Cryptococcus neoformans osteomyelitis of the radius treatment with antifungal calcium sulphate: A case report and literature review

Abstract

Background: Cryptococcus neoformans is an opportunistic fungal pathogen widely distributed in nature, commonly found in soil and bird droppings such as pigeons. Cryptococcal osteomyelitis is usually found in immunocompromised patients, in an unusual condition Cryptococcus invades the bone. It usually occurs as a part of disseminated infection and is rarely isolated, and isolated cryptococcal osteomyelitis of the radius is rarer.

Case presentation: We report a case of a 41-year-old woman with no underlying disease who presented with progressive distal swelling of the left forearm. The patient was initially suspected by local doctors of a malignant bone tumor. For further diagnosis, we performed a computed tomography-guided biopsy of the radius and found granulomatous inflammation with massive macrophage infiltration and a specific stain showing mycosis. Genetic testing revealed a high abundance of Cryptococcus neoformans. We performed debridement of the radius and filled the bone defect with antifungal calcium sulfate. Fluconazole was taken orally for 3 months after operation. No recurrence was found in the 15-month follow-up.

Conclusion: It is the second case of Cryptococcus osteomyelitis as the only manifestation of extrapulmonary disease since 1973. It should be a safe and effective method to eliminate dead space, release antifungal drugs for a long time and increase bone stability by filling bone defect with antifungal drugs and calcium sulfate bone powder.

Keywords: Calcium sulfate; Case report; Cryptococcus; Fungus; Osteomyelitis; Radius.

Fig. 1

Anteroposterior and lateral x-ray findings of the left radius and ulna. Initial X-ray showed osteolytic damage to the diaphysis of the radius.

Fig. 2

Preoperative computed tomography. Non-enhanced CT scan (a coronal bone window, b sagittal bone window, c transverse bone window): osteolytic lesion surrounded by cystic low-density soft tissue mass.

Fig. 3

Preoperative magnetic resonance imaging (MRI). a: coronal T2-weighted; b: sagittal T2-weighted; c: sagittal T1-weighted; d: horizontal T1-weighted; e: horizontal T2-weighted; f: horizontal T2 lipoinhibition; g: horizontal magnetic susceptibility DWI.

Fig. 4

A: Puncture pathology shows: sheets of epithelioid tissue and scattered distribution of multinucleated giant cells, in which scattered distribution of round-like hyaline-like material is seen, interstitial fibrovascular hyperplasia with inflammatory cell infiltration, and localised sheets of degenerated and necrotic bone tissue are seen. b: NGS shows: Cryptococcus spp. Sequence number 512637, relative abundance 99.92 %; Cryptococcus neoformans sequence number 476239.

Fig. 5

Intraoperative details. a: after incision of the fascia, the mass was seen protruding from the dorsal aspect of the distal radius and adhering to the surrounding tendon sheath membrane; b: dorsal dorsal cortical defect on the lateral side of the radius. c: enlargement of the sinus tract for complete removal of the lesion; d: part of the mass is qualitatively similar to greyish-white fat in nature.

Fig. 6

Postoperative details. a: X-ray anteroposterior; b: X-ray lateral; c: CT coronal; d: CT sagittal; e–f: Postoperative histopathology showed: sheets of inflammatory granulation tissue and scattered distribution of multinucleated giant cells, in which scattered distribution of rounded hyaline-like fungal spores were seen, interstitial fibrovascular hyperplasia with infiltration of inflammatory cells, and localised sheets of necrotic bone tissue and birth blood were seen.

Fig. 7

Follow-up at 3-month postoperative. X-ray and CT showed: a decrease in density in the central portion of the bone powder filled area, peripheral degradation of the bone powder and production of new bone.

Fig. 8

Follow-up at 6-month postoperative. X-rays showed a decrease in density in the central portion of the bone powder filled area to a lesser extent, with new bone forming further from the periphery towards the centre.

Fig. 9

Follow-up at 15-month postoperative. X-rays show increased density in the bone powder filled areas, good new bone formation and high density relative to the surrounding area.