Recycled melanoma-secreted melanosomes regulate tumor-associated macrophage diversification.

Extracellular vesicles (EVs) are important mediators of communication between cells. Here, we reveal a new mode of intercellular communication by melanosomes, large EVs secreted by melanocytes for melanin transport. Unlike small EVs, which are disintegrated within the receiver cell, melanosomes stay intact within them, gain a unique protein signature, and can then be further transferred to another cell as "second-hand" EVs. We show that melanoma-secreted melanosomes passaged through epidermal keratinocytes or dermal fibroblasts can be further engulfed by resident macrophages. This process leads to macrophage polarization into pro-tumor or pro-immune cell infiltration phenotypes. Melanosomes that are transferred through fibroblasts can carry AKT1, which induces VEGF secretion from macrophages in an mTOR-dependent manner, promoting angiogenesis and metastasis in vivo. In melanoma patients, macrophages that are co-localized with AKT1 are correlated with disease aggressiveness, and immunotherapy non-responders are enriched in macrophages containing melanosome markers. Our findings suggest that interactions mediated by second-hand extracellular vesicles contribute to the formation of the metastatic niche, and that blocking the melanosome cues of macrophage diversification could be helpful in halting melanoma progression.

Sirolimus for diffuse intestinal infantile hemangioma with PHACE features: systematic review.

BACKGROUND: We report a 3-month-old female with cardiovascular anomalies and diffuse intestinal infantile hemangioma (IIH) of the small bowel suggesting possible diagnosis of PHACE syndrome (posterior fossa anomalies, hemangioma, arterial lesions, cardiac abnormalities/coarctation of the aorta, eye anomalies). The GI symptoms persisted under treatment with propranolol, whereas the addition of sirolimus led to regression of the IIH. METHODS: A systematic review was conducted using PubMed, EMBASE, and Ovid MEDLINE databases between 1982 and 2021. RESULTS: A total of 4933 articles were identified; 24 articles met inclusion criteria with 46 IIH cases. The most common GI presentations were unspecified GI bleed (40%) and anemia (38%). The most common treatments were corticosteroids (63%), surgical resection (32.6%), and propranolol (28%). Available outcomes were primarily bleeding arrest (84%). Nine cases (19.5%) were diagnosed with definite PHACE, 5 (11%) with possible PHACE, and 32 (69.5%) no PHACE. Our case presented with symptoms most consistent with those of possible PHACE and definite PHACE. No cases in this review underwent treatment with sirolimus. CONCLUSIONS: This is the first reported case of successful treatment of IIH with sirolimus. Our case, along with other patients who present with IIH and PHACE features, suggests consideration of IIH as a diagnostic criterion for PHACE syndrome. IMPACT: This is the first reported case in which sirolimus showed regression of an intestinal infantile hemangioma. This study serves to demonstrate the presentation, treatment, outcomes of intestinal infantile hemangioma, and correlation with PHACE. The potential correlation between intestinal infantile hemangioma and PHACE deserves more study in consideration of intestinal infantile hemangioma as a diagnostic criterion of PHACE.

Treatment of severe Kaposiform lymphangiomatosis positive for NRAS mutation by MEK inhibition.

BACKGROUND: Kaposiform lymphangiomatosis (KLA) is a complex lymphatic anomaly involving most commonly the mediastinum, lung, skin and bones with few effective treatments. In recent years, RAS-MAPK pathway mutations were shown to underlie the pathogenesis of several complex lymphatic anomalies. Specifically, an activating NRAS mutation (p.Q61R) was found in the majority of KLA patients. Recent reports demonstrated promising results of treatment with the MEK inhibitor, Trametinib, in patients with complex lymphatic anomalies harboring gain of function mutations in ARAF and SOS1, as well as loss of function mutation in the CBL gene, a negative regulator of the RAS-MAPK pathway. We present a 9-year-old child with a severe case of KLA harboring the typical NRAS (p.Q61R) mutation detected by plasma-derived cell free DNA, responsive to trametinib therapy. METHODS: The NRAS somatic mutation was detected from plasma cfDNA using droplet digital PCR. Concurrent in-vitro studies of trametinib activity on mutant NRAS affected lymphatic endothelial cells were performed using a three-dimensional spheroid sprouting assay. RESULTS: Trametinib treatment lead to resolution of lifelong thrombocytopenia, improvement of pulmonary function tests and wellbeing, as well as weaning from prolonged systemic steroid treatment. Concurrent studies of mutant NRAS-expressing cells showed enhanced lymphangiogenic capacity along with over activation of the RAS-MAPK and PI3K-AKT-mTOR pathways, both reversed by trametinib. CONCLUSIONS: Trametinib treatment can substantially change the prognosis of patients with RAS pathway associated lymphatic anomalies. IMPACT: This is the first description of successful trametinib treatment of a patient with KLA harboring the most characteristic NRAS p.Q61R mutation. Treatment can significantly change the prognosis of patients with RAS pathway-associated lymphatic anomalies. We devised an in vitro model of KLA enabling a reproducible method for the continued study of disease pathogenesis. Mutated NRAS p.Q61R cells demonstrated increased lymphangiogenic capacity.

Response to sirolimus in capillary lymphatic venous malformations and associated syndromes: Impact on symptomatology, quality of life, and radiographic response.

BACKGROUND: Capillary lymphatic venous malformations (CLVM) and associated syndromes, including Klippel-Trenaunay syndrome (KTS) and congenital lipomatous overgrowth, vascular malformation, epidermal nevi, skeletal, and spinal syndrome (CLOVES), are underrecognized disorders associated with high morbidity from chronic pain, recurrent infections, bleeding, and clotting complications. The rarity of these disorders and heterogeneity of clinical presentations make large-scale randomized clinical drug trials challenging. Identification of PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha [gene]) mutations in CLVM has made targeted medications, such as sirolimus, attractive treatment options. The aim of this study was to investigate the safety and efficacy of sirolimus therapy in CLVM. PROCEDURE: A combined prospective and retrospective cohort of pediatric and young adult patients with CLVM treated with sirolimus was evaluated for disease response, including symptom improvement, quality of life (QOL), and radiologic response. Sirolimus dosing regimens and toxicities were also assessed. RESULTS: Twenty-nine patients with CLVM, including KTS and CLOVES, were included. Ninety-three percent of patients reported improved QOL, and 86% had improvement in at least one symptom. Most significantly, improvement was noted in 100% of patients with bleeding and 89% with thrombotic complications with corresponding decreases in mean D-dimer (p = .008) and increases in mean fibrinogen (p = .016). No patients had progressive disease on sirolimus. Most common side effects included neutropenia, lymphopenia, infection, and aphthous ulcers/stomatitis. No toxicities were life-threatening, and none required long-term discontinuation of sirolimus. CONCLUSION: Sirolimus appears to be effective at reducing complications and improving QOL in patients with CLVM and associated syndromes. In this patient cohort, sirolimus was well tolerated and resulted in few treatment-related toxicities.

Mycosis Fungoides in Solid-Organ Transplant Recipients: A Multicenter Retrospective Cohort Study.

BACKGROUND: Mycosis fungoides (MF) in solid-organ transplant recipients (SOTRs) is rare, with limited data on disease characteristics. OBJECTIVE: The aim was to study the characteristics of MF in SOTRs with an emphasis on the immunosuppressive therapy. METHODS: A retrospective cohort of patients diagnosed with MF, who were also SOTRs, were followed at 3 cutaneous lymphoma outpatient clinics, between January 2010 and February 2022. RESULTS: Ten patients were included (7 male; median ages at transplantation and at diagnosis of MF were 33 and 48 years, respectively; 40% were diagnosed before the age of 18 years). Median time from transplantation to diagnosis of MF was 8 years (range 0.5-22). Transplanted organs and immunosuppressive treatments included: liver (n = 5; 4 treated with tacrolimus, 1 with tacrolimus and prednisone), kidney (n = 3), liver and kidney (n = 1), and heart (n = 1), all treated with mycophenolic acid, tacrolimus, and prednisone. Nine had early-stage MF (IA - 4, IB - 5; 40% with early folliculotropic MF), treated with skin-directed therapies, in 2 combined with acitretin, achieving partial/complete response. One patient had advanced-stage MF (IIIA) with folliculotropic erythroderma, treated with ultraviolet A and narrow-band ultraviolet B with acitretin, achieving partial response. Immunosuppression was modified in 3. At last follow-up (median 4 years, range 1-8), no stage progression was observed; 5 had no evidence of disease, 5 had active disease (IA/IB - 4, III - 1). CONCLUSIONS: MF in SOTRs is usually diagnosed at an early stage, with overrepresentation of folliculotropic MF, and of children. Immunosuppressive therapy alterations, not conducted in most patients, should be balanced against the risk of organ compromise/rejection. Disease course was similar to MF in immunocompetent patients, during the limited time of follow-up.

Interactions of Melanoma Cells with Distal Keratinocytes Trigger Metastasis via Notch Signaling Inhibition of MITF.

The most critical stage in initiation of melanoma metastasis is the radial to vertical growth transition, yet the triggers of this transition remain elusive. We suggest that the microenvironment drives melanoma metastasis independently of mutation acquisition. Here we examined the changes in microenvironment that occur during melanoma radial growth. We show that direct contact of melanoma cells with the remote epidermal layer triggers vertical invasion via Notch signaling activation, the latter serving to inhibit MITF function. Briefly, within the native Notch ligand-free microenvironment, MITF, the melanocyte lineage master regulator, binds and represses miR-222/221 promoter in an RBPJK-dependent manner. However, when radial growth brings melanoma cells into contact with distal differentiated keratinocytes that express Notch ligands, the activated Notch intracellular domain impairs MITF binding to miR-222/221 promoter. This de-repression of miR-222/221 expression triggers initiation of invasion. Our findings may direct melanoma prevention opportunities via targeting specific microenvironments.

White epidermal nevus as an early sign of tuberous sclerosis complex-A case series.

Tuberous sclerosis complex (TSC) is a rare genetic disease with neurocutaneous manifestations, often presenting initially to the dermatology clinic. We report a cohort of neonates who presented with a novel finding of white epidermal nevus and were eventually diagnosed with TSC. White epidermal nevus may be yet another dermatological finding that may aid in the early diagnosis of TSC.

Efficacy of Systemic Treatment for Leishmania tropica Cutaneous Leishmaniasis.

The effectiveness of systemic treatment for Leishmania tropica cutaneous leishmaniasis remains unclear. The purpose of the study is to evaluate the efficacy and safety of systemic treatments for L. tropica cutaneous leishmaniasis. This retrospective study was performed in 114 patients. Systemic treatments included liposomal amphotericin B and sodium stibogluconate. All patients underwent systemic treatment for L. tropica cutaneous leishmaniasis. Favourable treatment responses were recorded in 72.5% and 70.2% of the patients in the liposomal amphotericin B and sodium stibogluconate groups, respectively; 25.3% and 46% of those in the liposomal amphotericin B and sodium stibogluconate groups respectively, experienced at least one adverse effect. Lesions in cartilaginous areas were associated with higher treatment failure. Prior topical or systemic treatment increased the chance of future systemic treatment success. Liposomal amphotericin B was associated with a shorter intravenous treatment duration and better safety profile. Thus, liposomal amphotericin B is the treatment of choice for L. tropica cutaneous leishmaniasis.

Clinical Characteristics, Management, and Natural History of Chronic Inducible Urticaria in a Pediatric Cohort.

BACKGROUND: Some forms of chronic urticaria (CU) can be specifically attributed to a response to a definite trigger, referred to as chronic inducible urticaria (CIndU). We aimed to assess the demographics, clinical characteristics, comorbidities, natural history, and management of pediatric patients with CIndU. METHODS: Over a 6-year period, children presenting to the allergy clinic at the Montreal Children's Hospital (MCH) with CIndU were prospectively recruited. CU was defined as the presence of wheals and/or angioedema, occurring for at least 6 weeks. A standardized diagnostic test was used to establish the presence of a specific form of urticaria. Resolution was defined as the absence of hives for 1 year without treatment. RESULTS: Sixty-four patients presented with CIndU, of which 51.6% were male, with a median age of 12.5 (interquartile range 7.3, 15.9) years. Cold CU and cholinergic CU were the most common subtypes (60.3 and 41.3%, respectively). Basophil counts were undetectable in 48.4% of the cases, and C-reactive protein levels were elevated in 7.8% of patients. Of all cases, 71.4% were controlled with second-generation antihistamines. The resolution rate was of 45.3% (95% confidence interval 33.1-57.5%), based on per-protocol population within the 6-year course of the study. Resolution was more likely in patients who presented with well-controlled urticaria control test scores and elevated CD63 counts and in those suffering from thyroid comorbidity. CONCLUSION: The natural history of CIndU resolution in pediatric patients was relatively low and was associated with elevated CD63 levels, as well as thyroid comorbidity.

Cutaneous Adverse Events to Targeted Therapies and Immuno-therapies in Children: A Retrospective Study of 103 Patients from Two Tertiary Haemato-Oncology Referral Centres.

Targeted medications and immunotherapies are being developed to specifically target the pathways involved in tumours. There is limited experience with these new medications and their cutaneous side-effects in the paediatric population. A retrospective study of all paediatric oncological patients treated with targeted therapies and immunotherapies between 1 January 2013 and 1 August 2020 was carried out in 2 haemato-oncological referral centres. A total of 103 children were included in the study. The median (interquartile range) age was 13 years (8.4-16.9), male:female ratio 1.5:1, median (interquartile range) follow-up was 7 months (2-18). Fifty (48%) of the children developed cutaneous adverse events. Treatment was discontinued in only 3 (6%) cases and was altered in only (2%) 1 case due to a cutaneous adverse event. When targeted therapies and immunotherapies for tumours in children are used, there is an increased incidence of cutaneous adverse events. Nevertheless, treatment modification or discontinuation due to cutaneous side-effects is rarely needed.

The effect of narrow-band ultraviolet B radiation on sleep, happiness, and appetite: A prospective cohort study.

BACKGROUND: The health benefits of sunlight are well documented, including the effects on happiness and sleep. However, only a few studies have investigated the benefits of artificial narrow-band ultraviolet B (NB-UVB) radiation. OBJECTIVES: To investigate the effect of NB-UVB on sleep quality, happiness, and appetite. METHODS: Patients from a single phototherapy unit were selected, and their epidemiological characteristics were documented. Subjects were asked to complete questionnaires including the Pittsburg Sleep Quality Index (PSQI), Subjective Happiness Scale (SHS), and the Simplified Nutritional Appetite Questionnaire (SNAQ) 4 weeks before and after the initiation of the NB-UVB therapy. The sample consisted of 52 patients. RESULTS: Four weeks after the initiation of NB-UVB sessions, sleep quality was significantly improved (the PSQI decreased from 6.5 to 5.23 (t = -3.52, P < .01). In contrast, subjective happiness did not improve (the SHS decreased from baseline 5.5 to 5.2, P > .05). Similarly, appetite did not change (the SNAQ score increased from baseline 14.75 to 15.05, P > .05) and body mass index was not affected by phototherapy. In general, men were found to have better sleep quality before and after UV light therapy. CONCLUSION: Our data suggest that NB-UVB exposure over 4 weeks improves sleep quality; however, it does not influence happiness or appetite.

An Israeli tuberous sclerosis cohort: the efficacy of different anti-epileptic strategies.

AIM: We aimed to describe the experience of a large single-center cohort for the clinical, radiological, and genetic characteristics, as well as to determine the efficacy of different anti-epileptic strategies in children and adults with tuberous sclerosis complex (TSC). METHODS: We carried out a historical cohort study on 91 TSC patients treated in a single center between 2008 and 2018. RESULTS: Our cohort comprised 46 males and 45 females, with a median age of 15.6 years at the last follow-up. Mean follow-up time was 2.5 ± 0.75-5.5 years (range 0-9.5 years). Of those tested, a disease-causing mutation was identified in 90% of patients, 53% in TSC2, and 37% in TSC1. Epilepsy prevalence was similar among TSC1 and TSC2 mutated patients. The most common radiological finding were cortical tubers in 95% of patients, while subependymal giant cell astrocytoma (SEGA) were detected in 36% of patients. Notably, infantile spasms (IS) were diagnosed in 29%, with SEGA representing the only finding significantly different in prevalence between those with and without IS (62% vs. 28%, respectively, p = 0.009). Lastly, we did not find any difference in efficacy between three anti-epileptic treatments: Vagus nerve stimulation (VNS), CBD-based products, and the ketogenic diet, all showing approximately 30%-40% response rates. SIGNIFICANCE: Altogether, we provide a comprehensive description of our experience in treating TSC, which could serve to expand current knowledge of the disease and its treatments.

Inflammatory bowel disease presenting with pyodermatitis-pyostomatitis vegetans in a pediatric patient: A case report and review of the literature.

Pyodermatitis-pyostomatitis vegetans (PD-PSV) is rarely reported in the pediatric population. Here, we provide a review of pediatric PD-PSV in the literature and report a case of widespread PD-PSV in a 15-year-old male without a previous history of inflammatory bowel disease or gastrointestinal symptoms. Clinical, histological, and immunopathological workup established PD-PSV and revealed subclinical Crohn's disease. Treatment with infliximab was effective in inducing rapid resolution of the lesions.

Successful Introduction of Human Renovascular Units into the Mammalian Kidney.

BACKGROUND: Cell-based therapies aimed at replenishing renal parenchyma have been proposed as an approach for treating CKD. However, pathogenic mechanisms involved in CKD such as renal hypoxia result in loss of kidney function and limit engraftment and therapeutic effects of renal epithelial progenitors. Jointly administering vessel-forming cells (human mesenchymal stromal cells [MSCs] and endothelial colony-forming cells [ECFCs]) may potentially result in in vivo formation of vascular networks. METHODS: We administered renal tubule-forming cells derived from human adult and fetal kidneys (previously shown to exert a functional effect in CKD mice) into mice, alongside MSCs and ECFCs. We then assessed whether this would result in generation of "renovascular units" comprising both vessels and tubules with potential interaction. RESULTS: Directly injecting vessel-forming cells and renal tubule-forming cells into the subcutaneous and subrenal capsular space resulted in self-organization of donor-derived vascular networks that connected to host vasculature, alongside renal tubules comprising tubular epithelia of different nephron segments. Vessels derived from MSCs and ECFCs augmented in vivo tubulogenesis by the renal tubule-forming cells. In vitro coculture experiments showed that MSCs and ECFCs induced self-renewal and genes associated with mesenchymal-epithelial transition in renal tubule-forming cells, indicating paracrine effects. Notably, after renal injury, renal tubule-forming cells and vessel-forming cells infused into the renal artery did not penetrate the renal vascular network to generate vessels; only administering them into the kidney parenchyma resulted in similar generation of human renovascular units in vivo. CONCLUSIONS: Combined cell therapy of vessel-forming cells and renal tubule-forming cells aimed at alleviating renal hypoxia and enhancing tubulogenesis holds promise as the basis for new renal regenerative therapies.

Decreased A-to-I RNA editing as a source of keratinocytes' dsRNA in psoriasis.

Recognition of dsRNA molecules activates the MDA5-MAVS pathway and plays a critical role in stimulating type-I interferon responses in psoriasis. However, the source of the dsRNA accumulation in psoriatic keratinocytes remains largely unknown. A-to-I RNA editing is a common co- or post-transcriptional modification that diversifies adenosine in dsRNA, and leads to unwinding of dsRNA structures. Thus, impaired RNA editing activity can result in an increased load of endogenous dsRNAs. Here we provide a transcriptome-wide analysis of RNA editing across dozens of psoriasis patients, and we demonstrate a global editing reduction in psoriatic lesions. In addition to the global alteration, we also detect editing changes in functional recoding sites located in the IGFBP7, COPA, and FLNA genes. Accretion of dsRNA activates autoimmune responses, and therefore the results presented here, linking for the first time an autoimmune disease to reduction in global editing level, are relevant to a wide range of autoimmune diseases.

Cutaneous Leishmaniasis Treated with Miltefosine: A Case Series of 10 Paediatric Patients.

Cutaneous leishmaniasis poses a therapeutic challenge in the paediatric population. The aim of this study was to assess the efficacy and safety of miltefosine treatment for Old World cutaneous leishmaniasis in paediatric patients. A multicentre retrospective review of 10 children (≤ 18 years of age) with cutaneous leishmaniasis treated with miltefosine in Israel was performed. Mean ± standard deviation age at diagnosis was 9.1 ± 5.0 years. The Leishmania species diagnosed was L. tropica in 8 cases and Leishmania major in 2 cases. Mean ± standard deviation duration of treatment was 44.8 ± 20.6 days, with a mean follow-up period of 12.1 ± 17.1 months. Complete response was noted in 8 (80%) patients. Treatment failure was noted in 2 (20%) cases. Side-effects related to the medication were minimal. In conclusion, oral miltefosine may be an effective and safe treatment for Old World cutaneous leishmaniasis caused by Leishmania tropica or Leishmania major in children. However, further studies are warranted to draw a definite conclusion.

Cutaneous Leishmaniasis Treated with Miltefosine: A Case Series of 10 Paediatric Patients.

Cutaneous leishmaniasis poses a therapeutic challenge in the paediatric population. The aim of this study was to assess the efficacy and safety of miltefosine treatment for Old World cutaneous leishmaniasis in paediatric patients. A multicentre retrospective review of 10 children (≤ 18 years of age) with cutaneous leishmaniasis treated with miltefosine in Israel was performed. Mean ± standard deviation age at diagnosis was 9.1 ± 5.0 years. The Leishmania species diagnosed was L. tropica in 8 cases and Leishmania major in 2 cases. Mean ± standard deviation duration of treatment was 44.8 ± 20.6 days, with a mean follow-up period of 12.1 ± 17.1 months. Complete response was noted in 8 (80%) patients. Treatment failure was noted in 2 (20%) cases. Side-effects related to the medication were minimal. In conclusion, oral miltefosine may be an effective and safe treatment for Old World cutaneous leishmaniasis caused by Leishmania tropica or Leishmania major in children. However, further studies are warranted to draw a definite conclusion.

Subcutaneous granuloma annulare mimicking dermatomyositis.

We present three children who presented with papules and plaques over the knuckles, mimicking Gottron's papules of juvenile dermatomyositis, as well as subcutaneous nodules over the joints of the extremities that were initially thought to represent calcinosis cutis. However, thorough clinical and laboratory evaluation, as well as imaging, failed to support this diagnosis. Skin biopsies were consistent with a diagnosis of subcutaneous granuloma annulare. This unique phenotype of granuloma annulare should be recognized in order to prevent erroneous diagnosis and treatment.

The effect of natural matrix biopolymer membrane on hard-to-heal venous leg ulcers: a pilot randomised clinical trial.

OBJECTIVE: The aim of this study was to evaluate the therapeutic effects of natural matrix biopolymer membrane (NMBM) in the treatment of venous leg ulcers (VLUs). METHOD: Patients exhibiting one or more VLU were assigned to a test group receiving NMBM or to a control group receiving conventional treatment. Patients exhibiting venous insufficiency-related ulcers within 0.1-170cm2 were included. Efficacy was assessed based on ulcer size and visual analogue scale (VAS) pain scores at baseline and at weeks one, two and four. Ulcer size and pain were compared between groups using a two-way ANOVA. RESULTS: In this study, 25 patients with 32 VLUs (NMBM group: 14 patients with 17 ulcers; control group: 11 patients with 15 ulcers) were included in the final analysis. At four weeks after baseline measurements, the mean percentage change in VLU area of patients in the NMBM group was 61.6% (95% CI: 40.3-82.9) compared with 84.1% (95% CI: 56.5-111.7) for control group patients. Additionally, the mean percentage change in VLU volume of NMBM group patients was 51.2% (95% CI: 31.8-70.6) compared with 84.0% (95% CI: 57.0-121.0) for control group patients. The NMBM group patients exhibited a mean decrease of 0.38 (95% CI: -0.85-1.61) in VAS pain score over four weeks, compared with a mean decrease of 0.13 (95% CI: -1.32-1.58) for control group patients. No significant differences in VLU area (p=0.210), volume (p=0.122) or VAS pain score (p=0.460) were shown between groups. CONCLUSION: NMBM was found to be as effective and safe as the control group treatments. This pilot study suggests NMBM can be used safely to promote ulcer healing.

Novel MALT1 Mutation Linked to Immunodeficiency, Immune Dysregulation, and an Abnormal T Cell Receptor Repertoire.

MALT1 (mucosa-associated lymphoid tissue lymphoma-translocation gene 1) is an intracellular signaling protein that activates NFκB and is crucial for both the adaptive and innate immune responses. Only 6 patients with immune deficiencies secondary to inherited mutations in the MALT1 gene have been described. PURPOSE: To provide clinical and immunological insights from 2 patients diagnosed with MALT1 immunodeficiency syndrome due to a novel MALT1 mutation. METHODS: Two cousins with suspected combined immunodeficiency underwent immunological and genetic work-up, including lymphocyte phenotyping, lymphocyte activation by mitogen stimulation, and next-generation sequencing (NGS) of T cell receptor gamma chain (TRG) repertoire. Whole exome sequencing was performed to identify the underlying genetic defect. RESULTS: Clinical findings included recurrent infections, failure to thrive, lymphadenopathy, dermatitis, and autoimmunity. Immune work-up revealed lymphocytosis, low to normal levels of immunoglobulins, absence of regulatory T cells, and low Th17 cells. A normal proliferative response was induced by phytohemagglutinin and IL-2 but was diminished with anti-CD3. TRG repertoire was diverse with a clonal expansion pattern. Genetic analysis identified a novel autosomal recessive homozygous c.1799T>A; p. I600N missense mutation in MALT1. MALT1 protein expression was markedly reduced, and in vitro IL-2 production and NFκB signaling pathway were significantly impaired. CONCLUSIONS: Two patients harboring a novel MALT1 mutation presented with signs of immune deficiency and dysregulation and were found to have an abnormal T cell receptor repertoire. These findings reinforce the link between MALT1 deficiency and combined immunodeficiency. Early diagnosis is crucial, and curative treatment by hematopoietic stem cell transplantation may be warranted.