Case Reports in Medicine Tests Throat culture Cold agglutination White blood cell Neutrophil Red blood cell Hemoglobin Platelets Erythrocyte sedimentation rate C-reactive protein ASO PPD Chest X-ray 3 Table 1: Laboratory data of the two cases. Case one Strep B hemolytic group A Negative 10100 72% 3.58 9.6 315000 75 2+ 400 Negative Normal Case two Strep B hemolytic group A Negative 7400 70% 4.22 11.4 334000 39 1+ 200 Negative Normal Normal value Negative lower than 1 : 32 4.3–10.8 × 103/mm3 45–74% 3.5–5 × 106/mcL 12.1–15.3 g/dL 150–450 × 103/mcL 30 mm/hr no CRP detectable less than 160 Todd units per milliliter Negative Normal Table 2: Retrospective studies that show variation according to geographical diﬀerences. Author Carlos et al. [6] Psychos et al.[3] Tay [7] Puavilai et al. [8] Year 2000 2000 2000 1995 Number of cases 106 patients (82 females) 110 females 75 patients (65 females) 100 patients (88 females) Country Spain Greece Singapore Thailand Idiopathic 35% 35% 60% 72% Infection 34% 17.3% 29% 18% Drugs are frequently implicated as the cause of erythema nodosum. Sulfonamides, bromides, and oral contraceptives have long been established as the most common medications contributing to EN. In those patients who develop erythema nodosum when an antibiotic is taken for an infectious disease it is diﬃcult to determine whether the cutaneous reaction is due to the antibiotic or due to the infectious agent [1, 11]. In publications and data bases, there is no report about simultaneous occurrence of erythema nodosum in monozygotic twins or in a family. Almost none of the studies reveal anything about genetics and heredity in the etiology of EN. Labunski et al. reported that patients with erythema nodosum associated with sarcoidosis produce an uncommon tumor necrosis factor (TNF-II). These patients show a nucleotide exchange, (G-A) at position 308 in the human TNF gene promoter, whereas patients with erythema nodosum without underlying sarcoidosis display a similar allele frequency compared with controls [12]. These results support the notion that erythema nodosum, in association with sarcoidosis, might be pathogenetically linked to altered TNF-α production due to a genetic promoter polymorphism [1, 3, 5]. In contrast, other authors have found that the proinﬂammatory cytokine pattern exhibits increased interleukin-6 serum concentrations both in infectious and noninfectious disease-related erythema nodosum, whereas a minor involvement of TNF is found in these patients [1, 11]. Our paper might help researchers elucidate the patho- genesis of EN. In addition, this paper might have diagnostic value in identifying patients with speciﬁc conditions associ- ated with EN. References [1] L. Requena and E. Sa´nchez, “Erythema nodosum,” Seminars in Cutaneous Medicine and Surgery, vol. 26, no. 2, pp. 114–125, 2007. [2] I. Volkov, I. Rudoy, U. Abu-Rabia, T. Masalha, and R. Masalha, “Case report: recurrent aphthous stomatitis responds to vitamin B12 treatment,” Canadian Family Physician, vol. 51, pp. 844–845, 2005. [3] D. N. Psychos, P. V. Voulgari, F. N. Skopouli, A. A. Drosos, and H. M. Moutsopoulos, “Erythema nodosum: the underlying conditions,” Clinical Rheumatology, vol. 19, no. 3, pp. 212–216, 2000. [4] A. Mert, R. Ozaras, F. Tabak, S. Pekmezci, C. Demirkesen, and R. Ozturk, “Erythema nodosum: an experience of 10 years,” Scandinavian Journal of Infectious Diseases, vol. 36, no. 6-7, pp. 424–427, 2004. [5] J. Whig, V. Mahajan, A. Kashyap, and S. Gupta, “Erythema nodosum: atypical presentation of common disease,” Lung India, vol. 27, no. 3, pp. 181–182, 2010. [6] C. Garcia-Porrua, M. A. Gonzalez-Gay, M. Vazquez-Caruncho et al., “Erythema nodosum, etiologic and predictive factors in a deﬁned population,” Arthritis & Rheumatism, vol. 43, no. 3, pp. 584–592, 2000. [7] Y. K. Tay, “Erythema nodosum in Singapore,” Clinical and Experimental Dermatology, vol. 25, no. 5, pp. 377–380, 2000. [8] S. Puavilai, S. Sriprachaya-Anunt, S. Charuwichitratana, A. Sakuntabhai, and N. Rajatanavin, “Etiology of erythema nodosum,” Journal of the Medical Association of Thailand, vol. 78, no. 2, pp. 72–75, 1995. [9] S. K. Wong and S. D. Yeung, “Erythema nodosum as the ﬁrst presenting complaint of asymptomatic pulmonary