[Translated article] Haptens, Proteins, and Atopic Dermatitis

Atopic dermatitis is a chronic inflammatory disease that is multifactorial in nature. Allergic contact dermatitis and protein contact dermatitis are allergic conditions that may occur in the context of atopic dermatitis and be the cause of exacerbations. Although the prevalence of allergic contact dermatitis is similar in atopic patients and the general population, these 2 conditions are frequently associated because atopic inflammation disrupts the skin barrier. Skin tests are therefore recommended in atopic individuals. Dupilumab could be useful for treating allergic contact dermatitis if it is mediated by type 2 helper T cells but could exacerbate inflammation if mediated by T_H1 cells: further study is needed before conclusions can be drawn. Although the mechanism by which exposure to environmental proteins exacerbates atopic dermatitis remains under discussion, such exacerbations are routinely seen in clinical practice. Prick testing is recommended in symptomatic atopic dermatitis. When prick-test findings are positive, patients should be advised to avoid the culprit substances.

Haptens, Proteins, and Atopic Dermatitis

Atopic dermatitis is a chronic inflammatory disease that is multifactorial in nature. Allergic contact dermatitis and protein contact dermatitis are allergic conditions that may occur in the context of atopic dermatitis and be the cause of exacerbations. Although the prevalence of allergic contact dermatitis is similar in atopic patients and the general population, these 2 conditions are frequently associated because atopic inflammation disrupts the skin barrier. Skin tests are therefore recommended in atopic individuals. Dupilumab could be useful for treating allergic contact dermatitis if it is mediated by type 2 helper T cells but could exacerbate inflammation if mediated by T_H1 cells: further study is needed before conclusions can be drawn. Although the mechanism by which exposure to environmental proteins exacerbates atopic dermatitis remains under discussion, such exacerbations are routinely seen in clinical practice. Prick testing is recommended in symptomatic atopic dermatitis. When prick-test findings are positive, patients should be advised to avoid the culprit substances.

Insulin allergy: a diagnostic and therapeutic strategy based on a retrospective cohort and a case-control study

AIMS/HYPOTHESIS

Insulin allergy is a rare but significant clinical challenge. We aimed to develop a management workflow by (1) validating clinical criteria to guide diagnosis, based on a retrospective cohort, and (2) assessing the diagnostic performance of confirmatory tests, based on a case-control study.

METHODS

In the retrospective cohort, patients with suspected insulin allergy were classified into three likelihood categories according to the presence of all (likely insulin allergy; 26/52, 50%), some (possible insulin allergy; 9/52, 17%) or none (unlikely insulin allergy; 17/52, 33%) of four clinical criteria: (1) recurrent local or systemic immediate or delayed hypersensitivity reactions; (2) reactions elicited by each injection; (3) reactions centred on the injection sites; and (4) reactions observed by the investigator (i.e. in response to an insulin challenge test). All underwent intradermal reaction (IDR) tests. A subsequent case-control study assessed the diagnostic performance of IDR, skin prick and serum anti-insulin IgE tests in ten clinically diagnosed insulin allergy patients, 24 insulin-treated non-allergic patients and 21 insulin-naive patients.

RESULTS

In the retrospective cohort, an IDR test validated the clinical diagnosis in 24/26 (92%), 3/9 (33%) and 0/14 (0%) likely, possible and unlikely insulin allergy patients, respectively. In the case-control study, an IDR test was 80% sensitive and 100% specific and identified the index insulin(s). The skin prick and IgE tests had a marginal diagnostic value. Patients with IDR-confirmed insulin allergy were treated using a stepwise strategy.

CONCLUSIONS/INTERPRETATION

Subject to validation, clinical likelihood criteria can effectively guide diabetologists towards an insulin allergy diagnosis before undertaking allergology tests. An IDR test shows the best diagnostic performance. A progressive management strategy can subsequently be implemented. Continuous subcutaneous insulin infusion is ultimately required in most patients.

CLINICALTRIALS

gov: NCT01407640.

Allergic Maculo-Papular Exanthema Due To Terbinafine

We report on a 76-year-old male patient who developed a maculopapular generalised exanthema due to terbinafine. Prick test was negative; patch test revealed a positive reaction after 48 h confirming the delayed-type allergic reaction. Non-pustular exanthema has only rarely been reported for terbinafine.

Dermatophagoides pteronyssinus: Changes in sensitisation in the past 11 years and comparison with other centres in Mexico

BACKGROUND

House dust mites are a ubiquitous air allergen in the human habitat. It has been shown that exposure to them is a fundamental factor in sensitisation and development of atopic disease. The objective of the study was to analyse changes in sensitisation to Dermatophagoides pteronyssinus (Der p.) in children treated in a tertiary level care hospital in Mexico City for a period of 11 years and compare with other studies carried out in Mexico.

METHODS

A retrospective study was performed at the Hospital Infantil de México Federico Gómez (HIMFG). Information was gathered from skin tests for Der p. performed in the Allergy Laboratory from January 2004 to April 2015. Patients 2-18 years old who presented for examination of some type of allergic condition and who had immediate hypersensitivity tests to Der p. were included in the study. Results were compared with prior reports from other institutions. Descriptive analysis and χ² statistics were used.

RESULTS

A total of 8794 patients were included in the study; 49.3% of the tests (95% CI 48-50) were positive for Der p. The percentage of monosensitised to mites was 2.7% for Der p. (95% CI 2-3). A significant difference was found between the results of older patients and those <6 years old. The frequency of sensitisation had a tendency to decrease during the 11 years analysed in all age groups.

CONCLUSIONS AND CLINICAL RELEVANCE

The frequency of sensitisation to Der p. increased with age until reaching adolescence. In the last 11 years a decrease in sensitisation to this air allergen was observed.

[Type I hypersensitivity to nocturnal Lepidoptera in a Costa Rican allergic population]

BACKGROUND

Allergic patients are routinely tested for various allergens including molds, food, pollen, cockroaches and house dust mites; however, there are patients who present allergy symptoms but show negative results in Prick tests with the available allergens.

OBJECTIVE

To determine the percentage of patients sensitized to the nocturnal Lepidoptera and its role as an important environmental allergen.

MATERIAL AND METHOD

A retrospective analysis was carried out in which we determined the percentage of patients allergic to nocturnal Lepidoptera, house dust mites (Blomia tropicalis, Dermatophagoides pteronyssinus, Dermatophagoides farinae and Tyrophagus putrescentiae) and insects (Periplaneta americana and Musca domestica). Also, we analyzed the demographics and symptoms of the patients.

RESULTS

63% of the patients were allergic to house dust mites, 39% to nocturnal Lepidoptera, 28% to Periplaneta americana and 24% to Musca domestica. Also, 2% of the patients allergic to only one allergen were mono-sensitized to nocturnal Lepidoptera.

CONCLUSIONS

We strongly recommend that allergists constantly test for nocturnal Lepidoptera, because most of the studied patients had allergy to these insects.

Risk of adverse IgE-mediate reaction at the first egg ingestion in children with atopic dermatitis. Results of a case-control study

BACKGROUND

Studies have reported that children with atopic dermatitis (AD) have a high risk of adverse reactions at first egg ingestion.

METHODS

We enrolled 79 children with AD retrospectively and 45 children without AD (control group) prospectively, who had never eaten egg. All children underwent skin prick tests (SPT) with commercial extracts and prick by prick with natural food (raw and boiled egg). Oral food challenge (OFC) was performed in SPT positive patients.

RESULTS

Sixty-six percent (52/79) of AD group and 11% (5/45) of Control group had at least one positive SPT (p<0.001), Relative Risk (RR)=5.9 and Odds Ratio=15.4. Of the 46/52 sensitised children in the AD group, 36 children ate egg for the first time in hospital during an OFC and 10 children ate egg at home because of their parents' choice, with 19/46 (41%) resulting in allergic reactions to raw and/or boiled egg. Four/five sensitised children in the control group underwent OFC and three of them (75%) showed an allergic reaction to raw, but not boiled egg. Thirty percent (14/46) of AD group had a systemic reaction vs. 25% (1/4) of Control group.

CONCLUSION

A child with AD has a RR of sensitisation to egg six times higher than a child without AD, before the first known ingestion. We propose to test sensitisation to egg in every child with AD who has never eaten egg, and to perform OFC in those with positive SPT in hospital setting.