In this week’s post: A Crabby Situation- Diagnostic Dilemma, a question is posed regarding a patient from Indonesia with fevers and hemopytsis.

The solution is below…

The answer is F (Paragonimus westermani)

This was a case of Paragonamiasis, a parasitic infection caused by the lung fluke Paragonimus westermani.  It is notably seen in Southeast Asia amongst people who consume shellfish, especially crabs. This parasite initially infects snails, and after the embroynated miracidia convert to cercariae, they go on to infect shellfish such as crabs and crayfish, converting into metacercariae inside these hosts. It is at this point that this organism enters into mammalian hosts, primary through the consumption of undercooked shellfish that are infected. In the human gut, the metacercariae excyst, perforating through the small bowel and diaphragm and entering into the lungs, where they mature into adults and cause cavitary lung disease and inflammation. On presentation, this infection clinically and radiographically mimics pulmonary tuberculosis (TB). Unlike TB however, it is often associated with peripheral blood eosinophilia. Diagnosis is often made by biopsy, which reveal larvae in the lungs. The treatment is with praziquantel.

Mycobacterium avium can cause cavitary lung disease, however this organism causes slow, progressive lung changes which can take months to years to occur, unlike this patient where development of cavitary lung disease was relatively more acute. Cavitary Mycobacterium avium infection is also usually associated with chronic COPD, alcoholism and advanced age, none of which this patient had. Histoplasma dubosii, which causes African Histoplasmosis, is seen in the African continent as well as the island of Madagascar. It causes cutaneous as well as pulmonary findings, however given that the patient was from Indonesia, this diagnosis does not fit well with his clinical picture.  Strongylodies stercoralis can cause peripheral eosinophilia, however it does not classically cause cavitary lung disease or hemoptysis. Bronchoalveolar carcinoma of the lung usually presents with peripheral infiltrates on chest X-ray imaging, rather than cavitary disease, and classically grows along alveolar walls, sparing the lung parymchema. Given the above clinical picture, this diagnosis would be less likely than Paragonamiasis. Fasciola hepatica infection can cause eosinophilia, but is associated with visceral organ involvement and does not classically have pulmonary manifestations. This infection is acquired through the consumption of aquatic vegetation, such as watercress, which contain cysts of these parasites. Lastly, aspirated crab shells could produce an obstructive pneumonia over time and possibly even cavitary lung disease, but would not result in the peripheral eosinophilia that was noted, making this less likely.

The life cycle of this parasite is presented below:

 Source: CDC