British Journal of Dermatology (1986) 115, 147-150. Elevated thymosin alpha i levels in Brazilian pemphigus foliaceus J.T.ROSCOE, P.H.NAYLOR*, L.A.DIAZ, R.S.LABIB, H.P.PATEL, A.L.GOLDSTEIN*, S.A.P.SAMPAIOf AND G.J.ANHALT Department of Dermatology, The Johns Hopkins Medical Institutions, Baltimore, MD, *Department of Biochemistry, The George Washington University School of Medicine, Washington, DC, U.S.A. and fDepartmento de Dermatologia, Faculdade de Medicina da Universidade de Sao Paulo, Sao Paulo, Brazil Accepted for publication i January 1986 SUMMARY Levels of thymosin alpha i in the sera of 37 patients with Brazilian pemphigus foliaceus (BPF) were measured using a competitive binding radioimmunoassay. The values were compared with 19 patients with other forms of pemphigus, 13 relatives of patients with BPF, 18 patients with other dermatological diseases, and 265 normal controls. We found that 27 (73%) of the patients with BPF had thymosin alpha i serum levels that were at least two standard deviations above the mean for normal individuals. The mean value for patients with BPF was significantly greater than any other groups studied. The thymosin elevation is similar to alterations seen in certain viral diseases and suggests that BPF is aetiopathogenically distinct from the other forms of pemphigus. Brazilian pemphigus foliaceus (BPF) is an autoimmune bullous disease that affects approxima- tely 10 000 individuals (Proenca & Castro, 1971). It is endemic to certain regions of South America, where cases occur almost exclusively in the rural population (Castro, Roscoe & Sampaio, 1983). This epidemiology suggests strongly that an infectious agent may be involved, possibly transmitted by an insect vector, but no aetiological agent has yet been demonstrated (Angulo, 1954). Beutner et al. (1968) were the first to demonstrate circulating autoantibodies to keratinocyte surface antigens in the sera of patients with BPF. Titres of these antibodies correlate with the severity of clinical disease. We have shown recently that purified IgG fractions prepared from the sera of patients with BPF are capable of inducing the characteristic epidermal lesions in neonatal Balb/c mice (Roscoe et al., 1984). These findings show that the autoantibodies are essential for induction of cutaneous lesions but the aetiology of the disease remains unclear. Thymic epithelium produces peptides that play a major role in the maturation of immunocompetent T cells. One of the best characterized is thymosin alpha i, which is known to increase the number of helper T cells and enhance resistance to bacterial, fungal and viral pathogens (Goldstein et al., 1983). Serum levels of thymosin alpha i are increased in viral Correspondence: Dr J.T.Roscoe, Department of Dermatology, The Johns Hopkins Medical Institutions, 600 N. Wolfe St., Baltimore, MD 21205, U.S.A. 147