Speckled-egg staining appearance of cryptococcal osteomyelitis in an immunocompetent patient

Abstract

Introduction: Cryptococcal infections are typically thought of as occurring in immunocompromised patients, such as patients with HIV/AIDS, solid organ transplant recipients, or patients with rheumatologic diseases that require immunomodulatory therapy. Moreover, Cryptococcus spp. classically appear as variably-sized yeasts with narrow-based budding surrounded by a thick polysaccharide capsule. However, cryptococcal infections are being increasingly reported in atypical hosts, at times with non-characteristic histochemical staining appearances. Herein, we report a case of cryptococcal osteomyelitis in an otherwise immunocompetent individual that had a "speckled-egg" staining appearance on direct-smear Gram stain.

Case: The patient is an otherwise healthy 89-year-old male with a past medical history notable only for hypertension who presented with progressive left-sided neck pain that became worse despite lidocaine trigger point injections; imaging was obtained and revealed a C1-C2 prevertebral abscess, C2-C4 osteomyelitis, and a small C2-C4 abscess. An aspiration biopsy from one of the cervical abscesses grew Cryptococcus neoformans. Despite prompt initiation of liposomal amphotericin B as soon as the organism was suspected, the patient's mentation declined with associated progression of weakness in his upper and lower extremities. The patient was ultimately transitioned to comfort care.

Conclusions: Unconventional presentations of cryptococcal disease are becoming increasingly recognized in seemingly immunocompetent patients. Our case was unique given that it occurred in a patient who appeared to be immunocompetent and the Gram stain showed a speckled-egg staining pattern that alone was not distinctive for cryptococcal yeasts. Despite the patient's lack of any classic comorbidities associated with invasive cryptococcal disease, his advanced age was likely a risk factor.

Keywords: Cryptococcal osteomyelitis; Cryptococcus neoformans; Histochemical staining; Immunocompetent.

Fig. 1

Speckled-egg appearance of Cryptococcus neoformans in a direct smear from the aspiration biopsy. Image collected at 1000x magnification (A), scale bar 20 µm (B).

Fig. 2

Crystal-lattice-like presentation of Cryptococcus on direct-smear of specimen (CSF) prepared via Gram stain. Image collected at 1000x magnification.

Fig. 3

Characteristic histopathological appearances of Cryptococcus neoformans in tissue (skin) via different stains: H&E (A), GMS (B), PAS (C), Fontana-Masson (D). Scale bars are all 20 µm; arrows in B and C indicate narrow-based budding, arrowhead in A indicates non-staining yeast within tissue space generated by non-staining capsule.