Rarity of hypertension in adult patients with atopic dermatitis

BACKGROUND

Patients with atopic dermatitis show a tendency for vasoconstriction of the small vessels in the skin. As peripheral vasoconstriction contributes to the cause of hypertension, it is natural to suppose that blood pressures might be on the high side in adult patients with atopic dermatitis. In the literature, however, there was little information on the subject.

OBJECTIVES

To study the incidence of hypertension in adult patients with atopic dermatitis.

PATIENTS/METHODS

Blood pressure was measured in 521 adult patients with active atopic dermatitis (235 males; 286 females) aged 30-59 years, and 87 adults with "healed" atopic dermatitis (26 males; 61 females) aged 34-52 years. The blood pressures were classified as definite hypertension, borderline hypertension or normal blood pressure.

RESULTS

In those patients aged 30-39 years with active atopic dermatitis, the incidence of definite hypertension in the male patients and the female patients was 1.1% and 1.6%, respectively. The incidence remained almost at a plateau for the 30-39-year-old age group through to the 50-59-year-old age group, in both the male and female patients. There was no difference in the incidence of definite hypertension between patients with severe dermatitis and patients with mild dermatitis. Adult patients with "healed" atopic dermatitis also showed a low incidence of definite hypertension.

CONCLUSIONS

These findings indicate that hypertension is rare in adult patients with atopic dermatitis. It is most probable that the rarity of hypertension is a primary feature of the disease.

Irritant susceptibility and weal and flare reactions to bioactive agents in atopic dermatitis. I. Influence of disease severity

The two main pathogenetic characteristics of atopic dermatitis (AD) are: (i) antigen-dependent 'specific' reactivity, and (ii) altered non-immunological 'non-specific' reactivity. Our understanding of the role of non-specific reactivity is hampered by the fact that methods available for its quantification are limited. The aim of the present study was to assess the usefulness of two parameters as quantitative measures of non-specific skin reactivity in AD: (i) susceptibility to repeated epicutaneous exposure to an irritant (sodium lauryl sulphate, SLS), assessed by visual scoring and transepidermal water loss (TEWL) measurement, and (ii) reactivity to intracutaneously injected bioactive agents (codeine, FMLP, histamine, methacholine, substance P, trypsin), assessed by measurement of weal and flare size. These two parameters were tested in a group of AD patients, subdivided according to the severity of their dermatitis, and a control group. The visual score and TEWL after SLS exposure tended to be higher in the AD group than in the control group. Furthermore, visual score and post-exposure TEWL were positively correlated with the dermatitis severity score. Weal size following injection of codeine, histamine and substance P, and flare size following injection of all agents, except methacholine, were significantly lower in the AD group than in the control group. Negative correlations were found between weal and flare sizes and the dermatitis severity score. These findings can be explained by down-regulation of structures involved in weal and flare reactions. In conclusion, we propose that epicutaneous irritant susceptibility and reactivity to intracutaneous bioactive agents may be useful indicators of non-specific skin reactivity in AD.

Phosphodiesterase and immune dysfunction in atopic dermatitis

Atopic dermatitis and the other atopic conditions occur as a result of direct or indirect influences from cells of hematopoietic origin. Cellular immune abnormalities have been described, but appear to be secondary to cutaneous inflammation in atopic dermatitis. Pharmacophysiologic abnormalities are numerous and may relate to defective cyclic nucleotide metabolism in circulating and infiltrating leukocytes. A consistent leukocyte abnormality is elevated cyclic AMP-phosphodiesterase. This enzyme abnormality results in reduced intracellular cyclic AMP, creating a net permissive effect upon cell function. Phosphodiesterase inhibitors have been demonstrated to reduce abnormal histamine release and IgE production by cultured leukocytes. Studies of phosphodiesterase and associated defects in atopic leukocytes may lead to delineation of basic pathogenetic mechanisms as well as providing the potential for therapeutic targeting.

Plasminogen activators and antiplasmin activity in atopic dermatitis

Cutaneous deposits of fibrinogen activity in lesional skin, plasmatic fibrinolytic activity, and antiplasmin activity (alpha 2 macroglobulin, alpha 1 antitrypsin and antithrombin III) were evaluated in a group of ten patients with atopic dermatitis and in a sex- and age-matched control group. Plasma fibrinolytic activity was increased in the acute phase of the disease (p less than 0.05). The levels of circulating antiplasmins appeared similar in the patients and the control group. Cutaneous fibrinolytic activity was increased in the acute phase of the disease in 5 of 5 cases, suggesting a role of the fibrinolytic system in the amplification of the inflammatory phenomenon in that phase of the disease. In the chronic lichenified phase, CFA was decreased in 3 of 5 cases leading to an excessive deposit of fibrin in the skin. This could be correlated with the abnormal vascular response (blanching phenomenon). On the basis of these data, the therapeutic use of the antifibrinolytic agents only seems rational in the acute phase of the disease.

Inability to produce white dermographism in the early stage of infantile eczema

White dermographism constitutes an abnormal vascular reaction characteristically demonstrable in atopic dermatitis; however, there is no information about it in the infantile phase of atopic dermatitis. Therefore we examined 73 infants younger than 3 years of age with eczematous dermatitis for the demonstrability of white dermographism after mechanical stroking of the lesional skin. None of the 40 healthy control infants showed white dermographism on their normal skin. In contrast, an age-dependent increase was demonstrated in patients with infantile eczema, from 11% in those 1 to 2 months of age to 85% in those older than 7 months. There was no correlation between the demonstrability of white dermographism in early infancy and the prognosis of infantile eczema. Based on our study of various types of dermatitis experimentally induced in adult volunteers, we think that, in addition to the immaturity of infantile skin, the presence of acute dermatitic changes may be related to inability to demonstrate white dermographism in the early phase of infantile eczema.

The cellular inflammatory response in nicotinate skin reactions

Sequential skin biopsies of nicotinate-treated skin from nine normal subjects, three aspirin-pretreated normal subjects and six atopic eczema patients were examined. An erythematous skin reaction was seen in the nine normal subjects and to a lesser degree in one atopic eczema patient, but not in the aspirin-pretreated subjects nor in five remaining atopics. Accumulation of a mononuclear cell perivascular infiltrate was seen from 15 min onwards in the normal subjects. Neutrophils became the predominant cell invading thickened vessel walls and in the perivascular space beginning at 2 h and persisting up to 48 h. Leucocytoclasis was observed at 24 h. Immunofluorescence studies showed only non-specific fibrinogen deposits in papillary capillaries in the three groups of subjects. The chloroacetate esterase reaction and immunohistochemical labelling with OKM I confirmed a marked neutrophilia at 2 h and 24 h. Neutrophils were seen in one atopic eczema patient, but were not observed in the remainder, nor in the skin of the aspirin-pretreated normal subjects. Topical application of nicotinate causes non-allergenic, leucocytoclastic vascular damage in normal skin which can be inhibited by aspirin and which is reduced or absent in atopic eczema.

Pharmacophysiology of atopic dermatitis

Atopic dermatitis is clearly characterized by altered cutaneous physiologic responses. There is a tendency to acral vasoconstriction. Rubbing causes skin pallor and white dermographism. Vascular instability is demonstrated by responses to cholinergic agents, histamine, and nicotinates. Psychophysiologic studies demonstrate exaggerated vasodilator responses to emotional stress with consequent pruritus and scratching. The itch threshold is low, duration is prolonged, and nighttime scratching movements may be frequent or almost continuous. Regardless of the inciting trigger factors, the scratching causes the damage and the severe dermatitis. Thermal as well as emotional stimuli to sweating cause severe itching in AD, yet the concept of a miliaria-type, poral occlusion mechanism remains unproven. Some studies suggest actually increased sweating along with erythema and pruritus during acute flares of AD. The concept of sweat-borne allergens causing skin reactions during sweating is interesting but has never been proven. Studies of sweat responses to pharmacologic agents have produced conflicting data, and attempts to link these responses to Szentivanyi's beta-adrenergic blockade theory are not convincing. The numerous variables of climate, season, sex, age, and habitus affect sweating greatly. Future studies must carefully control for each of these factors before pharmacologically induced sweat responses can be interpreted clearly. A number of lines of evidence suggest involvement of histamine and other mediators in the evolution of erythema, pruritus, and scratching in AD. Flares of the condition have been reproducibly evoked by only two incitants: experimental emotional stress interviews and specific food challenge in selected sensitive individuals. In the latter, increased plasma histamine has been demonstrated, presumably generated by antigen/IgE stimulated degranulation of mast cells in the gut and/or skin. The demonstrated increased histamine releasability of basophils from atopic individuals may be the result of defective cellular regulatory mechanisms. Recent studies have demonstrated increased cyclic AMP-phosphodiesterase activity in leukocytes from atopic individuals. The resultant decreased intracellular cyclic AMP removes an inhibitory factor, which in turn causes net cellular hyperresponsiveness. This effect has been shown to account, at least in part, for increased histamine release from leukocytes of patients with AD. These and other studies focused upon cell functional regulation are providing better understanding of basic biochemical abnormalities and may lead to improved diagnostic and therapeutic approaches in managing atopic disease.