Angiotensin converting enzyme (ACE) gene polymorphism in sarcoidosis in relation to associated autoimmune diseases

To investigate the significance of ACE gene insertion/deletion (I/D) polymorphism in the frequency of autoimmune manifestations in sarcoidosis.

In patients with sarcoidosis the ACE gene I/D polymorphism was detected with PCR on genomic DNA. The patients with sarcoidosis were divided according to the presence (n = 30) or absence (n = 32) of autoimmune manifestations. The former group was subdivided into thyroid autoimmunity (n = 10), gluten immune reactivity (n = 10) and gastric autoimmunity (n = 17).

The patients were recruited at the Department of Pulmonary Medicine, and the study was conducted at the Department of Endocrinology, University of Lund, Malmö University Hospital, Malmö, Sweden.

Sixty-two patients with documented sarcoidosis (30 females, 32 males, median age/range at diagnosis of sarcoidosis 31.5/19-75 years, median age/range at study 47.5/22-81 years) were examined. A total of 107 healthy unrelated subjects without sarcoidosis (60 females, 47 males, median age/range at study 58/40-82 years) served as controls.

S-ACE values were significantly increased in patients compared to controls (P = 0.00001). The same was true in the subgroup of sarcoidosis patients with associated autoimmunity compared with those with isolated sarcoidosis (P = 0.0328). A significant association was seen between ACE gene polymorphism (II, ID, DD genotypes) and S-ACE levels in both patients and controls according to the order II < ID < DD. The observed genotype frequency distributions in the different study groups agreed the Hardy-Weinberg equilibrium without significant differences between the patients and the controls. Within the group with autoimmune manifestations the DD genotype was significantly over-represented in X-ray stage III compared to the other X-ray stages (P = 0.0181) and a significant increase in the DD genotype in X-ray stage III (P = 0.035) in the group with autoimmune manifestations compared to isolated sarcoidosis was detected.

We confirmed that the S-ACE levels corresponded to the order II < ID < DD in patients with sarcoidosis as well as in healthy controls. S-ACE levels were significantly higher in sarcoidosis patients with autoimmune manifestations. The frequency of the DD genotype was significantly increased in patients with autoimmune manifestations and major granuloma mass (X-ray stage III). The ACE D allele in its homozygous form may confer susceptibility for autoimmune manifestations in sarcoidosis, possibly via the high levels of S-ACE it encodes.