Disseminated Mycobacterium kansasii Infection in a Patient With Silicosis, Pulmonary Alveolar Proteinosis, and Myelodysplastic Syndrome

Abstract

Introduction: Mycobacterium kansasii is a nontuberculous mycobacterium that causes pulmonary infection in patients with predisposing chronic lung conditions and disseminated infection in immunocompromised hosts. We describe a patient with pulmonary silicosis, persistent unexplained anemia, disseminated M kansasii infection, and pulmonary alveolar proteinosis (PAP). CASE PRESENTATION: A 42-year-old Caucasian male with a 15-year history of occupational exposure to silica and 36 pack-year smoking history developed Guillain-Barre Syndrome (GBS), which resolved with intravenous immunoglobulin. Over the next three years his lung function deteriorated. Lung biopsies showed silicotic nodules and occasional non-necrotizing granulomas. Three years after his initial presentation, he was admitted to hospital with weight loss, fever, hypoxia, dehydration, and pancytopenia. Bone marrow biopsy revealed hypocellular marrow with decreased megakaryocytes. Sputum, pleural fluid, and blood cultures grew M kansasii. He died from complications of sepsis. Postmortem findings included PAP, extensive silicotic nodules in the lungs and thoracic and abdominal lymph nodes, and disseminated fulminant necrotizing M kansasii infection. Bone marrow chromosome analysis, which did not become available until after the patient's death, revealed monosomy 7, compatible with myelodysplastic syndrome (MDS), unclassifiable. DISCUSSION: The patient had a number of risk factors for disseminated M kansasii infection, including MDS, silicosis, and PAP. Clinical notes suggest a family history of agranulocytosis raising the possibility of an underlying genetic myelodysplasia. Monocytopenia and mycobacterial infection (MonoMAC) is a recently described syndrome consisting of profound monocytopenia with susceptibility to disseminated nontuberculous mycobacterial, viral, and fungal infections. MonoMAC is associated with missense mutations of the GATA2 gene, a predisposing gene for familial MDS and acute myeloid leukemia (AML). MonoMAC provides a potential unifying diagnosis linking this patient's MDS, PAP, and disseminated M kansasii infection. Genetic testing on preserved nerve tissue has been requested. Conclusions: The cause of this patient's deterioration in lung function over several years is unclear. Silicosis is not generally associated with well-defined granulomas in the lung. Perhaps MonoMAC produces a granulomatous interstitial lung disease similar to that seen in other immunodeficiency syndromes, such as common variable immunodeficiency (CVID). Although MonoMAC is rare, it should be considered in patients with a triad of myelodysplasia, PAP, and disseminated mycobacterial, fungal or viral infections.