Lentil hypersensitivity pneumonitis as a masquerader in an infant with recurrent pneumonia

INTRODUCTION

Infants presenting with atypical pneumonia are common. While infective etiology is often investigated, hypersensitivity pneumonitis (HP) is seldom evaluated.^[1,2] The key to early detection is early suspicion of hypersensitivity. Here, we describe an infant with recurrent pneumonia who, despite initial management,^[3] had persisting symptoms, prompting further evaluation for hypersensitivity. While less common than allergies to peanuts or soy, lentil hypersensitivity is becoming increasingly recognized, particularly in certain regions.^[4] HP due to lentils is a specific type of lung inflammation caused by inhaling/aspiration of lentil dust or particles. While less common than other forms of lentil allergies, it is important to understand its unique characteristics and potential risks.

CASE REPORT

This one-year-old, firstborn of non-consanguineous marriage, developmentally normal infant presented with a history of recurrent episodes of bronchitis and conjunctivitis during the spring period, failure to thrive with height and weight <3 standard deviation (SD). Antenatal and birth history were unremarkable. There was no history of contact with tuberculosis (TB), recurrent diarrhea, oily stool, recurrent ear discharge, food allergy, or exposure to pigeons. There was no history of indoor pollution and smoking in the family or any early sibling deaths. The child started on weaning foods, including wheat, rice, and lentils, at 6–8 months with a history of vomiting post-feed frequently and forced feeding. The infant had repeated hospital visits for the same and was managed conservatively. Despite repeated medications (antibiotics and anti-gastroesophageal reflex [GER] measures), the infant had transient asymptomatic phases. He had failure to thrive despite these measures and persistent forceful feeding habits.

On arrival at this tertiary care hospital with features of pneumonia (tachypnea and cough), the baby was thoroughly investigated with initial differentials of primary immunodeficiency, protracted bacterial bronchitis, and GER disease and started along with a short course of antibiotics for a two-week duration. The investigations are attached as per Table 1. The radionucleotide milk scan was positive for GER grade 2 [Figure 1]. Chest X-ray was suggestive of bilateral perihilar opacities indicating recurrent micro aspirations [Figure 2], and contrast-enhanced computed tomography chest showed peri bronchial consolidation predominantly involving the upper and middle lobes. Bronchoalveolar lavage (BAL) revealed predominant lymphocytes with eosinophils, and BAL GeneXpert for TB was negative. In view of the characteristic features of HP, further workup considering lentil hypersensitivity was done which was serum immunoglobulin E (IgE). Lentil Ag was raised by 22.1 kilounits/litre (kUA/L); normal range <0.1 kUA/lt. Prick tests confirmed an allergy to lentils but were negative for other common food allergens.

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Figure 1:

Gastroesophageal reflux scan; high reflux noted.

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Figure 2:

Chest X-ray posteroanterior view showing peribronchial opacities suggestive of microaspirations.

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DISCUSSION

Hypersensitive pneumonitis is one of the leading interstitial lung diseases in children, with a prevalence of 4 in 1 million.^[5] The common manifestations of HP are non-specific and include cough, fever, tachypnea, or respiratory distress. At present, there are no diagnostic criteria for HP in the pediatric population and respiratory symptoms; the high-resolution computed tomography findings are helpful in establishing the diagnosis.^[5] BAL and lung biopsy have added diagnostic values but may not always be necessary when the history of exposure and typical radiological findings are conspicuous. Lentils are grown in many temperate and subtropical regions worldwide. While they are commonly eaten, there is limited information in literature about severe allergic reactions, like anaphylaxis, caused by consuming them.^[4] The growing number of reported lentil allergies has led to research into how lentils might cause allergic reactions. Two types of allergens have been identified in boiled lentils. These allergens are proteins L1, L2 (both 16 kDa), and L3 (12 kDa), which are related based on their structure and immune properties. Protein L1 was found to be a significant allergen in lentil allergy. This was supported by its high recognition rate (68%) by patient sera and its ability to inhibit (64%) IgE binding to commercial lentil allergen extracts.^[6] The second allergen identified in boiled lentils is protein H, a 66 kDa component that binds to IgE. Purified protein H was recognized by 41% of patient sera and inhibited IgE binding to commercial lentil extracts by 45%. Boiling lentils appears to break down existing allergens into smaller fragments, which may have stronger allergenic properties.^[7] The most likely explanation for these allergic reactions is IgE-mediated hypersensitivity. This occurs when a person’s immune system becomes sensitized to a food after eating it and then reacts to it through an IgE-mediated response.^[8]

As a result, the person may experience symptoms even after simply inhaling the vapors from boiling food, similar to what happens in inhalant allergies, with clinical manifestations involving various organs such as the lungs and skin, and even evolving in anaphylaxis. In our index case, the hypersensitivity might be primarily due to increased aspirations due to GER. Unlike previous cases, our patient experienced very early symptoms, starting before the age of one. There are no reported cases of anaphylaxis in children so young, especially when they are already on a lentil-free diet.

Our case highlights that a strict diet may not always prevent allergic reactions, and these reactions can occur even after inhaling cooking vapors. Although rare, this risk should be considered in children who have a food allergy, even if they follow an exclusion diet.

CONCLUSION

HP is an immune-mediated inflammatory reaction that affects the lungs. HP due to lentils is a specific type of lung inflammation caused by inhaling lentil dust or particles. It is distinct from the more common food allergy to lentils, where the reaction occurs through ingestion.

• Inhaling lentil dust or particles triggers an abnormal immune response, leading to inflammation and damage to the lung tissue.

• This can cause a range of symptoms, from mild cough and shortness of breath to severe respiratory distress.

Early identification and dietary management, combined with targeted interventions like steroids in severe cases, can lead to significant improvement in patient outcomes and prevent the progression of disease to chronic lung disease. The key to early diagnosis lies in early suspicion of hypersensitivity, especially in weaning infants who are force-fed and/or neurologically compromised. This case highlights the potential for severe reactions to lentils, even in previously unexposed individuals. Early recognition and intervention are crucial in anaphylaxis management. Parents and healthcare professionals must be aware of this emerging allergy and have a low threshold for suspicion.