Hypercalcaemia in Mycobacterium kansasii pulmonary infection

Area of Science:

• Nephrology
• Infectious Diseases
• Endocrinology

Background:

• Hypercalcemia is a complex metabolic disturbance often associated with malignancy, immobilization, and granulomatous diseases.
• In granulomatous conditions, hypercalcemia is typically attributed to overproduction of calcitriol by activated macrophages.
• Understanding the diverse etiologies of hypercalcemia is crucial for effective patient management.

Observation:

• A 60-year-old kidney transplant recipient presented with generalized weakness and altered mental status.
• Investigations revealed pancytopenia, acute kidney injury, hypercalcemia, low parathyroid hormone (PTH), and normal calcitriol levels.
• Chest CT showed lung opacities; bronchoscopy identified *Mycobacterium kansasii*.

Findings:

• The patient's hypercalcemia persisted despite normal calcitriol levels, challenging the classical understanding of calcitriol-mediated hypercalcemia in granulomatous disease.
• Treatment with bisphosphonates, calcitonin, and antibiotics for non-tuberculous mycobacterial pulmonary infection led to improved calcium levels.
• This case highlights a potential non-calcitriol-dependent mechanism for hypercalcemia in mycobacterial infections.

Implications:

• The findings suggest an alternative pathway for hypercalcemia in granulomatous infections, beyond calcitriol overproduction.
• This case broadens the differential diagnosis for hypercalcemia in immunocompromised patients, particularly transplant recipients.
• Further research is warranted to elucidate the precise mechanisms of hypercalcemia in mycobacterial infections.