Sarcoidosis and HTLV-1 infection

Human T-cell Lymphotropic Virus Type-1-associated Bronchioloalveolar Disorder with Non-necrotizing Granulomas: A Case Report and Literature Review

Human T-cell lymphotropic virus type-1 (HTLV-1)-associated bronchioloalveolar disorder (HABA) is a pulmonary disorder characterized by lymphocytic infiltration of the peribronchiolar space and interstitium in HTLV-1 carriers and in adult T-cell leukemia/lymphoma (ATLL). We herein report an 85-year-old woman carrying HTLV-1 with HABA who presented with a miliary pattern of micronodules in both lungs on high-resolution computed tomography and a lymphocytic infiltrate with non-necrotizing granulomas on pathology. This rare case of HABA should be differentiated from sarcoidosis, hypersensitivity pneumonitis, or miliary tuberculosis.

Etiologies of Sarcoidosis

Since sarcoidosis was first described more than a century ago, the etiologic determinants causing this disease remain uncertain. Studies suggest that genetic, host immunologic, and environmental factors interact together to cause sarcoidosis. Immunologic characteristics of sarcoidosis include non-caseating granulomas, enhanced local expression of T helper-1 (and often Th17) cytokines and chemokines, dysfunctional regulatory T-cell responses, dysregulated Toll-like receptor signaling, and oligoclonal expansion of CD4+ T cells consistent with chronic antigenic stimulation. Multiple environmental agents have been suggested to cause sarcoidosis. Studies from several groups implicate mycobacterial or propionibacterial organisms in the etiology of sarcoidosis based on tissue analyses and immunologic responses in sarcoidosis patients. Despite these studies, there is no consensus on the nature of a microbial pathogenesis of sarcoidosis. Some groups postulate sarcoidosis is caused by an active viable replicating infection while other groups contend there is no clinical, pathologic, or microbiologic evidence for such a pathogenic mechanism. The authors posit a novel hypothesis that proposes that sarcoidosis is triggered by a hyperimmune Th1 response to pathogenic microbial and tissue antigens associated with the aberrant aggregation of serum amyloid A within granulomas, which promotes progressive chronic granulomatous inflammation in the absence of ongoing infection.

Pulmonary sarcoidosis in an HIV/human T-cell lymphotrophic viruses I/II coinfected patient

Coexistence of HIV, pulmonary sarcoidosis, and human T-cell lymphotrophic viruses (HTLV) I/II has not been well reported and studied. Although the exact etiology of sarcoidosis is unknown, immunologic abnormalities have been the focus of human immunodeficiency virus (HIV)-related sarcoidosis and it is thought to be a manifestation of immune reconstitution inflammatory syndrome. We report the case of an African American woman with HIV and HTLV I/II coinfection who developed pulmonary sarcoidosis several months after the initiation of antiretroviral therapy. Despite the fact that most common etiologies of pulmonary nodules in HIV patients include mycobacterial and fungal infections, sarcoidosis should be considered in differential diagnosis. This disease may continuously rise due to the increasing number of people who are receiving antiretroviral therapy, leading to an improved immune system.

Role of resident CNS cell populations in HTLV-1-associated neuroinflammatory disease

Human T cell leukemia virus type 1 (HTLV-1), the first human retrovirus discovered, is the etiologic agent for a number of disorders; the two most common pathologies include adult T cell leukemia (ATL) and a progressive demyelinating neuroinflammatory disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The neurologic dysfunction associated with HAM/TSP is a result of viral intrusion into the central nervous system (CNS) and the generation of a hyperstimulated host response within the peripheral and central nervous system that includes expanded populations of CD4+ and CD8+ T cells and proinflammatory cytokines/chemokines in the cerebrospinal fluid (CSF). This robust, yet detrimental immune response likely contributes to the death of myelin producing oligodendrocytes and degeneration of neuronal axons. The mechanisms of neurological degeneration in HAM/TSP have yet to be fully delineated in vivo and may involve the immunogenic properties of the HTLV-1 transactivator protein Tax. This comprehensive review characterizes the available knowledge to date concerning the effects of HTLV-1 on CNS resident cell populations with emphasis on both viral and host factors contributing to the genesis of HAM/TSP.

Considering an infectious etiology of sarcoidosis

Sarcoidosis is a systemic granulomatous disease of unknown cause. An infectious etiology of sarcoidosis has long been suspected, but only recently has scientific evidence provided a strong link between infectious agents and sarcoidosis. Moreover, recent advances in our understanding of the relationships between sarcoidosis phenotype and host genetic factors may further illuminate the mechanisms linking infection and sarcoidosis.