Prepared by Osbert Egiebor, MD; Calvin Flowers, MD; Bradley
Langer, MD, Department of Radiology, Cook County Hospital,
A 44-year-old male presented with left chest discomfort
following a motor vehicle accident. His past medical history was
unremarkable, but his social history was significant for ingestion
of inadequately cooked snakes prior to emigration to the U.S. from
Africa 5 years before presentation. Physical examination was
unremarkable except for mild tenderness over the posterior left
fifth and sixth ribs. Hematologic profile and liver function tests
were normal. Radiographs of the chest and ribs were obtained by the
primary physician; an oblique radiograph of the lower chest and
upper abdomen is shown (figure 1). Due to these findings,
non-enhanced chest and abdominal CT images were obtained. What is
The oblique radiograph in figure 1 shows multiple ring-like and
cresentic calcific densities measuring 3 to 6 mm in size in both
hemithoraces and the upper abdomen. The differential diagnosis at
this time included cysticerci calcifications (usually oval with
lucent centers, arranged in the direction of muscle fibers),
granulomas, daughter cysts of hydatid disease (usually ring-like
calcifications), guinea worm calcification with an irregular coiled
appearance, and the thread-like calcifications of loa loa.
Non-enhanced computed tomography (CT) of the chest and abdomen
(figures 2,3) demonstrated the extensive ring-like and cresentic
calcifications involving the following: both lungs, the pleural and
pericardial surfaces, the liver, mesentery, omentum, the walls of
the stomach, and the small and large bowels. The patient was
discharged and prescribed a pain killer for possible
musculoskeletal strain. His symptoms subsequently resolved.
Pentastomiasis caused by
infestation is uncommon in developed countries.
usually infest the lungs of snakes such as vipers, pythons, and boa
constrictors. The three species of
important to humans include
restricted to West Africa;
seen in the Far East
typically found in the Western hemisphere. Pentastomiasis, which
presents classically with ring-like or cresentic soft-tissue
calcifications due to calcified porocephalida nymphs, is the most
frequent cause of chest and abdominal calcifications in endemic
Humans get infected after ingesting inadequately cooked snake, or
food and drink contaminated by the saliva of snakes containing the
The detailed life-cycle of the
parasite in humans is not well known, but the
nymphs have been found to cause significant disease because of the
worm burden, location, and tissue migration.
The nymphs usually are found in the subpleural and subperitoneal
spaces, the bowel walls, mesentery, and liver, resulting in a
severe granulomatous reaction due to host response. The sixth molt
of the nymph assumes a cresentic configuration in a fibrous capsule
which later dies and undergoes dystrophic calcification.
infestation usually is asymptomatic and is found incidentally at
radiological evaluations, surgeries, and autopsies.
The calcified nymphs are characteristically seen on radiographs as
multiple calcific densities which appear cresentic or linear en
face and ring-like in profile. These densities range from 3 to 8 mm
in size and have no particular alignment (figures 1-4). On CT the
calcified nymphs approximate the density of bone, with significant
streak artifacts which may simulate metallic foreign bodies
(figures 3A,3B). The highest concentration of the calcified nymphs
is in the upper abdomen due to extensive hepatic involvement. The
highest incidence of
infestation on plain radiographs is reported from Ibadan, Nigeria,
where 2% of adult males, 4% of adult females, and 1.4% of the
general population are affected.
This report is the first to document the CT features of
pentastomiasis and we would expect the incidence to be higher on CT
because it is more sensitive for the detection of calcification
compared to plain radiographs. The infestation incidence at autopsy
can be as high as 45%, as seen in Malaysian aborigines.
Although the parasitic infestation is commonly asymptomatic, it may
cause nodules in the lungs and the submucosal lining of the stomach
and jejunum mimicking tumors.
There is an association with a higher incidence of neoplasms,
and intestinal obstruction by fibrous bands.
When confronted with the chest or abdominal x-ray of a patient
with ring-like and cresentic calcifications from an endermic area,
and a history of ingestion of snakes or food and drink contaminated
by snakes' saliva, the possibility of pentastomiasis should be