Research Title: Evaluation of airway reactivity, allergy and inflammatory mediators in exhaled breath condensate in vitamin D resistant rickets.

Aim: To assess the effect of absence of vitamin D receptors on airway reactivity, allergy and inflammatory mediators in exhaled breath condensate in a prospective study evaluating patients with vitamin D resistant rickets and in healthy controls.

Sample size: 40 participants in the two groups. Primary end point: Airway reactivity as assessed by methacholine challenge test.

Secondary outcome parameters: All other parameters are the secondary end points.

Research Title: Evaluation of airway reactivity, allergy and inflammatory mediators in exhaled breath condensate in vitamin D resistant rickets.

Introduction: Vitamin D seems to play a role in allergic and asthmatic reactions. Vitamin D resistant rickets patients lack vitamin D receptors and cannot absorb vitamin D.

Aim: To assess the effect of absence of vitamin D receptors on airway reactivity, allergy and inflammatory mediators in exhaled breath condensate.

Design: Prospective study evaluating these parameters in patients with vitamin D resistant rickets and in healthy controls.

Participant selection: The study group will consist of vitamin D resistant rickets patients followed and treated at the Pediatric Endocrinology Department at our hospital. The study group will be compared to an age- and sex-matched healthy control group that had a negative methacholine challenge test.

Sample size: 40 participants in the two groups. Intervention: Each subject will undergo evaluation including a respiratory questionnaire, pulmonary function tests, methacholine challenge test with determination of PC20, exhaled nitric oxide (eNO), and exhaled breath condensate (EBC). Venous blood will be analyzed for complete blood count + eosinophils, IGE levels, and Vitamin D levels. Prick skin test for inhaled allergens will be performed. All measurements will be evaluated in a single 3 hour visit, with no follow up study visits.

Primary end point: Airway reactivity as assessed by methacholine challenge test.

Secondary outcome parameters: All other parameters are the secondary end points.

Inclusion Criteria:

• Vitamin D Resistent Rickets
• Age between 3 - 40 years

Exclusion Criteria:

• Any Chronic Lung Disease
• Febrile Illness in last 2 weeks
• Inhaled Corticosteroids over the past 2 weeks
• Bronchodilators over the past 24 hours
• Participation in any other clinical studies over the past 4 weeks