteristics of elements |
| Macula (spot) | Erythematous, pigmented or hemorrhagic spots may appear.
Localization — the skin of the trunk, face, limbs, palms and soles, large folds. Macula surface is smooth, in the future, defurfliration, xanthopathy, follicular keratosis is possible, in consequence of which maculae acquire a more saturated color. Maculae appear after taking medications or gradually (within 2–3 days) with subsequent disappearance |
| Papula (nodule) | Papules of bright red color, up to several millimeters in diameter, are located symmetrically on the skin of the trunk and limbs, are prone to fusion |
| Nodus (node) | Dense elastic nodes, painful on palpation, localized on the shins and thighs, sometimes on the face. The skin on nodes is bright red, after a few days, it becomes cyanotic. Evolution of the nodes takes about a month, followed by peeling and hyperpigmentation |
| Vesicula (bubble) | Palms and soles are more often affected, but rashes may occupy more larger skin areas, accompanied by voluminous oozing lesions and subsequent macrolaminar desquamation |
| Bulla (blister) | Large blisters with localization mainly in the skin folds. After rupture, vegetative erosions are formed |
| Pustula (pustule) | Localization in areas with sebaceous glands: face, chest, interscapular area. They develop in the first two weeks of taking medications. Large, grouped purulent acne-like elements that have a tendency to merge into plaques with large scallop edges may acutely appear. Plaques and tumor-like infiltrates are covered with bloody-purulent crusts, when they are removed, ulceration foci with papillomatous masses are discovered. The lesions are painful, bleed easily, are multiple, with purulent voluminous discharge from many sites. New lesions may occur for a long time after drug discontinuation |
| Urticaria (weal) | Weals have no typical localization, itching and burning are subjectively possible. There is a tendency to merge in places of greatest friction (buttocks, lumbar region, shoulders, hips). On the face, weals practically do not protrude above the skin level. Initially, weals have a pink color, then, as the swelling and compression of small vessels increases, they acquire a porcelain-white color. With reduction of edema, the color gradually changes to pink, and subsequently the weals disappear without a trace. Combination with Quin’ke’s edema is possible, as well as bronchospasm, dyspepsia, arthralgia |
In case of toxidermia, rashes can be monomorphic or polymorphic (maculopapular, maculovesicular, vesicular-bullous).
Severity
Assessment of toxidermia severity is carried out on the basis of lesion prevalence and nature on the skin and mucous membranes, physical examination data, patient complaints and laboratory data (table 9.2).
Table 9.2. Toxidermia severity and its characteristics
| Degree of severity | Characteristic |
| Mild | Skin damage of up to 10% of the surface in the absence of cavities and hemorrhagic elements. No damage to mucous membranes is observed. A slight change in laboratory parameters with patient’s satisfactory condition |
| Moderate | A common skin lesion, absence of bullous and hemorrhagic elements. Intense skin itching. Eosinophilia, moderate increase in ESR |
| Severe | Subtotal or total lesion of the skin and mucous membranes, bullous
and/or hemorrhagic rash elements, soreness on palpation of the affected and unaffected skin areas, systemic signs and symptoms, fever, significant deviations in laboratory parameters |