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Differential Diagnosis

There is no other calcification likely to prevent the radiologist from making the correct diagnosis when the characteristic long linear, serpiginous or coiled, whorled "chain mail" types of calcification are present in the soft tissues. Several filarial worms, particularly Loa loa and Onchocerca volvulus, may calcify, but these are much smaller and almost always seen in the hands and feet. Either may cause small, coiled masses of calcification and occasionally may be linear, but neither is as large or extensive as the guinea worm.

The calcification of Armillifer nymphs is crescentic or ring-like, and these tiny 3-6 mm calcifications are always in the abdomen and thorax and never in the subcutaneous tissues. Calcified cysticerci of Taenia solium are invariably numerous and typically oval or fusiform; they are only about 1 cm in length and are quite easy to identify and distinguish from Dracunculus medinensis.

Only the amorphous dystrophic pattern of calcification, seen when the guinea worm dies with severe reaction about it, causes problems in diagnosis. This pattern of calcification can be mistaken for a pulmonary granuloma when it overlies the chest wall (Fig. 27.20), or calcification within lymph nodes (as occurs in tuberculosis), or other causes of localized soft tissue calcification. However, its smooth outline and almost inevitable association with calcified guinea worms elsewhere in the body will permit its true identification. At times, a calcified worm may be seen on films of the abdomen or pelvis in the vicinity of the bladder and, unless the possibility of dracunculiasis is remembered, it may be mistaken for calcification within pelvic vessels, the vas deferens, or the bladder. Soft tissue radiographs of other areas of the body will usually show other calcified worms in more typical locations.

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Fig. 27.20. A Calcified guinea worm in a patient from Saudi Arabia simulating an intrapulmonary granuloma in the left upper lobe on posteroanterior view of the chest. However, on close inspection, the serpiginous nature of the calcification can be seen, and on coned lateral view of the anterior chest wall, the calcified worm is seen in subcutaneous tissues overlying the ribs (B). (Courtesy of Dr. John Ebersole, Lancaster) C Calcified guinea worm in the chest wall of a patient from India. A portion of the worm shows serpiginous calcification while dense dystrophic calcification surrounds the remainder of the worm. (Courtesy of Dr. A. Chandrahasan Johnson).

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