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Patella is an uncommon site for the occurrence of bone tumor. Benign tumors are more common as compared to malignant ones. Osteosarcoma of the patella is a very rare tumor with only a few cases reported in the literature. Here, we present a rare case of a small-cell variant of osteosarcoma of the patella. A 12-year-old boy presented to us with pain and swelling over his left knee for 6 months. On X-ray, expansion with osteosclerotic and osteolytic lesions was found in the patella and a suspected diagnosis of osteosarcoma was made. The patient was managed by excisional biopsy of the patella and V–Y plasty of the quadriceps tendon. Results of histopathological and immunohistochemistry analyses were consistent with osteosarcoma of small cell variant. The patient was referred to a higher center after the operation for radiotherapy and chemotherapy. On the final follow-up, after 1 year, the patient was found to have expired. Osteosarcoma of the patella is a rare condition. Further studies with a number of cases and longer duration of follow-up are warranted to obtain better insight that can aid in devising management protocol, prediction of survival, and functional outcome of different surgical interventions for these patients.

Patella is an uncommon site for the occurrence of bone tumor. Benign tumors are more common as compared to malignant ones. Osteosarcoma of the patella is a very rare tumor with only a few cases reported in the literature. Here, we present a rare case of a smallcell variant of osteosarcoma of the patella. A 12-year-old boy presented to us with pain and swelling over his left knee for 6 months. On X-ray, expansion with osteosclerotic and osteolytic lesions was found in the patella and a suspected diagnosis of osteosarcoma was made. The patient was managed by excisional biopsy of the patella and V-Y plasty of the quadriceps tendon. Results of histopathological and immunohistochemistry analyses were consistent with osteosarcoma of small cell variant. The patient was referred to a higher center after the operation for radiotherapy and chemotherapy. On the final follow-up, after 1 year, the patient was found to have expired. Osteosarcoma of the patella is a rare condition. Further studies with a number of cases and longer duration of follow-up are warranted to obtain better insight that can aid in devising management protocol, prediction of survival, and functional outcome of different surgical interventions for these patients. [ABSTRACT FROM AUTHOR]

Simple Summary: Anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL) is an aggressive T-cell lymphoma characterized by large T-cells with strong CD30 and ALK expression. Approximately 30% of patients treated with conventional chemotherapy experience a relapse or refractory disease and have a poor prognosis. Several risk factors associated with poor prognosis have been identified in pediatric ALK-positive ALCL, such as the morphological pattern of the small cell variant or lymphohistiocytic variant, leukemic presentation, the presence of minimal disseminated disease, or involvement of the central nervous system. Relapsed or refractory ALK-positive ALCL requires salvage therapy. Recently, targeted therapies such as ALK inhibitors and brentuximab vedotin have demonstrated dramatic responses in chemoresistant ALK-positive ALCL. Hematopoietic stem cell transplantation has also been reported to be an effective therapy. This article reviews pediatric ALK-positive ALCL, focusing on the risk factors associated with poor prognosis and treatment strategies for relapsed or refractory disease. Anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL) is an aggressive T-cell lymphoma characterized by large T-cells with strong CD30 and ALK expression. Although conventional chemotherapy is effective in most patients, approximately 30% experience a relapse or refractory disease and have a poor prognosis. Several risk factors associated with poor prognosis have been identified in pediatric ALK-positive ALCL. These include morphological patterns with the small cell variant or lymphohistiocytic variant, leukemic presentation, the presence of minimal disseminated disease, or involvement of the central nervous system. Relapsed or refractory ALK-positive ALCL is often resistant to conventional chemotherapy; therefore, salvage therapy is required. In recent years, targeted therapies such as ALK inhibitors and brentuximab vedotin (BV) have been developed. ALK inhibitors block the continuous activation of ALK kinase, a driver mutation that leads to cell proliferation in ALK-positive ALCL. Additionally, BV is an antibody–drug conjugate that targets CD30-positive cells. Both ALK inhibitors and BV have displayed dramatic effects in chemoresistant ALK-positive ALCL. Weekly vinblastine treatment and hematopoietic stem cell transplantation have also been reported to be effective therapies. This article reviews pediatric ALK-positive ALCL, focusing on risk factors and treatment strategies for pediatric patients with relapsed or refractory ALK-positive ALCL. [ABSTRACT FROM AUTHOR]

Abstract Background Many gram-negative bacteria produce an outer membrane phospholipase A (PldA) that plays an important role in outer membrane function and is associated with virulence. Results In the current study, we characterized a pldA mutant of Coxiella burnetii, an intracellular gram-negative pathogen and the agent of human Q fever. The C. burnetti pldA open reading frame directs synthesis of a protein with conserved PldA active site residues. A C. burnetii ΔpldA deletion mutant had a significant growth defect in THP-1 macrophages, but not axenic medium, that was rescued by complementation. Thin layer chromatography was employed to assess whether pldA plays a role in remodeling membrane lipids during C. burnetii morphological differentiation. Extracted lipids were analyzed from replicating, logarithmic phase large cell variants (LCVs), non-replicating, stationary phase small cell variants (SCVs), and a mixture of LCVs and SCVs. Similar to Escherichia coli, all three forms contained cardiolipin (CL), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). However, PE and PG were present in lower quantities in the SCV while three additional lipid species were present in higher quantities. Co-migration with standards tentatively identified two of the three SCV-enriched lipids as lyso-phosphatidylethanolamine, a breakdown product of PE, and free fatty acids, which are generally toxic to bacteria. Developmental form lipid modifications required the activity of PldA. Conclusions Collectively, these results indicate developmentally-regulated lipid synthesis by C. burnetii contributes to colonization of macrophages and may contribute to the environmental stability and the distinct biological properties of the SCV.

Primary central nervous system (CNS) anaplastic large cell lymphoma (ALCL) is an uncommon type of brain tumor, usually treated with a regimen that includes high-dose methotrexate (MTX). Only a few cases of primary CNS anaplastic lymphoma kinase (ALK)–positive ALCL have been reported so far, with no reported cases of a small cell variant. A 26-year-old man presenting with headache and visual field impairment was found to have a supratentorial mass mimicking meningioma. Craniotomy was performed for tumor resection, and postoperative histologic examination revealed atypical cells that were nonenlarged lymphocytes with irregularly shaped and enlarged nuclei; these cells were cluster of differentiation 30 and ALK -positive, leading to the diagnosis of a small cell variant of ALK -positive ALCL. In this case, the tumor exhibited an aggressive behavior with MTX resistance with metastases in the pelvis but responded well to cytarabine and etoposide (CYVE). In general, CNS ALK -positive ALCL responds well to MTX, but small cell variants show aggressive behavior and may be resistant to MTX. For small cell variants of ALCL that are resistant to MTX therapy, as in this case, CYVE therapy may be an effective treatment. [ABSTRACT FROM AUTHOR]

Numerous small lymphocytes with lobulated nuclei represent "cerebriform cells or flower cells" (arrows), and a few large lymphocytes with basophilic cells with vacuolated cytoplasm represent "hallmark cells" (arrowheads). Keywords: nucleophosmin-anaplastic lymphoma kinase; small cell variant; anaplastic lymphoma kinase-positive anapestic large cell lymphoma; leukaemic phase; droplet digital polymerase chain reaction EN nucleophosmin-anaplastic lymphoma kinase small cell variant anaplastic lymphoma kinase-positive anapestic large cell lymphoma leukaemic phase droplet digital polymerase chain reaction 241 243 3 12/27/21 20220101 NES 220101 The small cell variant of anaplastic large cell lymphoma (SC-ALCL) is a subtype showing unfavourable prognosis and accounting for 6% of ALCLs.1 SC-ALCL is defined as comprising two distinct tumour cell populations in immunohistochemistry: small cells staining negative or weakly positive for anaplastic lymphoma kinase (ALK) and cluster of differentiation 30 (CD30) protein; and large cells staining strongly positive for those proteins.2-4 Although the constitution of these two different cell populations might contribute to the poor prognosis, detailed characterisation of each population by molecular-based approaches has not been done due to the difficulty of cell separation from solid tumour samples. Characterisation of two tumour cell populations in the small cell variant of anaplastic lymphoma kinase-positive anaplastic large cell lymphoma. [Extracted from the article]

Anaplastic large cell lymphoma (ALCL) is a rare disease accounting for 10%–15% of all non-Hodgkin's lymphomas in children. It is distinguished from other lymphomas by their anaplastic cytology and constant membrane expression of the CD30 antigen. We report a 9-year-old boy presented with a left calf swelling. Biopsy from swelling revealed as small cell variant of anaplastic lymphoma kinase-positive ALCL. Staging with positron emission tomography–computed tomography showed lymph nodal and multiple extra-nodal involvement. The extra-nodal sites were lung, pancreas, bone, sphenoid sinus and muscles. He was started on ALCL-99 protocol.

Anaplastic large cell lymphoma (ALCL) is a rare disease accounting for 10%–15% of all non‑Hodgkin’s lymphomas in children. It is distinguished from other lymphomas by their anaplastic cytology and constant membrane expression of the CD30 antigen. We report a 9‑year‑old boy presented with a left calf swelling. Biopsy from swelling revealed as small cell variant of anaplastic lymphoma kinase‑positive ALCL. Staging with positron emission tomography–computed tomography showed lymph nodal and multiple extra‑nodal involvement. The extra‑nodal sites were lung, pancreas, bone, sphenoid sinus and muscles. He was started on ALCL‑99 protocol. [ABSTRACT FROM AUTHOR]

The small cell variant renal oncocytoma is until now a rarely described and easily misdiagnosed subtype of renal oncocytoma. The tissue morphology, immunohistochemical profile, ultrastructural and molecular characteristics of four cases of small cell variant renal oncocytoma were analyzed and the literature was reviewed. The patients were three women and one man with ages ranging from 51 to 76 years. The size of the tumors ranged from 3 to 8.5 cm in diameter. The follow-up duration ranged from 6 to 58 months. All patients lived uneventfully without tumor recurrence or metastasis. The tumors were grayish yellow to brown, well demarcated, with a central scar or cystic change. Microscopically, the tumor was arranged in lobular structure containing dense small acini or tubular structures, with small cells featuring weak eosinophilic and scant cytoplasm, small round nuclei and inconspicuous nucleoli. No mitotic figures or necrosis were discerned. The immunohistochemical profile of small cell variant of renal oncocytoma is partially consistent with classic oncocytoma, expressing EMA, CK18, CD117 and E-cad. However, MITO and S-100A1 were intensively expressed in classic RO, but neither of them was expressed in small cell variant RO. Ultrastructurally, a small number of organelles was revealed in the tumor cell, including a few mitochondria, lysosomes and microvilli, less than those in the classic oncocytoma. No genetic aberrations were found in all cases regardless of clinicopathological characteristics and tissue types. Small cell variant renal oncocytoma of the kidney is frequently difficult to be differentiated from other benign and malignant small cell tumors with eosinophilic cytoplasm. The immunohistochemical profile, ultrastructural and genetic features of the tumor are integrally presented here for the first time. Acquaintance with the special characteristics of the tumor could facilitate the correct diagnosis of the tumor. [ABSTRACT FROM AUTHOR]

This study aimed to describe the clinical features and outcome of anaplastic large cell lymphoma ( ALCL) with leukaemic presentation in children. Among 267 patients included in the French paediatric ALCL database between 1989 and 2012, nine (3%) were described as having cytologically detectable circulating tumour cells. Clinical features combined fever (8/9), nodal and extra-nodal disease (9/9), including hepato-splenic (9/9) and lung involvement (7/9). The level of hyperleucocytosis ranged from 30 to 120 × 109/l, with 12-90% of tumour cells. Diagnosis relied on a lymph node biopsy, with a positive ALK+ antibody immunostain in all nine cases, a T-cell immunophenotype in 7/9 cases and CD3 positivity in 5/9 cases. A small cell component was present in 6/9 cases. Only four patients achieved a complete remission with first-line therapy and 3/4 relapsed. Four patients are alive with a median follow-up of 31 months, two of them after allogeneic haematopoietic stem cell transplantation ( HSCT), and five patients died, two of them of disease. In conclusion, ALCL with leukaemic presentation is very unusual and should be considered as high-risk lymphoma requiring new therapeutic strategies. The respective role of new agents and allogeneic HSCT in first complete remission still has to be assessed. [ABSTRACT FROM AUTHOR]

The small cell variant of anaplastic large cell lymphoma (ALCL) presents in a nearly identical manner to the more common ALK primary ALCL, with the exception that it is more frequently associated with leukemic involvement, and the prognosis has been reported to be poor. We report a 40-year-old Japanese male who was diagnosed with small cell variant ALCL with peripheral blood involvement stage IVB, age-adjusted international prognostic index 3. Conventional cytogenetics of the bone marrow aspirate specimen showed abnormal metaphases with the following karyotype: 47, XY, +X, t(2;5)(p23;q35). The patient was treated with acute lymphoblastic leukemia-oriented intensive chemotherapy. He underwent allogeneic peripheral blood stem cell transplantation from his HLA-DR1 locus mismatch sister. Prior to transplant, the patient had residual lymphadenopathy considered to be in partial remission. As of August 2012, the patient has achieved 18 months of continuous complete remission (CCR), with a Karnofsky score of 100 %. We have identified a total of seven cases of small cell variant ALCL treated with allogeneic hematopoietic stem cell transplantation (HSCT) in the literature. Of these, no relapse was reported, and four patients were CCR more than 1 year. Allogeneic HSCT appears to represent a promising treatment option for small cell variant ALCL. [ABSTRACT FROM AUTHOR]

Abstract: ALK-positive anaplastic large cell lymphoma (ALK+ ALCL) is an uncommon non-Hodgkin''s lymphoma of T-cell origin, the majority of which express CD4 and show frequent pan-T-cell antigen loss. While most cases of ALK+ ALCL have the common pattern characterized by anaplastic morphology with hallmark cells, a less common but well-recognized variant with a small cell pattern may pose a diagnostic challenge. We report a case of ALK+ ALCL with small cell morphology and CD8 subset restriction in a 53-year-old male patient who presented primarily with multiple recurrent subcutaneous nodules with histopathologic features simulating a subcutaneous panniculitis-like T-cell lymphoma (SPTCL). The case was initially diagnosed as SPTCL but was reconsidered as ALK+ ALCL when the incidental finding of CD30 positivity on a subsequent biopsy prompted an ALK immunostain, which turned out to be positive in the neoplastic T-cells. The diagnosis of ALK+ ALCL, small cell variant, was then confirmed by detection of an ALK gene rearrangement by FISH analysis. This report highlights a case of ALK+ ALCL with a deceiving clinical and histopathologic presentation, and emphasizes the value of immunohistochemical panel studies and genetic tests in such cases to avoid diagnostic errors. [Copyright &y& Elsevier]

Anaplastic large cell lymphoma (ALCL) is a distinct type of T/null-cell non-Hodgkin lymphoma that commonly involves nodal and extranodal sites. The World Health Organization of lymphoid neoplasms recognizes two types: anaplastic lymphoma kinase (ALK) positive or ALK negative, the former as a result of abnormalities involving the ALK gene at chromosome 2p23. Patients with ALCL rarely develop a leukemic phase of disease, either at the time of initial presentation or during the clinical course. Described herein is a patient with ALK+ ALCL, small cell variant, associated with the t(2;5)(p23;q35), who initially presented with leukemic involvement and an extraordinarily high leukocyte count of 529 × 109/L, which subsequently peaked at 587 × 109/L. Despite chemotherapy the patient died 2½ months after diagnosis. In the literature review 20 well-documented cases are identified of ALCL in leukemic phase reported previously, with a WBC ranging from 15 to 151 × 109/L. Leukemic phase of ALCL occurs almost exclusively in patients with ALK+ ALCL, most often associated with the small cell variant and the t(2;5)(p23;q35), similar to the present case. Patients with leukemic phase ALK+ ALCL appear to have a poorer prognosis than most patients with ALK+ ALCL. [ABSTRACT FROM AUTHOR]

Because of the rarity and the morphological variations, small cell variant of anaplastic large cell lymphoma (ALCL) represents a diagnostic challenge. Herein is reported a case of leukemic type of small cell variant of ALCL, in which the diagnosis was established by a cytogenetic analysis. The patient was a 23-year-old woman who presented with fever and leukocytosis with circulatory atypical lymphoid cells. The initial differential diagnosis on bone marrow trephine biopsy sections included viral infection and peripheral T-cell lymphoma unspecified. But a cytogenetic study on bone marrow cells indicated a novel complex translocation, t(2;5;3)(p23;q35;p21), which led to confirmation of anaplastic lymphoma kinase (ALK)-positive pleomorphic small to medium-sized cells scattered in bone marrow cells, on immunohistochemistry. ALK was distributed in both nuclear and cytoplasmic regions of neoplastic cells. The patient achieved complete remission after four courses of combination chemotherapy, and received autologous peripheral stem cell transplantation (auto-PBSCT) after two additional courses of combination chemotherapy, but relapsed 2 months after auto-PBSCT in the bilateral lung. Allogeneic stem cell transplantation led to a second remission. This case demonstrates the diagnostic importance of cytogenetic study for malignant lymphoma involving bone marrow. [ABSTRACT FROM AUTHOR]

Anaplastic large cell lymphoma (ALCL) is an aggressive neoplasm of T- or null cell phenotype and is recognized as a distinct clinicopathologic subtype of non-Hodgkin lymphoma (NHL) in the revised World Health Organization (WHO) classification of hematopoietic neoplasms. It is rarely associated with leukemic phase. Most cases with leukemic involvement are the small cell variant of ALCL. These cases often lack the pleomorphism seen in the common variant of ALCL and may be misdiagnosed. We report a series of three patients who presented with leukemic phase ALCL. The patients included an 11-year-old boy, a 29-year-old man, and a 59-year-old woman. The clinical and pathologic features of these cases are reviewed. The patients in our case series with leukemic phase ALCL exhibited rare clinical features. The patients presented with massive extranodal disease involving cerebrospinal fluid (CSF), liver, spleen, lungs, and bone marrow. CSF involvement was documented morphologically as well as by flow cytometry in two patients. Two of the patients had small cell variant and the third patient had common type ALCL. The neoplastic cells in all three patients were ALK positive; however these patients died within months of diagnosis. Leukemic phase ALCL is rare, and behaves in an aggressive manner. Some, but not all, cases in the literature presenting with peripheral blood involvement had small cell variant ALCL, as seen in two of our cases. The leukemic phase of ALCL should be considered when a T-cell leukemia with unusual morphologic features is encountered. [ABSTRACT FROM AUTHOR]

Anaplastic large cell lymphoma (ALCL) is a subcategory of the mature T-cell neoplasm characterized by sheets of cluster of differentiation (CD)30-positive pleomorphic large cells mostly present as lymphadenopathy. Here, we describe a case of Small cell variant ALCL with leukemic presentation without lymphadenopathy. A 68-year-old male presented with fatigue and weakness; examination revealed a total leukocyte count of 295,000/uL. The peripheral smear showed cells having cerebriform nuclei comprising 90% of the leukocytes. The flow cytometry showed that the cells were immunopositive for CD3 (weak), CD4, CD7, and negative for the rest of the markers. The cell blocks from the peripheral blood showed cells with immunopositivity for CD30, anaplastic lymphoma kinase (ALK), and Epithelial membrane antigen (EMA). A diagnosis of the small cell variant of ALK-positive ALCL was made. Due to the presence of atypical pleomorphic cells without lymphadenopathy, the case has a diagnostic dilemma with differential diagnosis of Sezary syndrome, T-cell prolymphocytic leukemia, and adult T-cell leukemia/lymphoma. Karyotyping and additional immunohistochemistry help for the confirmation of the diagnosis., Competing Interests: None

We report four cases of a rare subtype of CD30-positive anaplastic large cell lymphoma (ALCL) with a predominant small cell component (small cell variant of ALCL) presenting with a leukaemic feature. Lymph node biopsy showed malignant cells of varying size with a predominant population of small to medium-sized malignant cells associated with large anaplastic cells strongly positive for CD30 and epithelial membrane antigen (EMA). Both large and small cells were reactive with antibody ALK1, which recognizes the chimaeric NPM-ALK protein associated with the t(2;5)(p23;q35). All patients presented with hyperleucocytosis with atypical small lymphocytes. Bone marrow involvement was detected on both aspirate and bone marrow trephine where scattered malignant cells were only demonstrated by immunostaining for CD30 and ALK protein. Atypical cells in peripheral blood, lymph node and skin biopsies showed a T or null cell phenotype. Cytogenetic analysis of blood, bone marrow and/or lymph node revealed the t(2;5)(p23;q35) characteristic of ALCL. The patients responded to chemotherapy but showed early relapse without abnormal cells in peripheral blood. This report shows that the small cell variant of ALCL may have a leukaemic presentation with peripheral blood involvement by atypical lymphocytes and provides evidence that, in the small cell variant of ALCL, the small cell component is a part of the malignant clone. [ABSTRACT FROM AUTHOR]

Anaplastic lymphoma kinase positive, anaplastic large cell lymphoma (ALCL) is an uncommon T-cell non-Hodgkin lymphoma. A rare morphological variant-small cell variant of ALCL may pose diagnostic challenge especially when it presents primarily as a soft tissue mass. We present a rare case of small cell variant of ALCL in a 14-year-old female presented with arm swelling with emphasis on clinical, morphological and immunohistochemical aspects. Pathologists should be aware of this entity when considering a differential diagnosis of malignant round cell tumor as early and correct diagnosis has important clinical implications. [ABSTRACT FROM AUTHOR]

Coxiella burnetii , the etiological agent of Q fever, undergoes a unique biphasic developmental cycle where bacteria transition from a replicating (exponential-phase) large cell variant (LCV) form to a nonreplicating (stationary-phase) small cell variant (SCV) form. The alternative sigma factor RpoS is an essential regulator of stress responses and stationary-phase physiology in several bacterial species, including Legionella pneumophila , which has a developmental cycle superficially similar to that of C. burnetii Here, we used a C. burnetii Δ rpoS mutant to define the role of RpoS in intracellular growth and SCV development. Growth yields following infection of Vero epithelial cells or THP-1 macrophage-like cells with the rpoS mutant in the SCV form, but not the LCV form, were significantly lower than that of wild-type bacteria. RNA sequencing and whole-cell mass spectrometry of the C. burnetii Δ rpoS mutant revealed that a substantial portion of the C. burnetii genome is regulated by RpoS during SCV development. Regulated genes include those involved in stress responses, arginine transport, peptidoglycan remodeling, and synthesis of the SCV-specific protein ScvA. Genes comprising the dot/icm locus, responsible for production of the Dot/Icm type 4B secretion system, were also dysregulated in the rpoS mutant. These data were corroborated with independent assays demonstrating that the C. burnetii Δ rpoS strain has increased sensitivity to hydrogen peroxide and carbenicillin and a thinner cell wall/outer membrane complex. Collectively, these results demonstrate that RpoS is an important regulator of genes involved in C. burnetii SCV development and intracellular growth. IMPORTANCE The Q fever bacterium Coxiella burnetii has spore-like environmental stability, a characteristic that contributes to its designation as a potential bioweapon. Stability is likely conferred by a highly resistant, small cell variant (SCV) stationary-phase form that arises during a biphasic developmental cycle. Here, we define the role of the alternative sigma factor RpoS in regulating genes associated with SCV development. Genes involved in stress responses, amino acid transport, cell wall remodeling, and type 4B effector secretion were dysregulated in the rpoS mutant. Cellular impairments included defects in intracellular growth, cell wall structure, and resistance to oxidants. These results support RpoS as a central regulator of the Coxiella developmental cycle and identify developmentally regulated genes involved in morphological differentiation., (Copyright © 2019 American Society for Microbiology.)

Background: Many gram-negative bacteria produce an outer membrane phospholipase A (PldA) that plays an important role in outer membrane function and is associated with virulence. Results: In the current study, we characterized a pldA mutant of Coxiella burnetii, an intracellular gram-negative pathogen and the agent of human Q fever. The C. burnetti pldA open reading frame directs synthesis of a protein with conserved PldA active site residues. A C. burnetii ΔpldA deletion mutant had a significant growth defect in THP-1 macrophages, but not axenic medium, that was rescued by complementation. Thin layer chromatography was employed to assess whether pldA plays a role in remodeling membrane lipids during C. burnetii morphological differentiation. Extracted lipids were analyzed from replicating, logarithmic phase large cell variants (LCVs), non-replicating, stationary phase small cell variants (SCVs), and a mixture of LCVs and SCVs. Similar to Escherichia coli, all three forms contained cardiolipin (CL), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). However, PE and PG were present in lower quantities in the SCV while three additional lipid species were present in higher quantities. Co-migration with standards tentatively identified two of the three SCV-enriched lipids as lyso-phosphatidylethanolamine, a breakdown product of PE, and free fatty acids, which are generally toxic to bacteria. Developmental form lipid modifications required the activity of PldA. Conclusions: Collectively, these results indicate developmentally-regulated lipid synthesis by C. burnetii contributes to colonization of macrophages and may contribute to the environmental stability and the distinct biological properties of the SCV. [ABSTRACT FROM AUTHOR]