Lipid transfer protein allergyT78.1

Food allergy to lipid transfer prote ins (LTP). Lipid transfer proteins (LTP) are considered important plant allergens in the Mediterranean region. They are frequent triggers of urticaria, anaphylaxis and oral allergy syndrome (OAS). LTPs are the most common causes of FDEIA in the Mediterranean region, with peach and apple being the most common allergens (Wolters P et al. 2022)

The first symptoms of an LTP food allergy usually appear before the age of 12. M:w=1:1. In larger studies with suspected food allergies, around 6-10% are found to have LTP food allergies. The age at onset of the first symptoms is preferably between 12 and 17 years. The median time to diagnosis after the first onset is about 4 years.

With a prevalence of approx. 6-10%, food allergies are one of the most important immediate-type allergies in Europe. There is considerable variability in the triggering allergens in the different European regions (Lyons SA et al. 2019). Lipid transfer proteins (LTP) are ubiquitous proteins that are highly conserved. They are found in numerous plant foods, including pollen. LTPs are the most relevant allergens of rosaceae fruits in the Mediterranean region. They are widespread in the plant kingdom and have a moderately to highly homologous molecular structure.

Since anaphylaxis can be associated with LTP allergy and co-factors increase the severity of the reaction, it is of fundamental importance to recognize LTP allergy already in children. Currently available diagnostic tests (SPT and sIgE) cannot accurately predict this form of food intolerance. Nor are they able to assess the severity of the reaction.

LTPs can also occur in a number of botanically unrelated foods, including fruits, nuts, seeds, vegetables and grains, and thus become allergologically relevant (Rona RJ et al. 2007). As LTPs can cause severe systemic reactions, it is important to detect this particular form of allergy at an early stage, i.e. as early as childhood. A larger study showed that fresh fruit is the fifth most common cause of anaphylaxis in children, followed by nuts, both of which are possibly caused by LTPs in Central Europe (Gaspar A et al. 2021).

>60% of LTP food allergy sufferers have an atopic constitution.

>50 % show pollen sensitization, 50-60 % rhinitis, 30 % asthma, 20 % atopic dermatitis. Eosinophilic esophagitis is rarely detectable.

70% of patients show reactions to >1 food. Fruit is reported as an allergen in around 70%, nuts in 50%, peanuts in 8% and sesame in 4%. Occasionally, other allergies (cow's milk allergy) are also detected.

Peach is the most common trigger (around 60%).

30% of LTP food allergy sufferers show symptoms with both fruit and nuts.

60% of patients have only systemic symptoms, about 15% have only local symptoms and 27% have both systemic and local symptoms.

In contrast to patients with a birch pollen-associated food allergy (symptoms appear 10-15 minutes after allergen contact), the clinical symptoms in LTP allergy sufferers only develop after 15-60 minutes.

The clinical symptoms are distributed as follows: Urticaria (60%), anaphylaxis (40-50%) OAS (40%). Patients who were exclusively allergic to fruit are 70% female, the median age at onset of symptoms is (1-6) years. About 50% of LTP allergic patients report severe grade 3 anaphylaxis, about 90% report contact urticaria when peeling potatoes or cucumbers or kneading bread dough containing wheat.

Patients who are exclusively allergic to nuts/peanuts/seeds are 60% male, and anaphylaxis is to be expected in 53%. Co-factors are to be expected in around 30% of patients.

Medical history with assessment of immediate allergic reactions to plant foods (i.e. repeated symptoms to LTP-containing foods on multiple occasions).

Positive skin prick test (positivity is defined as the "mean diameter of the wheal ≥ 3 mm compared to the negative control) to LTP extract.

Positive specific IgE (sIgE) against LTP allergens (Pru p 3, Cor a 8 and/or Jug r 3).

Detection of co-factors (physical activity and NSAIDs in connection with allergic symptoms).

Determination of food tolerance (food tolerance is defined as non-reactivity to foods in the usual diet).

Prophylaxis: Food avoidance is the mainstay of treatment for LTP allergy and should be based on clinical reactivity rather than sensitization (Asero R et al. 2018). Intake of tolerized foods can be continued without a bowl, attention should be paid to the presence of co-factors. This approach can be used to maintain a natural tolerance and intake of important nutritious foods such as fruits and vegetables. Fruits from the Rosaceae family are mostly tolerated without the peel, as LTP are mainly found in the fruit peel (Niggemann B et al. 2014; Rossi RE et al. 2009).

Awareness of possible incidental allergic reactions and the ability to correctly recognize and appropriately treat them is of utmost importance in LTP-sensitized individuals. Children and their caregivers should be fully educated about potential triggers, timely recognition of reactions, appropriate treatment and the role of co-factors in LTP allergies.

Further advice: All individuals with systemic reactions to LTP-containing foods with or without co-factors should have adrenaline autoinjectors readily available. This measure is not absolutely necessary for persons in whom only local reactions are to be expected. A not insignificant percentage of patients (about 10%) have reported reactions to new LTP-containing foods, although the timing of the initial reaction may vary. It should be noted that the LTP allergy can spread to other triggering foods.

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