Identification of clonal skin myeloid cells by next-generation sequencing in myelodysplasia cutis

Clinical and histological features of histiocytoid Sweet syndrome associated with VEXAS syndrome

BACKGROUND

VEXAS (Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome is caused by acquired somatic mutations in UBA1. Sweet-syndrome-like skin disorders [and especially histiocytoid Sweet syndrome (HSS)] may be associated with VEXAS syndrome.

OBJECTIVES

To characterize the clinical and histopathological features of HSS in patients with VEXAS syndrome.

METHODS

Skin biopsies with a histological diagnosis of HSS at Rennes University Medical Center (Rennes, France) between October 2011 and January 2022 were reviewed in this study. Sanger sequencing and digital polymerase chain reaction were used to screen skin, blood and bone marrow samples for UBA1 variants, and thus classify patients as having VEXAS syndrome or not. We evaluated the clinical, histological and molecular (UBA1) characteristics of patients with or without VEXAS syndrome.

RESULTS

We compared 15 skin biopsies from 7 patients found to have VEXAS syndrome and 19 skin biopsies from 15 patients without VEXAS syndrome. Persistent C-reactive protein elevation, macrocytosis, anaemia and haematological malignancies were more prevalent in patients with VEXAS syndrome [6/7 (86%), 6/7 (86%), 7/7 (100%) and 6/7 (86%), respectively] than in patients without [5/14 (36%), 6/15 (40%), 8/15 (53%) and 8/15 (53%), respectively]. These features sometimes appeared after the first skin manifestations, and a UBA1 mutation was found in the skin of five patients with VEXAS syndrome. Dermal infiltration by reniform histiocytoid cells (myeloperoxidase-positive and/or CD163-positive) and a periadnexal distribution were more frequently observed in VEXAS syndrome biopsies [15/15 (100%) and 3/15 (20%), respectively, vs. 11/19 (58%) and 0/19 (0%) in non-VEXAS syndrome biopsies, respectively].

CONCLUSIONS

Our findings might help pathologists to consider a diagnosis of VEXAS syndrome and to initiate early genetic testing.

Myelodysplasia cutis and VEXAS syndrome initially diagnosed as histiocytoid Sweet syndrome: A diagnostic pitfall

Histiocytoid Sweet syndrome (H-SS) is a histopathological variant of Sweet syndrome (SS) defined by cutaneous infiltration of immature myeloid cells morphologically resembling histiocytes. The association of H-SS with underlying malignancy, particularly myelodysplastic syndromes, is well-established. Myelodysplasia cutis (MDS-cutis) has been proposed to describe cases historically diagnosed as H-SS but characterized by shared clonality of the myeloid infiltrate in skin and bone marrow. Therefore, identifying patients who might have MDS-cutis is critical for the management of the associated hematologic malignancy. VEXAS syndrome, an adult-onset autoinflammatory disease, should also be included in the histopathologic differential diagnosis of H-SS, as it shares clinical and pathologic features with MDS-cutis. Through the presentation of two cases, we aim to highlight the defining features and key clinical implications of MDS-cutis and VEXAS syndrome.

Myelodysplasia Cutis

CONTEXT.—

Myelodysplasia cutis is an emerging concept in cutaneous neoplasia. Many of these cases were previously included under the umbrella of histiocytoid Sweet syndrome. However, with the advent of next-generation sequencing, cutaneous involvement by myelodysplastic syndrome is being increasingly recognized.

OBJECTIVE.—

To review histiocytoid Sweet syndrome and myelodysplasia cutis and discuss our current understanding of these entities. Additionally, to discuss how next-generation sequencing can be applied in the evaluation of cutaneous infiltrates of immature histiocytoid cells.

DATA SOURCES.—

The English-language literature from 2005 to 2023 on the topic of histiocytoid Sweet syndrome and myelodysplasia cutis was reviewed.

CONCLUSIONS.—

Biopsy specimens showing infiltrates of histiocytoid, immature myeloid cells may represent cutaneous involvement by myelodysplastic syndrome. Close clinical correlation is recommended in these cases. Recent studies suggest that next-generation sequencing is useful in separating myelodysplasia cutis from true histiocytoid Sweet syndrome. This distinction has important implications for patients.

From Histiocytoid Sweet Syndrome to Myelodysplasia Cutis: History and Perspectives

In 2005, a new histologic variant of Sweet syndrome (SS) has been described and termed histiocytoid SS (HSS). Clinically, patients had a typical SS, but on skin biopsy, the infiltrates were composed of immature nonblast myeloid cells. Nearly 50% of patients with HSS have myelodysplastic syndrome (MDS). HSS may be the first manifestation leading to the diagnosis of MDS. In 2015, a new category of myeloid dermatosis has been proposed, called myelodysplasia cutis, describing the specific skin infiltration by myelodysplastic cells in patients with MDS.

Myelodysplasia cutis masquerading as granulomatous dermatitis

Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic neoplasms resulting from mutations in stem cells. They carry a risk of transformation to acute myeloid leukemia. Cutaneous manifestations of MDS, including myelodysplasia cutis or infiltration by MDS tumor cells, are rare, but significantly associated with increased risk of progression to high-grade myeloid tumors. The clinical and histopathologic differential diagnosis for myelodysplasia cutis includes interstitial granulomatous dermatitis (IGD), a reactive granulomatous dermatitis (RGD) associated with systemic diseases including rheumatologic diseases, and hematologic malignancy like MDS. We report a patient with MDS who presented with myelodysplasia cutis masquerading as IGD both in a clinical and histopathological manner.

Cutaneous Manifestations of Myeloid Neoplasms Exhibit Broad and Divergent Morphologic and Immunophenotypic Features but Share Ancestral Clonal Mutations With Bone Marrow

In this study, we performed a comprehensive molecular analysis of paired skin and peripheral blood/bone marrow (BM) samples from 17 patients with cutaneous myeloid or cutaneous histiocytic-dendritic neoplasms. The cutaneous manifestations included 10 patients with cutaneous acute myeloid leukemia (c-AML), 2 patients with full or partial Langerhans cell differentiation, 2 patients with blastic plasmacytoid dendritic cell neoplasms (BPDCN), 1 patient with both Langerhans cell differentiation and BPDCN, and 2 patients with full or partial indeterminate dendritic cell differentiation. Seven of the 10 c-AML patients (70%) exhibited concurrent or subsequent marrow involvement by acute myeloid leukemia, with all 7 cases (100%) demonstrating shared clonal mutations in both the skin and BM. However, clonal relatedness was documented in one additional case that never had any BM involvement. Nevertheless, NPM1 mutations were identified in 7 of the 10 (70%) of these c-AML cases while one had KMT2A rearrangement and one showed inv(16). All 3 patients (100%) with Langerhans cell neoplasms, 2 patients with BPDCN (100%), and one of the 2 patients (50%) with other cutaneous dendritic cell neoplasms also demonstrated shared mutations between the skin and concurrent or subsequent myeloid neoplasms. Both BM and c-AML shared identical founding drivers, with a predominance of NPM1, DNMT3A, and translocations associated with monocytic differentiation, with common cutaneous-only mutations involving genes in the signal transduction and epigenetic pathways. Cutaneous histiocytic-dendritic neoplasms shared founding drivers in ASXL1, TET2, and/or SRSF2. However, in the Langerhans cell histiocytosis or histiocytic sarcoma cases, there exist recurrent secondary RAS pathway hits, whereas cutaneous BPDCN cases exhibit copy number or structural variants. These results enrich and broaden our understanding of clonally related cutaneous manifestations of myeloid neoplasms and further illuminate the highly diverse spectrum of morphologic and immunophenotypic features they exhibit.

Acute myeloid leukemia cutis with KMT2A::MLLT3 fusion presenting with leonine facies

A 63-year-old woman presented with plaques covering 60 % body-surface-area and leonine facies. Blood work showed no diagnostic aberrancies. Skin biopsy contained a malignant CD4+/CD56+ mononuclear cell population concerning for blastic plasmacytoid dendritic cell neoplasm. A later bone marrow biopsy confirmed AML with KMT2A::MLLT10 fusion detected by next-generation sequencing (NGS). This patient's LC preceded blood and marrow based symptoms of AML. NGS of the initial skin biopsy should be considered as part of diagnostic guidelines in cases with LC in the differential as this may have led to earlier diagnosis in this case and future cases.

[Dysimmune manifestations associated with myelodysplastic neoplasms and chronic myelomonocytic leukaemias]

Systemic inflammatory or autoimmune diseases (SIAD) are observed in up to a quarter of patients with myelodysplastic syndromes (MDS) or chronic myelomonocytic leukemia (CMML), with a broad clinical spectrum including asymptomatic biological abnormalities, isolated inflammatory clinical manifestations (recurrent fever, arthralgia, neutrophilic dermatoses…) or identified systemic diseases (giant cell arteritis, recurrent polychondritis…). Recent advances in molecular biology have shed new light on the pathophysiological mechanisms that link inflammatory manifestations and myeloid hemopathies, particularly in VEXAS syndrome following the identification of somatic mutations in the UBA1 gene, or in neutrophilic dermatoses with the concept of myelodysplasia cutis. Although the presence of SIAD does not seem to affect overall survival or the risk of transformation into acute myeloid leukemia, their treatment remains a challenge given the frequent high level of corticosteroid dependence as well as the poor efficacy and tolerance (cytopenias, infections) of conventional immunosuppressive agents. Recent prospective data supports the interest of a therapeutic strategy using demethylating agents and notably azacitidine to target the pathological clone.

Neutrophilic dermatoses

Neutrophilic dermatoses (ND) are a group of inflammatory skin conditions characterized by a neutrophilic infiltrate on histopathology with no evidence of infection. ND are classified based upon the localization of neutrophils within the skin and clinical features. Recent findings suggest that ND are due to two main mechanisms: i) a polyclonal hereditary activation of the innate immune system (polygenic or monogenic); or ii) a clonal somatic activation of myeloid cells such as encountered in myelodysplastic syndrome or VEXAS syndrome. ND belong to internal medicine as a great number of patients with ND suffer from an underlying condition (such as hematological malignancy, inflammatory bowel disease, auto-immune and auto-inflammatory diseases). ND are diagnoses of exclusion and physicians should always consider differential diagnoses, particularly skin infections. Here, we review the pathophysiology and classification of the main ND (i.e., subcorneal pustular dermatosis (Sneddon-Wilkinson Disease) and Intercellular IgA dermatoses, aseptic pustulosis of the folds, Sweet syndrome, neutrophilic eccrine hidradenitis, pyoderma gangrenosum, erythema elevatum diutinum, neutrophilic urticarial dermatosis and neutrophilic panniculitis), their clinical and histopathological features, and we highlight the investigations that are useful to identify ND-associated diseases and to exclude the differential diagnoses.

A rare case of late myelodysplasia cutis associated with essential thrombocythemia: A case report

Myelodysplasia cutis is a relatively new described entity that is characterized by cutaneous plaques and nodules representing dermal infiltration of myeloid immature non-blastic cells. It can be related to myelodysplastic syndromes or myeloproliferative disorders. It has distinct clinical and histopathological features in comparison with leukemia cutis. We report an unusual case of late myelodysplasia cutis in a male patient with essential thrombocythemia. It is only the second case reported to be related to this myeloproliferative disorder.

Myeloid Clonal Infiltrate Identified With Next-Generation Sequencing in Skin Lesions Associated With Myelodysplastic Syndromes and Chronic Myelomonocytic Leukemia: A Case Series

Background

Myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML) are associated with cutaneous manifestations. Next-generation sequencing (NGS) is a tool capable of identifying clonal myeloid cells in the skin infiltrate and thus better characterize the link between hematological diseases and skin lesions.

Objective

To assess whether skin lesions of MDS/CMML are clonally related to blood or bone marrow cells using NGS.

Methods

Comparisons of blood or bone marrow and skin samples NGS findings from patients presenting with MDS/CMML and skin lesions in three French hospitals.

Results

Among the 14 patients recruited, 12 patients (86%) had mutations in the skin lesions biopsied, 12 patients (86%) had a globally similar mutational profile between blood/bone marrow and skin, and 10 patients (71%) had mutations with a high variant allele frequency (>10%) found in the myeloid skin infiltrate. Mutations in TET2 and DNMT3A, both in four patients, were the most frequent. Two patients harbored a UBA1 mutation on hematopoietic samples.

Limitations

Limited number of patients and retrospective collection of the data. Blood and skin sampling were not performed at the exact same time point for two patients.

Conclusion

Skin lesions in the setting of MDS/CMML are characterized by a clonal myeloid infiltrate in most cases.