Applied Radiology

Diagnosis

Omental cryptococcosis related to HIV infection

Discussion

Cryptococcosis is a subacute or chronic fungal infection. The organism, Cryptococcus neoformans, is an encapsulated yeast-like fungus that has been found in infected pigeon droppings with airborne dispersion. The infection is acquired via the respiratory route, with a primary focus in the lung. Characteristically, it then spreads to the central nervous system. Additionally, bone and skin lesions are seen in up to 10% of cases. Cutaneous lesions appear as acneiform pustules or granulating ulcers. Other, more rare sites of infection are the breast, adrenal glands, kidney, prostate, liver, heart, and thyroid. The primary pulmonary infection may be minimal, with little or no symptoms, and may regress spontaneously. Cryptococcosis with no detectable pulmonary lesions, even at autopsy, has been seen, as was the case with our patient. Chest x-rays of the patient showed no abnormality. Subsequently, the patient was found to have C. neoformansin his cerebrospinal fluid.

Reports of abdominal CT findings in patients with HIV infection and fungal infection are few. Radin reported on abdominal findings in HIV positive patients with fungal infections, including cryptococcosis, with CT scans showing splenomegaly, enlarged lymph nodes, and hepatomegaly.¹ Infiltration of the mesentery was not seen in Radin's series. Additionally, one reported case of histoplasmosis involving the omentum in an AIDS patient is noted in the radiological literature.² There also has been one reported case of omental cryptococcoma in pathology literature in an otherwise healthy young man with no underlying illnesses.³ In non-AIDS patients, thickened omentum can be caused by neoplasms, most commonly due to lymphoma and metastases. Peritoneal cavity infection secondary to ruptured viscus or secondary to blood- or lymphatic-borne infection also can produce thickening of mesentery, and trauma adjacent to or involving the mesentery can produce infiltration and thickening of the omentum.⁴

1. Radin R:HIV Infection: Analysis in 259 consecutive patients with abnormal abdominal CT findings. Radiology 197:712-722, 1995.
2. Alterman DD, Cho KC: Histoplasmosis involving the omentum in an AIDS patient: CT demonstration. J Comput Assist Tomogr 12:664-665, 1988.
3. Chong PY, Panabokke RG, Chew K: Omental cryptococcoma. Arch Path Lab Med 110:239-241, 1986.
4. Ruess L, Frazier A, Sivit C: CT of the mesentery, omentum and peritoneum in children. Radiographics 15:89-104, 1995.