Hypercalcaemia secondary to disseminated Mycobacterium abscessus and Mycobacterium fortuitum

Introduction

The environment is abundant in nontuberculous mycobacteria (NTM), but NTM rarely cause infection in immunocompetent humans. However, the incidence of NTM infections is increasing, and because of its diverse presentations diagnosis is often challenging.

Case presentation

A 68-year-old Singaporean Indian female with a past medical history of hypertension, hyperlipidaemia and minor stroke presented to us with 3 days of fever and dysuria. Physical examination was unremarkable. Basic investigation showed leucocytosis, high C-reactive protein, acute kidney injury, mild hypercalcaemia and deranged liver enzymes (Table 1). Chest X-ray revealed bilateral consolidation, while urinalysis showed pyuria. Empirical intravenous co-amoxiclav was initiated as treatment for possible sepsis from community-acquired pneumonia and urinary tract infection.

Table 1 Investigation results

Investigation	Result	Reference
White cell count	15.8 × 109/l	3.6–9.3 × 109/l
Haemoglobin	10.3 g/dl	11–15 g/dl
Platelet	362 × 109/l	170–420 × 109/l
Creatinine	179 µmol/l	40–75 µmol/l
C-reactive protein	211.7 mg/l	0–5 mg/l
Albumin	25 g/l	35–48 g/l
Bilirubin	10 µmol/l	7–31 µmol/l
Alanine aminotransferase	31 U/l	14–54 U/l
Aspartate aminotransferase	35 U/l	15–41 U/l
Alkaline phosphatase	268 U/l	38–126 U/l
Gamma glutamyltransferease	213 U/l	7–50 U/l
Hepatitis B surface antigen	Negative
Antihepatitis B core antibody	Negative
Antihepatitis C antibody	Negative
Prothrombin time	14.8 s	11.7–14 s
International normalised ratio	1.2
Adjusted calcium	2.77 mmol/l	2.15–2.58 mmol/l
Phosphate	1.0 mmol/l	0.8–1.6 mmol/l
Parathyroid hormone (intact)	1 pmol/l	0.8–6.8 pmol/l
25-hydroxy vitamin D (calcidiol)	23 µg/l	20–50 µg/l sufficient
Myeloma panel	No paraprotein
Angiotensin-converting enzyme	83 U/l	8–53 U/l
HIV	Negative
Thyroid function test	Normal
Chest X-ray	Bilateral consolidation
Induced sputum × 3 sets	Acid-fast bacilli stain: negative Tuberculosis culture: negative
Ultrasonography of abdomen	Diffuse heterogeneous echogenicity involving both lobes of the liver could be due to an infiltrative process such as diffuse metastases
Blood culture × 4 sets	Negative
Urine cultures	Negative

 

Both her parathyroid hormone and calcidiol levels were at the lower end of normal range. In the presence of hypercalcaemia with a relatively suppressed parathyroid hormone, disseminated malignancy was the top differential diagnosis at this stage. She was not taking medications or supplements that could lead to hypercalcaemia. Serum and urine protein electrophoresis showed no paraproteinaemia. An oesophago-gastro-duodenoscopy showed antral gastritis, while a colonoscopy revealed a few colonic polyps, the histology of which turned out to be tubular adenoma with low-grade dysplasia.

She subsequently underwent an ultrasound-guided liver biopsy. The histology showed necrotising granulomatous inflammation. The sample stained positive for acid-fast bacilli. Whilst awaiting the full culture results the patient was given a trial of tuberculosis (TB) treatment comprising isoniazid, rifampicin, pyrazinamide and ethambutol. Her hypercalcaemia was attributed to granulomatous disease and she was started on aggressive intravenous hydration. Despite this her calcium levels remained elevated at 2.7–2.9 mmol/l. She was given oral prednisolone 20 mg once daily for 2 weeks and her serum calcium level became normal at the end of steroid therapy. She was discharged with follow up with our TB Control Unit and her calcium levels were monitored in the outpatient clinic.

At her clinic appointment 6 weeks later, the tuberculous culture results were found to be negative. The liver tissue was also sent for a tuberculous nucleic acid amplification test (NAAT), which was also negative. The sensitivity of NAAT is high especially when the acid-fast bacilli smear is positive. It ranges between 96 and 98%.1 Three sets of induced sputum were negative for Mycobacterium tuberculosis. Despite the negative results, given the high prevalence of TB in South East Asia accounting for one-third of the TB cases in the world,2 TB was still top on the list of differentials and the patient was continued on anti-TB medications.

During her TB treatment, her calcium levels rebounded to 2.8 mmol/l. She was started on another course of steroids but her hypercalcaemia remained persistent. She was subsequently given one dose of intravenous zolendronic acid that resulted in normalisation of her calcium levels temporarily.

The TB treatment was given for 9 months but clinical response was poor. She continued to lose weight, her calcium level remained elevated, liver function tests continued to worsen (Table 2) and repeat CT scan showed increased pulmonary infiltrates and marginally bigger splenic and liver hypodensities.

Further investigations were performed to detect any evidence of immunodeficiency. HIV screen was negative. Antibodies against interferon-γ and antigranulocyte macrophage-colony stimulating factor were positive proving presence of adult-onset immunodeficiency.

Discussion

NTM are ubiquitous organisms that can be found in surface water, tap water, soil, domestic and wild animals, milk and food products.3 However, these organisms inhabit body surfaces and secretions without causing disease except in patients with chronic illnesses and immunodeficiency.

The most common NTM is Mycobacterium avium complex followed by M. abscessus complex and Mycobacterium kansasii.4 M. abscessus and M. fortuitum are classified as rapidly growing mycobacteria.

Disseminated NTM infections have been reported in the medical literature. Still NTM are often deemed as ‘benign’ infections and they are often not given the similar attention M. tuberculosis garners. NTM disease has an incidence rate of about 1.0–1.8 cases per 100,000 persons.5 As NTM is not a reportable disease in most countries, the true incidence of NTM infections is not known. Studies have shown increased and higher than anticipated incidence of NTM infections.6 The increased incidence may be attributed to greater exposure to large volume aerosols, the change in plumbing material and lower hot water temperatures.7 Often NTM infections are misdiagnosed as M. tuberculosis infections as NTM still remains a diagnosis of exclusion. Although NTM disease commonly affects the lungs, it can also cause lymphatic, skin and disseminated disease.

The American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA) have proposed a diagnostic criterion for NTM in a statement released in 2007 (Box 1).8

Box 1 American Thoracic Society and Infectious Diseases Society of America proposed diagnostic criteria for nontuberculous mycobacteria

There are various reasons why the initial cultures may have been negative. The agent used for sample decontamination can alter culture outcomes.9 Also, the choice of culture media is vital. Liquid media are in general more sensitive than solid media, such as used in our case.10 The culture media is incubated at a temperature of 35˚C, which is optimum for M. tuberculosis but not for NTM, which has optimum growth at the temperature of 30˚C.11 Some NTM organisms require enrichment of the culture medium to enhance growth.12

Deciding when to treat NTM is challenging. The concept of colonisation without infection is often used but remains unproven. If the physician opts not to treat the positive NTM result, the patient needs to be followed up to monitor for clinical features that may suggest active infection. Repeated positive culture results are a strong indication for treatment.

A literature search for cases of hypercalcaemia associated with M. abscessus and M. fortuitum did not yield any results. There are cases reported of M. avium complex-associated hypercalcaemia in immunocompetent and immunodeficient patients.

Mechanism of hypercalcaemia in NTM infections, as in other granulomatous diseases, is thought to be mediated by elevated calcitriol due to increased 1α hydroxylase activity from activated macrophages trapped in the pulmonary alveoli and granulomatous inflammation.13

Our patient’s calcidiol was at the lower end of normal range. Low calcidiol with elevated calcitriol has been described in patients with granulomatous disease.14 However, there are case reports on hypercalcaemic patients with M. avium complex and sarcoidosis with normal calcitriol levels suggesting that a relative excess of calcitriol is sufficient to cause hypercalcaemia.15 Calcitriol level was not checked for the patient in our case as it is costly and logistically challenging in the local setting. Also, it would not have aided in the diagnosis owing to the variability of calcitriol levels in granulomatous disease and the reliability of the assay and method used.16

Corticosteroids have been used in the treatment of hypercalcaemia secondary to granulomatous disease. Corticosteroids inhibit the conversion of calcidiol to calcitriol by 1-alpha-hydroxylase and also have anti-inflammatory effects on granulomas that produce vitamin D.17

However, there may be other mechanisms by which granulomatous diseases cause hypercalcaemia. A study has shown that expression of parathyroid-related peptide (PTHrP) is a feature of infectious granulomas regardless of aetiology or the tissue involved, suggesting that PTHrP expression is part of the normal granulomatous immune response.18 This may explain why the calcium levels in our patient showed poor response to the second course of steroids.

Adult-onset immunodeficiency has been reported to be associated with opportunistic infection, including NTM.19 Upregulation of interferon-γ after mycobacteria is phagocytosed by macrophages triggers neutrophils and macrophages to kill intracellular pathogens, including mycobacteria. This mechanism is important for the control of mycobacteria.20 Studies have shown cell-mediated immunodeficiency in HIV-negative subjects being caused by antibodies to interferon-γ. A cross-sectional study in Thailand of 20 cases of opportunistic infections in non-HIV subjects showed that all had antibodies to interferon-γ.21 A larger study of 203 patients in Thailand and Taiwan with opportunistic infections found that 88% of patients had neutralising anti-interferon γ antibodies.22

Conclusion

NTM infections need to be considered in patients with disseminated disease when investigations for TB are negative. There also are mechanisms in addition to increased calcitriol levels that contribute to hypercalcaemia in granulomatous disease.

1 Dinnes J, Deeks J, Kunst H et al. A systematic review of rapid diagnostic tests for the detection of tuberculosis infection. Health Technol Assess 2007; 11: 1–196.

2 Epidemiology, strategy, financing: WHO report. Geneva: World Health Organization; 2009 (WHO/HTM/TB/2009.411).

3 Falkinham JO 3rd. Epidemiology of infection by nontuberculous mycobacteria. Clin Microbiol Rev 1996; 9: 177–215.

4 Hoefsloot W, van Ingen J, Andrejak C et al. The geographic diversity of nontuberculous mycobacteria isolated from pulmonary samples: an NTMNET collaborative study. Eur Respir J 2013; 42: 1604–13.

5 Horsburgh CR Jr. Epidemiology of Mycobacterium avium complex. Mycobacterium avium complex infection: progress in research and treatment. Marcel Dekker 1996; 1–22.

6 Hermansen TS, Ravn P, Svensson E et al. Nontuberculous mycobacteria in Denmark, incidence and clinical importance during the last quarter-century. Sci Rep 2017; 7: 6696.

7 Baldwin SL, Larsen SE, Ordway D et al. The complexities and challenges of preventing and treating nontuberculous mycobacterial diseases. PLoS Negl Trop Dis 2019; 13: e0007083.

8 Griffith DE, Aksamit T, Winthrop K et al. An official ATS/IDSA Statement: diagnosis, treatment, and prevention of nontuberculous mycobacterial diseases. Am J Respir Crit Care Med 2007; 175: 367416.

9 Ferroni A, Vu-Thien H, Lanotte P et al. Value of the chlorhexidine decontamination method for recovery of nontuberculous mycobacteria from sputum samples of patients with cystic fibrosis. J Clin Microbiol 2006; 44: 2237–9.

10 Idigoras P, Beristain X, Iturzaeta A et al. Comparison of the automated nonradiometric Bactec MGIT 960 system with Löwenstein-Jensen, Coletsos, and Middlebrook 7H11 solid media for recovery of mycobacteria. Eur J Clin Microbiol Infect Dis 2000; 19: 350–4.

11 Schulze-Röbbecke R, Buchholtz K. Heat susceptibility of aquatic mycobacteria. Appl Environment Microbiol 1992; 58: 1869–73.

12 Saubolle MA, Kiehn TE, White MH et al. Mycobacterium haemophilum: microbiology and expanding clinical and geographic spectra of disease in humans. Clin Microbiol Rev 1996; 9: 435–47.

13 Om PS. Hypercalcemia in granulomatous disorders: a clinical review. Curr Opin Pulm Med 2000; 6: 442–7.

14 Burke RR, Rybicki BA, Rao DS. Calcium and vitamin D in sarcoidosis: how to assess and manage. Semin Respir Crit Care Med 2010; 31: 474–84.

15 Shrayyef MZ, DePapp Z, Cave WT et al. Hypercalcemia in two patients with sarcoidosis and Mycobacterium avium intracellulare not mediated by elevated vitamin D metabolites. Am J Med Sci 2011; 342: 336–40.

16 Malik H, Tristan R. Hypercalcaemia secondary to granulomatous disorders – a series. Endocrine Abstracts 2012; 28: P18.

17 Christine EP, Sujata S, Holly LG. A case of hypercalcaemia in an immunocompetent patient with Mycobacterium avium intracellulare. JRSM Open 2017; 8: 2054270417716614.

18 Joshua F, Douglas WB, Parviz H et al. Hypercalcemia in disseminated coccidioidomycosis: expression of parathyroid hormone-related peptide is characteristic of granulomatous inflammation. Clin Infect Dis 2012; 55: e61–6.

19 Pithukpakorn M, Roothumnong E, Angkasekwinai N et al. HLA-DRB1 and HLA-DQB1 are associated with adult-onset immunodeficiency with acquired anti-interferon-gamma autoantibodies. PLoS One 2015; 10: e0128481.

20 Fulton SA, Johnsen JM, Wolf SF et al. Interleukin-12 production by human monocytes infected with Mycobacterium tuberculosis: role of phagocytosis. Infect Immun 1996; 64: 2523–31.

21 Wongkulab P, Wipasa J, Chaiwarith R et al. Autoantibody to interferon-gamma associated with adult-onset immunodeficiency in non-HIV individuals in Northern Thailand. PLoS One 2013; 8: e76371.

22 Browne SK, Burdelo PD, Patel SY et al. Adult onset immunodeficiency in Thailand and Taiwan. N Engl J Med 2012; 367: 725–34.