Cryptococcal disease (cryptococcosis) is caused by Cryptococcus neoformans – Cryptococcus gattii complex, a ubiquitous environmental yeast that is endemic in many countries including Australia. Cryptococcosis is most often associated with human immunodeficiency virus (HIV) infection, but can also occur in immunocompetent individuals. The clinical manifestations of cryptococcosis are protean. Cryptococcal meningoencephalitis (CM) is the most frequent and most severe form with mortality rates of 20-70%; untreated this form is uniformly fatal. The most common route of acquisition is via inhalation, yet pulmonary cryptococcosis manifesting as lung infiltrates and cryptococcomas is poorly recognised. Less common again are skin cryptococcomas, ophthalmic, bone and prostatic cryptococcal disease. This chapter will focus on CM and pulmonary cryptococcosis.
An environmental organism with known clinical latency, the majority of infections are due to reactivation disease rather than acute infection. Risk factors for cryptococcosis include host immunodeficiency (steroids, CD4 depletion, other immunosuppressive host), geographical endemicity (including risk activities) and environmental outbreaks.
Cryptococcus spp. have a predilection to invade the central nervous system (CNS) leading to life-threatening meningoencephalitis.  Patients present with an acute, subacute or chronic meningitis or meningoencephalitis. Signs and symptoms include headache, nausea, fever, altered consciousness, cranial neuropathy, memory loss, confusion, meningeal irritation signs, nausea and vomiting, seizures, visual and hearing deficits and coma.      Signs associated with poor outcome include Glasgow coma scale (GCS) < 15, neurological deficit , confusion/ abnormal mental state/lethargy/obtundation, positive blood culture and high CSF cryptococcal antigen (CrAg).
The majority of patients with pulmonary cryptococcosis are asymptomatic or simply report cough, scant sputum production, fever, dyspnoea and chest pain, , ,  indistinguishable from other causes of pneumonia (reviewed in Chang et al.). Many present with an incidental radiological abnormality, mimicking lung malignancy.
Patients with cryptococcosis may be asymptomatic. Any patients with HIV infection presenting with subacute/ chronic headache, particularly those who are CD4-deplete, should be investigated for CM. Lumbar puncture should be performed to measure opening pressure, cerebrospinal fluid (CSF) cell counts, biochemistry and culture, CSF CrAg, Gram stain and India ink, along with serum CrAg, blood culture and chest X-ray. CT or MRI brain scans are helpful in assessing cryptococcomas, meningeal inflammation, vasculitis and ventricular compression.
Pulmonary cryptococcosis usually manifests as peripherally distributed lung nodules and masses are most common and more than 60% of patients have multiple nodules on chest X-ray and CT chest scan. Sputum and bronchoalveolar lavage often collected for culture may be negative. Culture and histology from lung biopsies provide a definitive diagnosis. Importantly isolation of the C. neoformans-C. gattii complex in respiratory samples should not be dismissed as contamination. Patients with any form of cryptcoccosis including pulmonary cryptococcosis should be comprehensively assessed with a serum CrAg, blood culture for dissemination, chest X-ray for pulmonary involvement and lumbar puncture for CNS involvement.
Regardless of the presence of symptoms, serum cryptococcal antigen testing should be performed in patients with new diagnosis of HIV - particularly those with advanced HIV and patients from countries where Cryptococcus spp. is endemic. The new lateral flow assay (LFA) for measuring cryptococcal antigen designed as a point-of-care test has performed well (> 95% sensitivity and 100% specificity) when used on serum and CSF, thus is comparable to the previously used latex agglutination test. The LFA assay is currently being used in a number of routine laboratories in Australia. A positive serum cryptococcal antigen test should trigger investigations for cryptococcoal dissemination – Chest XRay +/- CT chest, blood culture, a thorough skin examination and a lumbar puncture to diagnose CM.
Management of cryptococcal meningitis / meningoencephalitis
CM is a medical emergency requiring a diagnostic and therapeutic lumbar puncture, fluid resuscitation, airway management and early antifungal therapy. In resource-limited settings, 7.4% of patients die within the first 48 hours of hospital presentation – a reminder of its rapid lethality. The management of CM pivots on two major aspects: antifungal therapy and management of raised intracranial pressure. Antifungal therapy in cryptococcosis has been divided into three phases – induction, consolidation and maintenance. The induction phase is an area of intense research with regards to drug-dose combination and duration, as aggressive antifungal therapy has been shown to improve CSF culture sterility and be associated with improved clinical outcomes. The consolidation and maintenance phases are based on fluconazole therapy. Aggressive therapeutic lumbar punctures to relieve raised intracranial pressure are essential in the management of CM.
Antifungal treatment guidelines for cryptococcal meningitis
Current Infectious Diseases Society of America (IDSA) practice guidelines for treatment of CNS cryptococcosis in patients with HIV infection suggest a combination of conventional amphotericin 0.7-1.0 mg/kg/day and flucytosine (5-FC) 100 mg/kg/day as induction therapy for 2 weeks followed by 400 mg/day fluconazole as consolidation for a minimum of 10 weeks before reducing to a maintenance fluconazole dose of 200-400 mg/day. Alternative induction therapy include conventional amphotericin 0.7-1.0 mg/kg/day as a single agent for a prolonged 6-10 weeks duration or fluconazole 400-800 mg/day for 10-12 weeks. The Centre for Disease Control Morbidity and Mortality weekly report (CDC MMWR) 2009 guidelines on management of opportunistic infections endorse the amphotericin–5-FC approach, though they suggest a 0.7 mg/kg/day amphotericin dose, and recommend a minimum of 2 weeks of intensive therapy – prolonging intensive therapy until substantial clinical improvement and a ‘clearance’ culture-negative lumbar puncture is achieved. The 2011 World Health Organization WHO CM guidelines offer recommendations dependent on drug availability, with 2 weeks of 0.7-1.0 mg/kg of amphotericin and 100 mg/kg/day of 5-FC as their first choice, and 0.7-1.0 mg/kg of amphotericin and 800 mg of fluconazole as an alternative for induction therapy.
The IDSA guidelines are currently being rewritten and it is likely that a dose of conventional amphotericin 1.0 mg/kg/day and flucytosine (5-FC) 100 mg/kg/day will be endorsed as induction therapy as this combination has now been shown to have survival benefit over other antifungal combinations. The new Australian guidelines recommend 3 mg/kg/day liposomal amphotericin and 100 mg/kg/day of flucytosine as induction therapy. This recommendation is based on a small study demonstrating similar efficacy and reduced renal impairment when using liposomal amphotericin. Discontinuing maintenance therapy against prior cryptococcal infection is possible in individuals who remain asymptomatic and have a sustained increase in their CD4 T-lymphocyte (CD4) cell counts to > 200 cells/μL for at least 6 months after initiating antiretroviral therapy.
Amphotericin is associated with renal impairment, hypokalaemia and hypomagenesaemia, thus pre-emptive aggressive fluid, potassium and magnesium replacement is recommended. Flucytosine levels should be performed (detailed in Chau et al. ). A short list of possible side effects is in Table 1 (reviewed in Chau et al. ).
|Fluconazole||Mild to moderate nausea, vomiting, abdominal pain, diarrhoea Rash – may be associated with eosinophilia and pruritus Stevens-Johnson syndrome – rare, but may be fatal Increased liver function tests in 5-7% of patients Hepatic reactions including fulminant hepatic failure – rare Dizziness, headaches, alopecia|
|Conventional Amphotericin||Acute infusion-related reactions – fevers, chills, rigors, nausea and headache – common Anaphylaxis – rare Renal tubular abnormalities including renal tubular acidosis, hypokalaemia and renal impairment in up to 80% of patients Anaemia and cardiac arrhythmias|
|Liposomal Amphotericin||As for conventional amphotericin except less frequent|
|Flucytosine||Gastrointestinal intolerance, dose-related leukopenia and thrombocytopenia, rash, hepatitis, and peripheral neuropathy|
Management of raised intracranial pressure for CM
The majority of patients with CM have raised intracranial pressure (ICP). This increased pressure is associated with cognitive impairment, neurological defects and increased short-term mortality. Aggressive management of rapid ICP with therapeutic lumbar punctures is recommended in international CM guidelines based on the dramatic recovery in conscious states reported in early studies. Current recommendations for the management of raised ICP suggests repeated daily CSF drainage until opening pressure is stable, and drainage until CSF closing pressure is ≤ 20 cmH20 or < 50% of the initial opening pressure. Steroids have been used, mostly anecdotally in C. gattii infections, with no consistent result while acetazolamide has been clearly harmful in the management of CM.
Management of pulmonary cryptococcosis
There are no prospective studies on pulmonary cryptococcosis, thus treatment guidelines are based on retrospective case series, expert opinion and are inferred from studies of CM. Treatment guidelines from IDSA, the American Thoracic Society (ATS), the Australia and New Zealand Mycoses Interest Group (ANZMIG), World Health Organization (WHO) and other professional societies are summarised in Chang et al.
Overall, asymptomatic or mild-to-moderate pulmonary cryptococcosis may be treated with 400-800 mg fluconazole daily for 6-12 months while those with severe symptoms, diffuse infiltrates on imaging, and those with concomitant CNS disease should be treated as for CNS disease. Patients intolerant of fluconazole may be prescribed itraconazole 200-400 mg/day though there is growing anecdotal experience with the use of posaconazole and voriconazole in CM. Surgical resection should be considered in those with persistent symptoms despite therapy and those with very large pulmonary cryptococcomas (> 5 cm), particularly in the presence of a mass effect.
There have been two randomised studies of exogenous IFN-gamma as adjuvant therapy in CM but none in pulmonary cryptococcosis. Exogenous IFN-gamma showed no impact on mortality but was associated with a faster rate of CSF fungal clearance. Exogenous IGN-gamma is not currently used in routine clinical management of CM.
There is good randomised controlled trial evidence for the use of fluconazole or as second line, itraconazole 200 mg daily, as primary prophylaxis in patients with HIV infection with < 200 cells/μL CD4 cell counts, however uptake of this practice has been poor globally.
Timing of antiretroviral therapy commencement in cryptococcal meningoencephalitis co-infection
The timing of antiretroviral therapy commencement in the setting of any newly diagnosed opportunistic infection has been long debated where the risk of immune reconstitution inflammatory syndrome (IRIS) in early combination antiretroviral therapy (cART) commencement is measured against the ongoing risk of co-infections in late commencement. A number of studies have begun to address the optimal timing of antiretroviral therapy in CM-HIV co-infection with two small and one large randomised controlled trial cautioning against very early antiretroviral therapy initiation. A Zimbabwean randomised study was terminated early at 54 patients, after the early arm (72 hours) showed almost 3 times the risk of mortality of the delayed arm (> 10 weeks), adjusted HR 2.85, 95% CI 1.1-7.2. This study used 800 mg fluconazole as induction therapy and did not perform regular therapeutic lumbar punctures. A smaller, randomised study from Botswana of 27 patients, showed no difference in mortality but not unexpectedly, reported a significantly increased rate of cryptococcosis-associated IRIS (C-IRIS) (p = 0.002) in the early arm (median 7, IQR 5-10 days) compared to the late arm (median 32, IQR 28-36 days). The largest study on optimal antiretroviral commencement in CM (Cryptococcal Optimal ART Timing (COAT) study) was terminated at 35% of enrolment (n = 177), due to significantly increased 6-month mortality in the early arm (7-13 days) compared to the late arm (> 5 weeks) 45% vs. 30% (HR 1.7, 95% CI 1.1-2.8, p = 0.03) (COAT). The rate of C-IRIS was no different between arms 20% early vs. 13% deferred (p = 0.32).
Taken together, current evidence suggests that very early commencement of antiretroviral therapy (in the first 11 days after CM diagnosis) is likely harmful. Equally, deliberate delay of antiretroviral therapy commencement to > 5 or 6 weeks after CM diagnosis risks losses in follow-up. An unexplored time-window between 2-4 weeks of CM diagnosis remains. It is likely that patients could be risk-stratified – patients who demonstrate good clinical improvement, have normalised their CSF opening pressure and have sterilised their CSF are not likely to require a delay of > 5-6 weeks. Patients who have been able to sterilise their CSF (i.e. attain CSF culture negativity) prior to antiretroviral therapy commencement have improved clinical outcomes. The recent International Antiviral Society antiretroviral management guidelines suggest that initiating antiretroviral therapy early during CM treatment should be considered when expert management for both cryptococcal and HIV infection is available.
Neurological deterioration post- antiretroviral therapy commencement
Patients with CM are known to have symptomatic relapse despite being on adequate antifungal therapy and cART and may re-present with worsening headaches, new seizures or sudden loss of conscious state. The majority of these neurological deterioration episodes are thought to be due to C-IRIS (discussed in detail in Immune reconstitution inflammatory syndromes). Other differential diagnoses include cryptococcal microbiological relapse due to drug non-adherence, a new or undiagnosed second cause of meningitis such as tuberculosis meningitis and non-infective causes such as migraine or malignancy. Determining the cause of neurological deterioration is important as the management of each differs. A thorough history and examination, and a repeat lumbar puncture is recommended to measure opening pressure, and CSF should be sent for biochemistry, cell counts, cryptococcal culture and other molecular tests as necessary. In addition, brain imaging including CT and MRI scans may be necessary to look for focal brain lesions or meningeal enhancement.
Note that while CSF and serum cryptococcal antigen is often performed, this titre can remain high for many months, thus a high titre is not necessarily indicative of relapse disease. Similarly, a positive gram stain or India ink for Cryptococcus spp., is not necessarily indicative of microbiological relapse as dead Cryptococci are often seen for a prolonged period. A repeat positive CSF culture for Cryptococci suggests microbiological relapse, though comparative quantitative cultures done in research settings are more helpful – these are yet to be widely accepted in routine clinical work. Antifungal susceptibility testing is not routinely done in hospital laboratories but may be helpful in the setting of neurological deterioration.