Acute appendicitis is the most common abdominal emergency in many parts of the world. The lifetime risk has been estimated at almost 10% [1]. The incidence of appendicitis was strongly age dependent, peaking at 10–14 years [2].

Nevertheless, we report a rare case of simultaneous acute appendicitis in identical twins.

Physical examination of the patient revealed normal pulse rate, blood pressure, respiratory rate and body temperature. The abdomen was soft, tenderness and rebound tenderness were noticed in the right iliac fossa. Mcburney, Rovsing and Psoas signs were positive.

Laboratory tests revealed increasing in neutrophils 85%, CRP 85.9 mg/l, ESR 67 mm for 1st hour, 111 mm for 2nd hour and decreasing in lymphocytes 9.6%, hemoglobin 8.5 g/dl, red blood cell count 3x10⁶/cm³, hematocrit 26.2% and normal white blood cell count 5900/cm³, mean corpuscular volume 87 fl. Ultrasound was inconclusive (Figure 1).

The diagnosis was uncertain so that she had a laparoscopic surgery. She had appendicitis and appendectomy was done. She made an uneventful post-operative recovery and was discharged on the next postoperative day.

It was surprising that the identical twin presented within 36 hours after her sister with the same complaints in addition to fever and sweating for six hours too. She denied any chills, diarrhea/constipation or urinary symptoms. She had no significant past medical history.

Physical examination of the patient was similar to her sister (Case 1) except that her body temperature was elevated 38.5°C.

Laboratory tests revealed increasing in neutrophils 78.5%, CRP 78.6 mg/l, ESR (57 mm for 1st hour, 103 mm for 2nd hour) and decreasing in hemoglobin 9.9 g/dl, red blood cell count 3.52x10⁶/cm³, hematocrit 30.4% and normal white blood cell count 5500/cm³, mean corpuscular volume 86 fl. Ultrasound was inconclusive too (Figure 2).

The surgeon suspected appendicitis like her twin so that she had surgery and appendectomy was done. She also made a good postoperative recovery and was discharged on the second postoperative day.

Simultaneous cases of acute appendicitis are extremely rare and only five cases have been reported in literature [3]. All of the twins evaluated in the literature presented in the first or second decade within a day of each other. Although the South African twins presented slightly further apart, it is interesting that both were pyrexial and did not show leukocytosis [3].

Genetic factors have been implicated in the etiology of acute appendicitis [4]. Basta et al. demonstrated a familial aggregation and polygenic transmission pattern in a retrospective analysis of families of 80 patients with appendicitis when compared to families of matched controls [4]. The familial tendency to acute appendicitis may perhaps be explained by environmental factors such as a specific bacterial infection, certain food habits, or a genetic difference in resistance to bacterial infection [4]. However, the cause of appendicitis remains elusive and familial factors are of variable influence [1].

In our case report, the Caucasian twins were in the third decade and presented within 36 hours of each other. It was interesting that both complained of general abdominal pain and their abdominal examination was the same. They also showed normal white blood cell count but increasing in neutrophils.

The literature needs more reported cases of simultaneous appendicitis in monozygotic twins to deduce whether genetics or coincidence is responsible for this presentation [3].

Identical twins are not only similar in the morphologic features, it seems to be that there is a heredity predisposition for diseases not only the chronic diseases but also the acute one such appendicitis. This raises question to the extent of acute diseases which twins may really have a genetic predisposition for it.

1. Sadr Azodi O, Andrén-Sandberg A, Larsson H. Genetic and environmental influences on the risk of acute appendicitis in twins. Br J Surg 2009 Nov;96(11):1336–40.   [CrossRef]   [Pubmed]    
2. Andersson R, Hugander A, Thulin A, Nyström PO, Olaison G. Indications for operation in suspected appendicitis and incidence of perforation. BMJ 1994 Jan 8;308(6921):107–10.   [CrossRef]   [Pubmed]    
3. Haji A, Liao C. Acute appendicitis in identical twins. The Internet Journal of Surgery 2005;8(2).    
4. Ergul E. Heredity and familial tendency of acute appendicitis. Scand J Surg 2007;96(4):290–2.   [CrossRef]   [Pubmed]