Heterozygous α‐antichymotrypsin and PiZ (α1‐antitrypsin deficiency

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Abstract
In a case-control study we compared the prevalence of heterozygous deficiency of two closely related anti-neutrophil protease inhibitors, .alpha.1-antitrypsin and .alpha.1-antichymotrypsin, in 172 consecutive children with asthma. In a cohort study the clinical spectrum and severity were compared. On the basis of family studies 5/172 (2.9%) were classified as heterozygotes for .alpha.1-antichymotrypsin deficiency, a high prevalance compared with that of an unselected adult population (prevalence ratio 4.5 (1.7-11.9), P < 0.005). This finding suggests that the carrier state of this rare allele (prevalence 0.64%) may predispose to asthma in children. Among these heterozygous patients the prevalence of positive RAST tests for foodstuffs was significantly increased (prevalence ratio 4.8 (1.7-13.2), P < 0.005) and 2/5 manifested food allergy with Quincke oedema. Either the PiMZ or SZ phenotype of .alpha.1-antitrypsin deficiency was found in 12 (7.0%) of the 172 patients, a prevalence similar to that of a normal population (prevalence ratio 1.3 (0.67-2.6), P = 0.44). However, the asthma was more severe among the Z allele carriers, judged by the number of hospital admissions, compared with the non-Z asthmatic children (mean 2.92 vs. 1.72, P < 0.05). The results indicate that heterozygous deficiency of protease inhibitors directed against neutrophil proteases may affect the severity and clinical spectrum of childhood asthma, and to some degree be predisposing.