Background Deficiency of Alpha-1 Antitrypsin (D-AAT) is one of the most common serious hereditary diseases worldwide, however, remains an under diagnosed entity.

Objectives To characterise children with D-AAT followed in a level 2 hospital (2000–2013).

Methods Retrospective analysis of clinical records of children with D-AAT followed in a paediatrics digestive pathology consultation.

Results 41 cases (61%males) were diagnosed. The average age at diagnosis was 6 yrs (1 month^-15 yrs).

The diagnosis was established in the following settings: study of allergies in26.83%; family history in 21.95%; lower respiratory infections in 9.76%;asymptomatic elevation of transaminase in 7.32%; Escreva texto ou o endereço de um Web site ou traduza um documentoTraduzirdo: Portuguêsneonatalcholestasis, prolonged neonatal jaundice, and persistent transaminase elevations after acute gastroenteritis in 4.88% each; others pathologies in 34.14%.

Immunophenotyping allowed detection of alleles Z and S, in 85% and 40%, respectively. Other pathological alleles identified less frequently were the I, V and Mmaltom. The phenotype identified were: MZ in 32.5%, SZ 26.8%, ZZ 19.5%, SS and IZ4.88% each; MS, MV, SV, and SM maltom 2.5% each.

In 100% of cases the presence of at least one disease in parental allele was verified.

Discussion The most common pathological allele was the Z, and the predominant phenotype was MZ. All children are clinically well, without complications. We highlight the need for awareness of the scientific community for the early diagnosis of this entity in order to implement interventions to prevent the progression of lung disease by decreasing any proinflammatory stimuli, and to undertake family studies to ensure early diagnosis of other cases and provide genetic advice.