Incidental finding of F-18 FDG skin uptake in a patient with psoriasis during the evaluation of a recurrent papillary thyroid carcinoma

CD147 Facilitates the Pathogenesis of Psoriasis through Glycolysis and H3K9me3 Modification in Keratinocytes

Psoriasis is a chronic inflammatory skin disease featuring rapid proliferation of epidermal cells. Although elevated glycolysis flux has been reported in psoriasis, the molecular mechanisms underlying its pathogenesis remain unclear. We investigated the role of the integral membrane protein CD147 in psoriasis pathogenesis, observing its high expression in psoriatic skin lesions of humans and imiquimod (IMQ)-induced mouse models. In mouse models, genomic deletion of epidermal CD147 markedly attenuated IMQ-induced psoriatic inflammation. We found that CD147 interacted with glucose transporter 1 (Glut1). Depletion of CD147 in the epidermis blocked glucose uptake and glycolysis in vitro and in vivo. In CD147-knockout mice and keratinocytes, oxidative phosphorylation was increased in the epidermis, indicating CD147's pivotal role in glycolysis reprogramming during pathogenesis of psoriasis. Using non-targeted and targeted metabolic techniques, we found that epidermal deletion of CD147 significantly increased the production of carnitine and α-ketoglutaric acid (α-KG). Depletion of CD147 also increased transcriptional expression and activity of γ-butyrobetaine hydroxylase (γ-BBD/BBOX1), a crucial molecule for carnitine metabolism, by inhibiting histone trimethylations of H3K9. Our findings demonstrate that CD147 is critical in metabolic reprogramming through the α-KG-H3K9me3-BBOX1 axis in the pathogenesis of psoriasis, indicating that epidermal CD147 is a promising target for psoriasis treatment.

The role of 18F-FDG PET/CT in primary cutaneous lymphoma: an educational review

INTRODUCTION

Primary cutaneous lymphoma (PCL) is a cutaneous non-Hodgkin's lymphoma that originates in the skin and lacks extracutaneous spread upon initial diagnosis. The clinical management of secondary cutaneous lymphomas is different from that of PCLs, and earlier detection is associated with better prognosis. Accurate staging is necessary to determine the extent of disease and to choose the appropriate treatment. The aim of this review is to investigate the current and potential roles of ¹⁸F- fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG PET/CT) in the diagnosis, staging, and monitoring of PCLs.

METHODS

A focused review of the scientific literature was performed using inclusion criteria to filter results pertaining to human clinical studies performed between 2015 and 2021 that analyzed cutaneous PCL lesions on ¹⁸F PET/CT imaging.

RESULTS & CONCLUSION

A review of 9 clinical studies published after 2015 concluded that ¹⁸F-FDG PET/CT is highly sensitive and specific for aggressive PCLs and proved valuable for identifying extracutaneous disease. These studies found ¹⁸F-FDG PET/CT highly useful for guiding lymph node biopsy and that imaging results influenced therapeutic decision in many cases. These studies also predominantly concluded that ¹⁸F-FDG PET/CT is more sensitive than computed tomography (CT) alone for detection of subcutaneous PCL lesions. Routine revision of nonattenuation-corrected (NAC) PET images may improve the sensitivity of ¹⁸F-FDG PET/CT for detection of indolent cutaneous lesions and may expand the potential uses of ¹⁸F-FDG PET/CT in the clinic. Furthermore, calculating a global disease score from ¹⁸F-FDG PET/CT at every follow-up visit may simplify assessment of disease progression in the early clinical stages, as well as predict the prognosis of disease in patients with PCL.

Pyruvate Kinase M2 Mediates Glycolysis Contributes to Psoriasis by Promoting Keratinocyte Proliferation

Psoriasis is characterized by keratinocyte proliferation and immune cell infiltration. M2 isoform of pyruvate kinase (PKM2) was reported to have an important role in cell proliferation, which is a rate-limiting enzyme that regulates the final step of glycolysis. However, how PKM2 regulates cell metabolism and proliferation in psoriatic keratinocytes is still poorly understood. Interestingly, we found that PKM2 was highly expressed in psoriatic epidermis from patients and mouse models. PKM2 overexpression promoted keratinocyte glycolytic metabolism while knockdown inhibited keratinocyte proliferation and glycolysis. Mice lacking PKM2 specifically in keratinocytes, pharmacological inhibition of PKM2 or glycolysis inhibited keratinocyte proliferation and showed obvious remission in an imiquimod-induced psoriatic mouse model. Moreover, the inhibitor of the EGF-receptor blocked EGF-stimulated PKM2 expression and glycolysis in keratinocytes. We identify PKM2 as an upregulated gene in psoriasis. PKM2 is essential in keratinocyte over-proliferation and may represent a therapeutic target for psoriasis.

18F-FDG PET/CT in Xanthoma Disseminatum

A 64-year-old woman who had yellowish orange-colored, sharp-edged, and flat skin plaques and back pain for about a year was referred for F-FDG PET/CT imaging and her bone marrow biopsy revealed 10% to 20% atypical plasma cells suggestive of monoclonal gammopathy. PET/CT showed linear F-FDG uptake on the surface of the skin on the neck, axillary, chest, inframammary, and inguinal regions. Punch biopsy revealed numerous histiocyte infiltrates with large vacuoles, xanthomized cytoplasm in the dermis, and midsection, and there are several Touton-type giant cells supporting the preliminary diagnosis of xanthoma disseminatum.

Paclitaxel-induced dermal hypersensitivity lesions: 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography

Paclitaxel is frequently used for the treatment of patients with nonsmall cell lung cancer. Hypersensitivity reactions (HSRs) have been one of the toxicities observed with administration of paclitaxel. Here, we presented a case of a 49-year-old man with a history of right lung mass proven by biopsy to be a nonsmall cell lung cancer (squamous cell carcinoma) who developed HSR during therapy. In addition to the hypermetabolic primary malignancy, a positron emission tomography/computed tomography (PET/CT) scan showed multiple hypermetabolic skin lesions at several parts of the body. These cutaneous lesions were resolved in the restaging PET/CT scan performed after completion of the six cycles of chemotherapy. This is the first documented case of comparative PET/CT findings of a paclitaxel-induced hypersensitivity.

Assessing Cutaneous Psoriasis Activity Using FDG-PET: Nonattenuation Corrected Versus Attenuation Corrected PET Images

Psoriasis is a chronic inflammatory skin condition characterized by well-circumscribed erythematous plaques with thick silvery scale. Infiltration of inflammatory cells such as lymphocytes, neutrophils, and macrophages and epidermal cell proliferation within psoriatic lesions may result in selective FDG accumulation. We present a 55-year-old patient with a 30-year history of psoriasis. Nonattenuation corrected PET/CT images demonstrated significant cutaneous FDG uptake corresponding to clinically apparent psoriatic lesions. However, in attenuation corrected (AC) FDG-PET images, the signal was substantially diminished and minimally detectable. Nonattenuation corrected FDG-PET images may be useful and preferable to AC images in assessing skin inflammation in psoriasis.

Flip-flop phenomenon in systemic sclerosis on fluorodeoxyglucose positron emission tomography/computed tomography

Systemic sclerosis (SSc) is a rare autoimmune disease, which may affect multiple organ systems. Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) can demonstrate the degree and anatomical extent of involvement in the entire body and coexisting malignancies in connective tissue diseases. We present a case of SSc with an increased 18F-FDG uptake in the cutaneous and subcutaneous tissues even higher than the neighboring skeletal muscles (“flip-flop phenomenon,” that is, an increased 18F-FDG uptake in the skin but a decreased 18F-FDG uptake in the skeletal muscles).

A Patient with Psoriatic Arthritis Imaged with FDG-PET/CT Demonstrated an Unusual Imaging Pattern with Muscle and Fascia Involvement: A Case Report

We describe the case of a patient with known history of psoriasis that presented with 1 year of unexplained fever, muscle weakness and marked weight loss, suspicious for B symptoms of a malignant origin. [(18)F]-Fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) scans demonstrated an unusual serpiginous pattern of uptake in the fascia and muscles as well as lymph node activity. Multiple histological samples, including a final PET-probe guided lymph node surgical resection, excluded malignancy and confirmed the diagnosis of reactive inflammatory changes, with a plausible diagnosis of autoimmune lymphoproliferative syndrome with associated lymphadenitis, fasciitis and myositis, possibly mediated by tumor necrosis factor (TNF) inhibitor. To our knowledge, there is no evidence of a previously reported FDG uptake pattern of fascia and muscle involvement in psoriatic arthritis.