Amino acids are essential for protein synthesis, epigenetic modification through the methylation of histones, and the maintenance of a controlled balance of oxidoreduction via the production of glutathione and are precursors of certain neurotransmitters. T lymphocytes are particularly sensitive to fluctuations in amino acid levels. During evolution, the production of amino-acid catabolizing enzymes by mainly antigen-presenting cells has become a physiological mechanism to control T-cell activation and polarization. The action of these enzymes interferes with TCR and co-stimulation signaling, allowing tuning of the T-cell response. These capacities can be altered in certain pathological conditions, with relevant consequences for the development of disease.

Cutaneous γ/δ T-cell lymphoma (CGD-TCL) is a recent entity described in the newly revised World Health Organization-European Organization for Research and Treatment of Cancer classification of cutaneous lymphomas, and is characterized by the γ/δ T-cell receptor expression on atypical lymphocytes. Only a few cases of primary CGD-TCL have been reported, with an extremely aggressive course (median survival time of 15 months). We describe 2 atypical cases of CGD-TCL. The first case was initially misdiagnosed as an inflammatory panniculitis due to the granulomatous infiltrate on the skin biopsy specimen. Diagnosis was confirmed using δ PCR that revealed γ/δ T-cell clonal expansion. The evolution was marked by predominant γ/δ T-cell infiltrate with diffuse body fat involvement as seen on positron emission tomography-computed tomography. The second case is the first described Epstein-Barr virus (EBV)-associated CGD-TCL with a rapidly fatal evolution. CGD-TCL is also a heterogeneous entity and δ PCR and EBV-encoded RNA probe to detect an EBV latent infection may help diagnose and characterize these cutaneous lymphomas.

Background: Cardiac light chain amyloidosis (AL-CA) patients often die within three months of starting chemotherapy. Chemotherapy for non-immunoglobulin M gammopathy with AL-CA frequently includes bortezomib (Bor), cyclophosphamide (Cy), and dexamethasone (D). We previously reported that NT-ProBNP levels can double within 24h of dexamethasone administration, suggesting a deleterious impact on cardiac function. In this study, we evaluate the role of dexamethasone in early cardiovascular mortality during treatment. Methods and findings: We retrospectively assessed 100 de novo cardiac AL patients (62% male, mean age 68 years) treated at our institute between 2009 and 2018 following three chemotherapy regimens: CyBorDComb (all initiated on day 1; 34 patients), DCyBorSeq (D, day 1; Cy, day 8; Bor, day 15; 17 patients), and CyBorDSeq (Cy, day 1; Bor, day 8; D, day 15; 49 patients). The primary endpoint was cardiovascular mortality and cardiac transplantation at days 22 and 455. At day 22, mortality was 20.6% with CyBorDComb, 23.5% with DCyBorSeq, and 0% with CyBorDSeq (p = 0.003). At day 455, mortality was not significantly different between regimens (p = 0.195). Acute toxicity of dexamethasone was evaluated on myocardial function using a rat model of isolated perfused heart. Administration of dexamethasone induced a decrease in left ventricular myocardium contractility and relaxation (p<0.05), supporting a potential negative inotropic effect of dexamethasone in AL-CA patients with severe cardiac involvement. Conclusion: Delaying dexamethasone during the first chemotherapy cycle reduces the number of early deaths without extending survival. It is clear that dexamethasone is beneficial in the long-term treatment of patients with AL-CA. However, the initial introduction of dexamethasone during treatment is critical, but may be associated with early cardiac deaths in severe CA. Thus, it is important to consider the dosage and timing of dexamethasone introduction on a patient-severity basis. The impact of dexamethasone in the treatment of AL-CA needs further investigation.

The causal protein of amyloid light‐chain (AL) amyloidosis is a monoclonal immunoglobulin free light chain (mFLC), which must be quantified in the serum for patient diagnosis and monitoring. Several manufacturers commercialize immunoassays that quantify total kappa (κ) and lambda (λ) FLC, but results can differ greatly between these tests. Here, we compared a recently developed enzyme‐linked immunosorbent assay (ELISA) (Sebia) with N‐Latex immunonephelometry (Siemens) in 96 patients diagnosed with AL amyloidosis (histologically confirmed) and 48 non‐AL patients sent to our referral center for suspicion of cardiac amyloidosis. ELISA free‐light chain difference (dFLC) were lower than N‐Latex values, and agreement between methods was reduced in the case of involved λ FLC. Diagnosis sensitivity and specificity were >85% with both assays. A receiver operating characteristic analysis indicated that ELISA performances could be improved by using a higher value for the lower limit of the κ/λ ratio. We also assessed Freelite (The Binding Site) in a subgroup of these same AL patients, including 18 cases with normal κ/λ ratio by at least one assay. Only two patients had normal κ/λ ratio with all three assays. Overall, ELISA demonstrated slightly lower sensitivity than N‐Latex but may be an alternative to nephelometry/turbidimetry in certain difficult cases.