Pancytopenia related to acquired sea-blue histiocytosis during chronic parenteral nutrition

Bone marrow smear showing histiocytes (black arrow) containing sea blue granules stained with May-Grünwald Giemsa.

Macrophage plasticity and function in cancer and pregnancy

As the soil of life, the composition and shaping process of the immune microenvironment of the uterus is worth exploring. Macrophages, indispensable constituents of the innate immune system, are essential mediators of inflammation and tissue remodeling as well. Recent insights into the heterogeneity of macrophage subpopulations have renewed interest in their functional diversity in both physiological and pathological settings. Macrophages display remarkable plasticity and switch from one phenotype to another. Intrinsic plasticity enables tissue macrophages to perform a variety of functions in response to changing tissue contexts, such as cancer and pregnancy. The remarkable diversity and plasticity make macrophages particularly intriguing cells given their dichotomous role in either attacking or protecting tumors and semi-allogeneic fetuses, which of both are characterized functionally by immunomodulation and neovascularization. Here, we reviewed and compared novel perspectives on macrophage biology of these two settings, including origin, phenotype, differentiation, and essential roles in corresponding microenvironments, as informed by recent studies on the heterogeneity of macrophage identity and function, as well as their mechanisms that might offer opportunities for new therapeutic strategies on malignancy and pregnancy complications.

The changing landscape of pediatric histiocytoses: Birth, life, and transdifferentiation of pediatric histiocytes

Histiocytic neoplasms in the children are very rare, and histiocytoses can occur in the perinatal period. The presumed origins and presentation of specific histiocytoses in the pediatric age group are described. Common and newly described histiocytoses are presented including Langerhans cell histiocytosis, Rosai-Dorfman disease, histiocytic sarcoma, ALK positive histiocytosis, and hemophagocytic lymphohistiocytosis. Molecular findings common to pediatric histiocytoses are also discussed.

Macrophage heterogeneity in the single-cell era: facts and artifacts

In this spotlight, we review technical issues that compromise single-cell analysis of tissue macrophages, including limited and unrepresentative yields, fragmentation and generation of remnants, and activation during tissue disaggregation. These issues may lead to a misleading definition of subpopulations of macrophages and the expression of macrophage-specific transcripts by unrelated cells. Recognition of the technical limitations of single-cell approaches is required in order to map the full spectrum of tissue-resident macrophage heterogeneity and assess its biological significance.

Metabolic heterogeneity of tissue-resident macrophages in homeostasis and during helminth infection

Tissue-resident macrophage populations constitute a mosaic of phenotypes, yet how their metabolic states link to the range of phenotypes and functions in vivo is still poorly defined. Here, using high-dimensional spectral flow cytometry, we observe distinct metabolic profiles between different organs and functionally link acetyl CoA carboxylase activity to efferocytotic capacity. Additionally, differences in metabolism are evident within populations from a specific site, corresponding to relative stages of macrophage maturity. Immune perturbation with intestinal helminth infection increases alternative activation and metabolic rewiring of monocyte-derived macrophage populations, while resident TIM4+ intestinal macrophages remain immunologically and metabolically hyporesponsive. Similar metabolic signatures in alternatively-activated macrophages are seen from different tissues using additional helminth models, but to different magnitudes, indicating further tissue-specific contributions to metabolic states. Thus, our high-dimensional, flow-based metabolic analyses indicates complex metabolic heterogeneity and dynamics of tissue-resident macrophage populations at homeostasis and during helminth infection.

Notch and retinoic acid signals regulate macrophage formation from endocardium downstream of Nkx2-5

Hematopoietic progenitors are enriched in the endocardial cushion and contribute, in a Nkx2-5-dependent manner, to tissue macrophages required for the remodeling of cardiac valves and septa. However, little is known about the molecular mechanism of endocardial-hematopoietic transition. In the current study, we identified the regulatory network of endocardial hematopoiesis. Signal network analysis from scRNA-seq datasets revealed that genes in Notch and retinoic acid (RA) signaling are significantly downregulated in Nkx2-5-null endocardial cells. In vivo and ex vivo analyses validate that the Nkx2-5-Notch axis is essential for the generation of both hemogenic and cushion endocardial cells, and the suppression of RA signaling via Dhrs3 expression plays important roles in further differentiation into macrophages. Genetic ablation study revealed that these macrophages are essential in cardiac valve remodeling. In summary, the study demonstrates that the Nkx2-5/Notch/RA signaling plays a pivotal role in macrophage differentiation from hematopoietic progenitors.

The evaluation of IgG4 and IgG expression in cutaneous Rosai-Dorfman disease

OBJECTIVE

The authors investigated the expression of IgG4 and IgG in cutaneous Rosai-Dorfman Disease (CRDD) to further improve the understanding of this disease.

METHODS

The authors retrospectively reviewed the clinicopathological features of 23 CRDD patients. The authors diagnosed CRDD by the presence of emperipolesis and immunohistochemical (IHC) staining of histiocytes consisting of S-100(+)/CD68(+)/CD1a(-) cells. The expressions of IgG and IgG4 in cutaneous specimens were assessed by IHC (EnVision) and quantitatively calculated by a medical image analysis system.

RESULTS

All 23 patients, including 14 males and 9 females, were confirmed to have CRDD. Their ages ranged from 17 to 68 years (mean 47.91 ± 14.16). The most frequently affected skin regions were the face, followed by the trunk, ears, neck, limbs, and genitals. In 16 of these cases, the disease presented as a single lesion. IHC staining of sections showed that IgG was positive (≥ 10 cells/High-Power Field [HPF]) in 22 cases, while IgG4 was positive (≥ 10 cells/HPF) in 18 cases. Moreover, the IgG4/IgG proportion ranged from 1.7% to 85.7% (mean 29.50 ± 24.67%, median 18.4%) in the 18 cases.

STUDY LIMITATIONS

In the majority of studies, as well as in the current study, the design. RDD is a rare disease, so the sample size is small. In the next studies to come, the authors will expand the sample for multi-center verification and in-depth study.

CONCLUSION

The positive rates of IgG4 and IgG and the IgG4/IgG ratio assessed through IHC staining may be important in understanding the pathogenesis of CRDD.

Top Ten Lymphoproliferative Lesions Not to Miss When Evaluating Oral Ulcer Biopsies

BACKGROUND

Oral ulcers represent a full thickness loss of the mucosal epithelium leading to exposure of the submucosal connective tissue. These are common and usually self-limited lesions, although they may sometimes result from neoplasms, most commonly squamous cell carcinoma. Lymphoproliferative disorders may be difficult to diagnose in apthous ulcers since they mimic reactive inflammation.

METHODS

This review presents ten rare oral lymphoid proliferations which should not be missed when assessing oral ulcer biopsies.

RESULTS

The ten lesions include several with diagnostic cells which look similar to the histiocytes of a reactive inflammatory ulcer, including Rosai-Dorfman disease, reticulohistiocytoma, Langerhans cell histiocytosis, and traumatic ulcerative granuloma. Other lesions, such as EBV-positive mucocutaneous ulcer, extranodal marginal zone lymphoma of mucosal-associated lymphoid tissue, and plasmablastic lymphoma have lymphoid and/or plasma cell differentiation that mimic the reactive lymphocytes and plasma cells found in reactive ulcers. Two dendritic cell lesions, follicular dendritic cell sarcoma and blastic plasmacytoid dendritic cell neoplasm, both have distinct phenotypes which are required to make an accurate diagnosis.

CONCLUSION

Each of these lesions are diagnosed by evaluating their histology, along with their phenotypic profile, which is sometimes enhanced by pertinent molecular findings.

[Rare differential diagnosis in bilateral gonalgia]

We report on a 47-year-old patient suffering from bilateral gonalgia, weight loss and night sweats without fever of several months' duration. Diagnostic work-up for infectious and autoimmune diseases showed no abnormal results. A CT scan showed extensive foci of sclerosis throughout the axial skeleton. In the trephine biopsy, foamy cell infiltrates were found with expression of histiocytic markers without expression of Langerhans cell markers. Molecular analysis revealed a low allelic BRAF V600E and BCOR mutation. The diagnosis of Erdheim-Chester disease (ECD) was made. The histologic findings and molecular findings, the clinical and radiologic presentation before and 6 months after therapy as well as possible differential diagnoses of this very rare disease are discussed.

An improved organotypic cell culture system to study tissue-resident macrophages ex vivo

Tissue-resident macrophages (TRMs) perform organ-specific functions that are dependent on factors such as hematopoietic origin, local environment, and biological influences. A diverse range of in vitro culture systems have been developed to decipher TRM functions, including bone marrow-derived macrophages (BMDMs), induced pluripotent stem cell (iPSC)-derived TRMs, or immortalized cell lines. However, despite the usefulness of such systems, there are notable limitations. Attempts to culture primary macrophages often require purification of cells and lack a high cell yield and consistent phenotype. Here, we aimed to address these limitations by establishing an organotypic primary cell culture protocol. We obtained long-term monocultures of macrophages derived from distinct organs without prior purification using specific growth factors and tissue normoxic conditions that largely conserved a TRM-like identity in vitro. Thus, this organotypic system offers an ideal screening platform for primary macrophages from different organs that can be used for a wide range of assays and readouts.

Histiocytic and dendritic cell neoplasms

BACKGROUND

Histiocytic and dendritic cell neoplasms (HDCNs) represent very rare tumors, which have been the subject of debate during the last few years.

OBJECTIVES

We aimed to provide a comprehensive review of the subject.

MATERIALS AND METHODS

The experience gained by the authors in large international studies and as a national reference center has been summarized to highlight the characteristics of each entity.

RESULTS

The clinical, morphologic, phenotypic, and molecular data of the different entities included under the heading of HDCNs are extensively discussed.

CONCLUSION

Currently, HDCNs are classified in the group of orphan diseases for which a standardized therapy is lacking. An international registry would facilitate expansion and dissemination of knowledge of these diseases and improve their treatment.

Unusual primary central nervous system T-cell/histiocyte-rich large B-cell lymphoma: a case report

We report the case of a 54-year-old immunocompetent woman who presented with a primary T-cell/histiocyte-rich large B-cell lymphoma (TCHRLBCL) of the central nervous system without systemic involvement, diagnosed by means of a brain biopsy. She was treated with corticosteroids and we subsequently started chemotherapy with rituximab, methotrexate, ifosfamide and intrathecal cytarabine. The patient's symptoms gradually improved over the first weeks and we followed-up with autologous haematopoietic cell transplantation. The patient has been in complete remission for a year. Primary TCHRLBCL of the central nervous system in an immunocompetent patient is an extremely rare condition that requires a multidisciplinary approach. This case highlights the importance of undergoing a sequential work-up and establishing a treatment despite the absence of evidence-based guidelines.

Paraneoplastic Granuloma Annulare Associated with Metastatic Lung Cancer

A 60-year-old Caucasian woman with a 15-year smoking history presented with new, asymptomatic, pink lesions that gradually appeared over a period of 6 weeks. Physical examination revealed erythematous annular and nummular plaques on her upper and lower extremities, chest, and abdomen (Figure 1A and 1B). A shave biopsy from the right thigh revealed focal areas of necrobiotic collagen in the superficial portion of the dermis, surrounded by histiocytes, multinucleated giant cells, and lymphocytes, consistent with granuloma annulare (GA) (Figure 2).¹.

Post-Chemotherapy Histiocyte-Rich Pseudotumors: Radiologic and Endoscopic Mimics of Residual Lymphoma

Development of post-chemotherapy histiocyte-rich pseudotumor (PHP) is an underrecognized event following therapy in lymphoma patients and may mimic residual tumor using current therapy monitoring protocols. We report a series of 5 patients with PHP along with a review of the literature. In our series, we describe 3 patients with persistent hypermetabolic masses by positron emission tomography-computed tomography, one with persistent terminal ileal nodules on endoscopy, and one with bone marrow involvement, a site not associated with mass-like disease. Twenty-three patients with long-term follow-up were identified from our series and review of the literature. Forty-four percent of patients received additional therapy, and only 4% of patients died of lymphoma. This study illustrates that PHPs are not identified using current lymphoma therapy monitoring algorithms and may result in overtreatment with risk for additional therapy-related complications. The need for confirmatory tissue biopsy in this setting is recommended.

[A toddler with yellow nodules]

A 1.5 year-old boy is diagnosed with juvenile xanthogranuloma. Juvenile xanthogranuloma is a benign proliferation of histiocytes, which is generally self-limiting. Extracutaneous manifestations are rare and mostly seen in case of multiple lesions and/or localisation around eyes. Routine additional examination is not indicated.

[Rosai-Dorfman disease as a rare cause of a pancreatic mass]

The CT and MRI scans of a 70-year-old male patient revealed a mass in the pancreatic head and a 2.8-cm peripancreatic lymph node. Under steroid therapy the mass did not show regression. Finally, a pancreatoduodenectomy was performed. Histologically, Rosai-Dorfman disease (RDD) was diagnosed. RDD is a rare histiocytic disorder with usually nodal but sometimes also extranodal involvement. Herein we report a rare case of extranodal RDD with intrapancreatic localization.

Histiocytoses and neoplasms of the macrophage-dendritic cell lineages. Comparison of recent WHO classification published 2017 and classification of Histiocyte Society published 2016

The histiocytoses are rare disorders characterized by the accumulation of cells thought to be derived from dendritic cells or macrophages. Their clinical behaviour ranges from mild to disseminated and, sometimes, life-threatening forms. The incidence of this diseases is much smaller, then the incidence of diseases derived from lymphocytic or myeloid lineage. Langerhans cell histiocytosis is most frequent disease from this group. The last version of WHO classification from 2017 and last version of classification published by Histiocyte Society is summarised in this paper.

A case of unusual histiocytic colitis in a chronic alcoholic obese patient with ankylosing spondylitis

A 64 year-old Caucasian man was first investigated 21 years ago for persistent diarrhoea. A colonoscopy revealed an erosive pancolitis with unusual vacuolated macrophages. Characteristics of ulcerative colitis or Crohn's disease were absent. Similar findings were observed consistently over the following years. A treatment with Sulfasalazine, Methotrexate or Budesonide was efficient. Histiocytic colitis is rare, and the various causes and different diagnoses are reviewed. The cause for the chronic pancolitis in this obese chronic alcoholic remains unknown at the time of writing. Links to the dyslipidaemia and chronic ankylosing spondylitis presented by the patient are possible hypotheses worth investigating further.

[Eosinophilic granuloma of the parietal bone of an adult patient with BRAF mutation]

The paper describes a case of eosinophilic granuloma of the parietal bone in a 32-year-old man. Histological examination revealed a large number of bean-shaped Langerhans cell histiocytes with lobed nuclei and nuclear grooves. The histiocytes alternated with the foci of obvious eosinophilic infiltration and with eosinophilic microabscesses. There were osteoclast-like multinucleated giant cells, bone resorption, and numerous bone rods covered with osteoblast chains. The histiocytes expressed CD1α, langerin, CD68, S100, and p53 (in 90.0% of the tumor cells). The Ki-67 proliferation index was 18.0%. A molecular genetic study identified BRAFV600E mutation (nucleotide substitution s.1799 T>A (p.V600E) in the heterozygous state). Clinical and morphological data and the results of molecular genetic studies led to the conclusion that there was eosinophilic granuloma of the right parietal bone (the unifocal form of Langerhans cell histiocytosis (LCH), type I, group A1, with the monoossal nature of lesion and with BRAFV600E mutation). In adults, this disease is extremely rare (2-5 cases of LCH per million people, bone loss in the fourth decade of life in 2.5% of the patients).

Wade's histoid leprosy: three clinical presentations

Wade's histoid leprosy is a rare form of multibacillary leprosy with distinctive characteristics which were first described in patients treated with a short course of sulfones. Wade's histoid leprosy may occur as a relapse, in the setting of sulfone resistance, or may present de novo. We report the clinical, histologic, immunologic, and bacteriologic features of three adult male patients with this rare variant of lepromatous leprosy as the initial presentation of the disease, observed in the Dermatology Department of Hospital Córdoba, Córdoba, Argentina between 1999 and 2003. Two of the three patients were from an endemic leprosy area. All patients presented with a number of erythematous to brownish gray, firm but elastic nodules involving mainly the extremities, which responded to treatment for multibacillary leprosy without reactional episodes.

Orbital involvement in Erdheim-Chester disease

Erdheim-Chester disease is a rare, idiopathic, non-Langerhans' cell, histiocytic disorder. To our knowledge this is only the second case of Erdheim-Chester disease reported in the Chinese population. We describe a 45-year-old woman presenting with unilateral proptosis and periorbital xanthelasma. Histopathological examination revealed a xanthogranulomatous lesion expressing CD68, but negative for S100 protein, CD1a, CD3, or CD20. Systemic involvement was evident on bone scanning, and involvement of the thorax and abdominal aorta was seen on computed tomography. Despite treatment with systemic steroids, immunosuppressants, chemotherapy and interferon, progressive deterioration occurred. Our patient's clinical course was consistent with reports in the literature. Unfortunately, our patient developed neutropenic fever and died from septicaemic shock. Although Erdheim-Chester disease is a rare entity, especially in the Chinese population, an unusual presentation with orbital masses and bilateral xanthelasma, associated with systemic features, should raise the suspicion of this serious and potentially fatal disease.

Malacoplakia of the cranium and cerebrum in a human immunodeficiency virus-infected man. Case report

Malacoplakia is a rare chronic inflammatory disease associated with infection and immunosuppression, and very few occurrences have been reported in the cerebrum. The authors describe the case of a 41-year-old man with advanced human immunodeficiency virus (HIV) infection who presented with a very aggressive malacoplakia lesion that had extended through the scalp, temporalis muscle, skull bone, and deep through the dura mater into the superior sagittal sinus and adjacent brain. Pathological examination revealed sheets of histiocytes invading these structures, and macrophages containing numerous round bodies known as Michaelis-Guttmann bodies, pathognomic for malacoplakia. Because of the rarity of this phenomenon, appropriate treatment and management of malacoplakia are speculative. A complete resection of the lesion, antibiotic therapy, and treatment of his underlying HIV infection had a salutary effect, with the patient faring well more than 9 months postoperatively.

[Hormonal and progenotoxic properties of mammary fat in pre- and postmenopausal cancer patients]

Since breast cancer may emerge both before and after menopause onset, relevant forms of the disease show marked biological and clinical differences. Intrinsic properties of mammary fat located in the vicinity of tumor, which play a definitive role in stromal-epithelial interactions, are an important factor of development of such differences. The DNA damage promoting hormonal (leptin and adiponectin production, aromatase activity) and progenotoxic. The properties of mammary fat such as formation of tumor necrosis factor, interleukin-6, nitric oxide, malonic aldehyde, macrophage/histiocyte infiltration and estrogen 4-hydroxylase expression, were studied in mammary fat tissue of 95 patients with receptor-positive or receptor-negative breast tumors (reproductive--25, menopausal--70). It was found that progenotoxic properties might somewhat predominate, as far as differences in parameters and pathways are concerned, both in menopausal and still cycling patients. Hence, progenotoxic damage which represents mammary fat tissue status is perhaps modified by a number of genetic and mitochondrial factors. It may exert unfavorable effect on the course of the disease within a fairly wide period.

T-Cell/Histiocyte-Rich Large B-Cell Lymphoma Displays a Heterogeneity Similar to Diffuse Large B-Cell Lymphoma

T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL), a proliferating peripheral B-cell neoplasm, is a morphologic variant of diffuse large B-cell lymphoma (DLBCL), which may be confused with Hodgkin's lymphoma, non-Hodgkin's lymphoma, and reactive lymphadenopathies. Though more recent studies suggested that it might be a distinct clinicopathologic entity and/or a heterogeneous entity with derivation from germinal center B cells, its histogenetic derivation remains controversial. The authors analyzed 30 cases of THRLBCL to further characterize the origin of the neoplastic cells using immunohistochemical and molecular studies for expression of Bcl-6, CD10, and CD138, as well as rearrangements of IgH/bcl-2 genes on paraffin-embedded tissue. Half of the cases (15/30) showed Bcl-6 expression and five cases (19%) showed CD10 expression, but none had CD138 expression (0/20). Only three cases showed coexpression of both Bcl-6 and CD10. Molecular studies performed in 21 cases detected rearrangement of immunoglobulin heavy gene in 18 cases, with none having detectable Bcl-2 gene rearrangement. These data indicate that similar to DLBCL, the cell origin of neoplastic cells in THRLBCL is composed of a heterogeneous group of proliferating peripheral B cells, with only some cases originating from germinal center B cells and others derived from heterogeneous origins. Lack of Bcl-2 gene rearrangements seems to argue against a possible progression from preexisting follicular lymphoma. Thus, the normal counterpart of the neoplastic cells cannot at this time be the sole basis for the subclassification of THRLBCL.

Primary gastric histiocytic sarcoma in a dog--a case report

A 12-year-old intact female mixed breed dog was presented for chronic, intermittent vomiting and diarrhoea. On endoscopic examination a protruding mass arising from the mucosal surface of the pyloric region was detected. Cytological and histological examination revealed an accumulation of pleomorphic round/oval phagocytic cells suggesting histiocytic origin. This was confirmed by immunohistochemistry. No extra-gastric involvement was detected on clinical examination or at necropsy. This is the first report of primary gastric histiocytic sarcoma in a dog.

[The RT-PCR-identified Fas and FasL expression and apoptosis in mouse hepatoma MH-22a and histiocytic sarcoma J-774 clonal lines coupled with in vitro cultivation with syngenic splenocytes]

Malignant growth is associated with various patterns of interaction between tumor cells and those of the body immune system, interaction between Fas-receptor (Fas) and Fas-ligand (FasL) expression being one of them. These mechanisms were simulated in vitro using the main cell populations from murine hepatoma MH-22a, histiocytic sarcoma J-774 and their clonal lines obtained from cocultivation of tumor cells and syngenic splenocytes. Fas and FasL expression was identified by the RT-PCR method while apoptosis--by electrophoresis of low molecular DNA fractions and clonogenic survival.

Antibiotic-responsive histiocytic ulcerative colitis in 9 dogs

Canine histiocytic ulcerative colitis (HUC) is characterized by colonic inflammation with predominantly periodic acid-Schiff (PAS)-positive macrophages. The inflammation results in colonic thickening, ulcerations, and distortion of normal glandular architecture. Resultant clinical signs consist of chronic large bowel diarrhea, tenesmus, and marked weight loss, and the disease frequently results in euthanasia. Conventional therapy consists of some combination of prednisone, azathioprine, sulfasalazine, and metronidazole. Nine dogs (8 Boxers and 1 English Bulldog) with histologic confirmation of HUC were treated with antibiotic therapy (either with enrofloxacin alone or in combination with metronidazole and amoxicillin). Clinical signs, physical examination findings, laboratory abnormalities, and the histologic severity of the disease were evaluated. Four of the 9 dogs had been treated previously with conventional therapy and had failed to respond favorably; then, these dogs were placed on antibiotic therapy (enrofloxacin, n = 1; enrofloxacin, metronidazole, and amoxicillin, n = 3) and had resolution of clinical signs within 3-12 days. Five dogs were treated solely with antibiotic therapy (enrofloxacin, n = 1; enrofloxacin and metronidazole, n = 1; enrofloxacin, metronidazole, and amoxicillin, n = 3), and clinical signs resolved in 2-7 days. Repeated biopsy specimens were obtained from 5 dogs after treatment, and all showed marked histologic improvement. The increase in body weight after treatment was statistically significant (P = .01). Three dogs currently are not on any treatment and have had resolution of clinical signs for up to 14 months. These observations suggest that an infectious agent responsive to antibiotics plays an integral role in the clinical manifestation of canine HUC, and they support the use of antibiotics in its treatment.

A lipolytic enzyme in reactive histiocytes of guinea pigs with experimental encephalomyelitis

A lipolytic enzyme has been demonstrated by means of a cytochemical technique and by direct chemical assay in granulomatous tissues of guinea pigs with encephalomyelitis and demyelinization resulting from the injection of an emulsion comprised of brain tissue and adjuvants, including Mycobacterium butyricum. Combined histologic and cytochemical studies showed that the lipolytic enzyme was present in the cytoplasm of a large proportion of the reactive histiocytes in the granulomatous tissue around the site of injection in the diseased animals, and that the enzyme-containing histiocytes were even more numerous in the inflamed regional lymph nodes. In control experiments, when emulsions lacking either brain tissue or M. butyricum were injected in previously normal guinea pigs, the experimental condition did not develop; under these circumstances the lipolytic enzyme was found in only a small proportion of the cells of the granulomatous tissue around the injection sites, and it was almost negligible in the regional lymph nodes of these animals. It was absent from the cells of the lymph nodes of normal animals, and from the cells of talcum and aluminum hydroxide granulomas produced experimentally in guinea pigs. The lipolytic enzyme may be a factor in the pathogenesis of the experimental encephalomyelitis and demyelinization.

Inflammatory myopathy with abundant macrophages (IMAM): a condition sharing similarities with cytophagic histiocytic panniculitis and distinct from macrophagic myofasciitis

We describe the unreported pattern of inflammatory myopathy with abundant macrophages (IMAM) as a main differential diagnosis of postimmunization aluminum hydroxide-induced macrophagic myofasciitis (MMF). IMAM was mainly detected among patients with a dermatomyositis (DM)-like disease. Among 113 muscle biopsies from DM patients collected from 1974 to 2000, intensity of macrophage infiltration was highly variable: 41.5% (-/+); 34.5% (+); 17% (++): and 7% (+++). The 27 patients from groups (++) and (+++) had a similar pattern of macrophagic infiltration and were considered to have IMAM. They were compared to 40 MMF patients. In IMAM, macrophage infiltrates were diffuse and correlated positively with both T cell infiltrates and acute muscle fiber damage, and showed pictures of hemophagocytosis (21/27). Connective tissue structures were infiltrated by noncohesive, ribbon-forming collections of large basophilic macrophages containing no crystalline inclusions. In MMF, macrophage infiltrates were focal and formed compact well-delineated aggregates of granular PAS+ cells, loaded with crystalline aluminum hydroxide particles, in the absence of either hemophagocytosis or conspicuous muscle damage. Review of the literature indicates similarities between IMAM and "cytophagic histiocytic panniculitis" (CHP), a condition characterized by T cell-triggered macrophage hyperactivation. Both IMAM and CHP, but not MMF, may be associated with a life-threatening hemophagocytic syndrome.