Man with a Right Thigh Mass

Figure 1. MRI of the patient's right thigh showing intramuscular cysts (A, B) and CT of the patient's lungs showing a cavity with peripheral calcifications in right lung (C) and a densely calcified lesion in right lobe of the liver (D). Diagnosis: Multiorgan cystic echinococcosis (Hydatid cyst). The clue to the diagnosis was the presence of cystic thigh lesions and concomitant calcified hepatic and pulmonary le-sions in a patient who was continually exposed to an area in which echinococcosis is endemic. A unique feature of the current case is the radiographic demonstration of different stages of infestation: a calcified cyst, a cavitary lesion with rim cal-cification, and regular cysts (figure 1). Virtually any anatomic site can be affected by Echinococcus species. It most frequently affects the liver (in 50%–70% of cases) and lungs (20%–30%), but it can also affect other organs, such as the heart, the brain, and the bones (!10%) [1]. Involvement of thigh muscles is rare. The diagnosis was confirmed by an echinococcus IgG ELISA titer of 3.05 (normal value, р0.88). The absence of eosinophilia is typical, because this finding is usually present only when there is leakage of antigenic cyst fluid [2]. Our patient was PPD negative. Fungal serologic tests as well as fungal and mycobacterial stains and cultures had negative results. Echinococcosis is a zoonosis caused by larval stages (meta-cestodes) of cestodes that belong to the genus Echinococcus, family Taeniidae. Cystic echinococcosis is caused by Echino-coccus granulosus. Although knowledge of its global distribution is incomplete, it is present on all continents and is endemic in endemicity constitute an important risk group [4]. Dogs and other canids are the definitive hosts of Echinococcus species, whereas other mammals (typically ungulates, such as sheep) serve as intermediate hosts. Humans are not part of the natural cycle, but they can become aberrant or incidental hosts via ingestion of E. granulosus eggs. The clinical course of cystic echinococcosis is variable, ranging from rapid expansion with formation of daughter cysts and rupture into the biliary or bronchial tree to slow expansion, spontaneous collapse, and dense calcification of dead cysts [5]. Echinococcus multilocularis is the cause of alveolar echinococcosis. It is acquired from wild canids and is characteristically fulminant with a high mortality rate. Polycystic echinococcosis, caused by Echinococcus vogeli or Echinococcus oligarthrus, is restricted to South and Central America and is only rarely associated with human infection [6]. The diagnosis of echinococcosis …