Xanthoma typically occurs in the subcutaneous tissues, with rare cases of xanthoma in the joints. However, the case of knee joint osteonecrosis combined with xanthoma is even more uncommon. In this article, we described a 50-year-old female patient who suffered xanthoma in the knee joint on the basis of osteonecrosis of the knee joint. The primary clinical symptoms were knee joint pain and limited mobility. The patient initially received conventional treatment for osteonecrosis. However, there was no significant improvement. Later, we found a synovial xanthoma in the patient\'s knee. Finally, she underwent arthroscopic excision of the knee joint synovial xanthoma. Following the procedure, her VAS score decreased from 7 to 2, and knee joint mobility increased from 10-103° to 10-140°. Through our follow-up, the patient did not exhibit symptom recurrence. This case is valuable as it provides a feasible therapeutic approach for future clinical applications.

A xanthoma is an extremely rare condition that affects the soft tissues and bones and is characterized by a predominance of lipid-rich foamy histiocytes. The onset of xanthomas is frequently accompanied by primary or secondary hyperlipidemia. Primary bone xanthomas are very uncommon benign bone lesions that are not linked to hyperlipidemia. Histopathologically, they are distinguished by histiocytes, an abundance of foam cells or xanthoma cells that contain lipids, and a paucity of multinucleated giant cells. There have only been four reports of primary maxillary xanthoma in the medical literature. We present a rare primary intrabony xanthoma of the anterior maxilla in a 23-year-old normolipidemic female patient with solitary radiolucency. Using CD68, S-100, and CD1a immunohistochemical staining, it is possible to distinguish between macrophage/non-Langerhans histiocytes and Langerhans histiocytes. Therefore, a diagnosis of a central xanthoma of the jaws must be made.

UNASSIGNED: Xanthomas are skin swellings that are caused by the accumulation of cholesterol and lipids in the body. They are associated with lipid disorders, such as familial hypercholesterolemia (FH). FH is a rare genetic disorder, which is characterized mainly by high levels of low density lipoprotein cholesterol.
UNASSIGNED: The authors report a case of an 11-year-old female who had multiple swellings all over the body with the largest measuring 7×4×3 cm in diameter. These lesions were gradually increasing in size since 4 years. She was being bullied by her school colleagues because of swellings appearance. Clinical examination revealed multiple yellowish masses on the patient\'s elbows, knees, and buttocks which were painless, firm, and nontender. Laboratory tests revealed elevated levels of serum cholesterol (512 mg/dl) and low density lipoprotein cholesterol (469.2 mg/dl). Masses ultrasound showed similar echogenicity to upper and lower extremities subcutaneous fat. Incisional biopsy microscopic images revealed clusters of foam cells. These findings led to a diagnosis of Homozygous FH and she underwent surgery to remove the xanthomas on her elbows.
UNASSIGNED: Xanthomas are small, yellowish skin swellings that form due to the presence of high lipids. As they are typically painless and small, this could lead to a late treatment or misdiagnosis. Drugs, lifestyle changes, and surgery represent treatment plan options.
UNASSIGNED: Xanthomas can be the first indication of an underlying hypercholesterolemia problem and this case report highlights the importance of early diagnosis of Homozygous FH by providing the suitable management for this case in its early stages which can prevent developing serious complication.

BACKGROUND: Sitosterolemia, an autosomal recessive condition, is characterized by impaired metabolism of plant sterols. Clinical symptoms include skin xanthoma, premature atherosclerotic disease, arthritis, and unexplained hematological abnormalities. However, there is a dearth of studies on sitosterolemia-related brain damage.
METHODS: This study focused on the family of two sitosterolemia patients who presented with severe hypercholesterolemia and xanthoma. Radiological examinations, biopsies, whole-exome sequencing (WES), and plant sterol tests were conducted.
RESULTS: The index patient, a 66-year-old female, initially exhibited weakness in both lower limbs and later developed urinary and fecal incontinence. Neuroimaging showed that the falx of the brain had irregular fusiform thickening. Significant tissue edema was observed around the lesions in the bilateral frontal-parietal lobes. Pathological analysis of the biopsied brain lesion revealed extensive cholesterol crystal deposition and lymphocyte infiltration in the matrix. The index patient who experienced cerebral impairment and her sister both carried two compound heterozygous variants in ATP binding cassette transporter G5 (ABCG5). These included the nonsense variants NM_022436: c.751 C > T (p.Q251X) in exon 6 and NM_022436: c.1336 C > T (p.R446X) in exon 10. A notable increase in plant sterol levels was observed in the younger sister of the index patient.
CONCLUSIONS: This study highlights a previously unreported neurological aspect of sitosterolemia. Imaging and pathology findings suggest that cholesterol crystals may be deposited in connective tissues such as the cerebral falx and pia mater through blood circulation.

Adipocytic tumors are mesenchymal tumors that are commonly reported in psittacine birds; however, large-scale studies evaluating their prevalence and associated risk factors are lacking. A retrospective study of adipocytic tumors in psittacine birds was performed by reviewing pathology submissions from the University of California, Davis-Drury Reavill Pathology Database, containing 26 013 submissions from psittacine birds (1998-2018). Age, sex, genus, anatomic distribution, and pathological diagnosis were collected for each case when available. The prevalence, risk factors, and association with other lipid-accumulation disorders were reported. A total of 450 cases of lipoma, 129 cases of myelolipoma, 35 cases of hemangiolipoma, 31 cases of liposarcoma, and 451 cases of xanthoma were identified. The prevalence of adipocytic tumors and xanthomas on necropsy was 1.3% (158/11 737, 95% confidence interval [CI]: 1.1-1.6). Adipocytic tumors were identified in 27 genera. Amazona (odds ratio [OR] = 1.93, 95% CI: 1.24-2.99, p = 0.004), Myiopsitta (OR = 2.3, 95% CI: 1.0-5.2, p = 0.041), Melopsittacus (OR = 3.4, 95% CI: 2.1-5.5, p < 0.001), and Agapornis (OR = 3.5, 95% CI: 2.0-6.1, p < 0.001) had significantly higher odds of developing adipocytic tumors compared with other genera, whereas Ara had significantly lower odds (OR = 0.5, 95% CI: 0.3-0.9, p = 0.030). Age was also a significant risk factor for many types of adipocytic tumors. There was no significant association between general adipocytic tumor formation and atherosclerosis or hepatic lipidosis. Xanthomas were associated with atherosclerosis (OR = 1.88, 95% CI: 1.01-3.51, p = 0.048), but not hepatic lipidosis (p = 0.503). On necropsy, the trunk and air sacs were the most common sites of xanthoma formation, whereas the trunk and liver were the most common sites of lipoma and myelolipoma formation, respectively.

BACKGROUND: Both xanthogranuloma and xanthoma clinically manifest as yellowish skin lesions. Historically, the gold standard for diagnosis was skin histopathological examination. Currently, the advent of reflectance confocal microscopy (RCM) offers additional diagnostic support for these diseases by revealing their microscopic features, thereby enhancing the theoretical foundation for diagnosis.
OBJECTIVE: This study aimed to elucidate the distinctive characteristics of RCM images in xanthogranuloma and xanthoma, assess their diagnostic value, and investigate the relationship between RCM and histopathological features, ultimately boosting diagnostic accuracy.
METHODS: RCM and histopathological examinations were conducted on 13 patients with xanthogranuloma and 12 with xanthoma, recruited from our Dermatology Clinic between August 2022 and November 2023. The study involved analyzing RCM image features and correlating them with histopathological findings.
RESULTS: The RCM images of 13 xanthogranuloma and 12 xanthoma cases showed similar features. Xanthogranuloma predominantly exhibited epidermal atrophy and thinning in 6 cases (46.15%). Additionally, in 69.23% of cases, scattered small mononuclear inflammatory cells were infiltrated in the superficial and middle dermis layers. Medium to high refractive cells, predominantly vacuolated and resembling foam, were observed in 61.54% of cases. All cases demonstrated high refractive cells with distinct target-shaped, disc-shaped, horseshoe-like, and flower-ring structures. Concordance rates with histopathological examinations were 69.23, 92.31, 92.31, and 100%, respectively. Regarding xanthoma, epidermal atrophy and thinning occurred in two cases (16.67%), and mononuclear inflammatory cell infiltration was observed in 25% of cases. High refractive cells with the previously mentioned shapes were present in 100% of cases, though only 16.67% displayed these characteristics exclusively. The concordance rates were 66.67, 91.67, 100, and 91.67%, respectively.
CONCLUSIONS: RCM imaging of xanthogranuloma and xanthoma presents distinctive, highly consistent features with their histopathology, offering valuable insights for clinicians in diagnosing and differentiating these conditions.

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BACKGROUND: Skull lesions are a common finding in children, with dermoid cysts and eosinophilic granulomas observed most frequently. However, primary intraosseous xanthomas of the calvaria, which are lytic, expansile lesions that develop without underlying hyperlipidemic disease, are rare in children, with only one prior case reported.
METHODS: The authors describe the case of a healthy 6-year-old male who presented with a 2-month history of an enlarging midline skull mass that developed after a recent minor trauma. Imaging showed a full-thickness, lytic frontal bone lesion with an aggressive appearance and heterogeneous contrast enhancement. The patient underwent gross-total resection of the lesion with placement of a mesh cranioplasty. Histopathology revealed a primary intraosseous xanthoma. The patient was discharged on postoperative day 2 and required no further treatment at the 1-month follow-up.
CONCLUSIONS: This is the first reported case of a primary intraosseous xanthoma in the frontal bone of a pediatric patient. It emphasizes the need to include primary xanthomas in the differential diagnosis for pediatric skull lesions, particularly when the lesion has an aggressive radiographic appearance or the patient has a history of focal trauma. Furthermore, our findings indicate that resection, together with subsequent monitoring for lesion reccurrence, is an adequate first-line treatment.

BACKGROUND: A xanthoma is a rare bone condition consisting of a predominant collection of lipid-rich, foamy histiocytes. The central xanthoma of the jaws is a unique benign tumor.
METHODS: A 15-year-old Caucasian male has been presented to our department. He had radiological changes in the area of the left mandibular angle, with an area of diffuse osteolysis of 3.0 cm by 2.0 cm. Computed tomography reveals an area of diffuse osteolysis that starts from the distal root of the lower second molar and reaches the ascending process. A bone biopsy was performed, which revealed a benign proliferative process composed of histiocytic cells involving and infiltrating trabecular bone in a background of loose fibrous connective tissue devoid of any other significant inflammatory infiltrate. The size of the formation was 2.9 cm by 2.0 cm. Immunohistochemical staining for CD68 was strongly positive and negative for S-100 and CD1a. From routine blood tests, cholesterol, triglycerides, and blood sugar are within normal values, which excludes systemic metabolic disease. Subsequent to the surgical intervention, the patient underwent postoperative assessments at intervals of 14, 30, 60 days, and a year later, revealing the absence of any discernible complications during the aforementioned observation periods.
CONCLUSIONS: The diagnosis of primary xanthoma of the mandible is rare and can often be confused with other histiocytic lesions. A differential diagnosis should be made with nonossifying fibroma and Langerhans cell histiocytosis, as in our case. In these cases, immunohistochemistry with CD 68, S-100, and CD1a, as well as blood parameters, are crucial for the diagnosis.

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