H syndrome: The first 79 patients

Combination of four features of SLC29A3 spectrum disorder in a child: A case report

SLC29A3 spectrum disorder, also known as histiocytosis-lymphadenopathy plus syndrome (HLPS), presents a wide variety of multi-systemic manifestations that can be mistaken for other conditions. Herein, we report a 9-year-old girl who presented with a complex clinical presentation since birth, including chronic generalized lymphadenopathy in association with hepatosplenomegaly, short stature, flexion contractures, hearing loss, hyperpigmentation, and heart anomalies. She was ultimately diagnosed with the SLC29A3 spectrum disorder.

New discoveries in the genetics and genomics of systemic juvenile idiopathic arthritis

INTRODUCTION

Systemic juvenile idiopathic arthritis (sJIA) is a severe inflammatory condition with onset in childhood. It is sporadic, but elements of its stereotypical innate immune responses are likely genetically encoded by both common variants with small effect sizes and rare variants with larger effects.

AREAS COVERED

Genomic investigations have defined the unique genetic architecture of sJIA. Identification of the class II HLA locus as the strongest sJIA risk factor for the first time brought attention to T lymphocytes and adaptive immune mechanisms in sJIA. The importance of the human leukocyte antigen (HLA) locus was reinforced by recognition that HLA-DRB1*15 alleles are strongly associated with development of drug reactions and sJIA-associated lung disease (sJIA-LD). At the IL1RN locus, genetic variation relates to both risk of sJIA and may also predict non-response to anakinra. Finally, rare genetic variants may have critical roles in disease complications, such as homozygous LACC1 mutations in families with an sJIA-like illness, and hemophagocytic lymphohistiocytosis (HLH) gene variants in some children with macrophage activation syndrome (MAS).

EXPERT OPINION

Genetic and genomic analysis of sJIA holds great promise for both basic discovery of the course and complications of sJIA, and may help guide personalized medicine and therapeutic decision-making.

Cases with the H syndrome presenting with skin and bone findings

BACKGROUND

The H syndrome is an autosomal recessive disease characterized by hyperpigmentation, hypertrichosis and sensorineural hearing loss.

METHODS

A mutation in the coding of the human equilibrative nucleoside transporter 3 (hENT3) within the SLC29A3 gene on chromosome 10q22 leads to the manifestation of this disease. In this report, we present two cases of H syndrome.

RESULTS

The first patient exhibits hyperpigmentation, hypogonadism, Type 1 diabetes mellitus, arthritis and osteoporosis. The second patient experiences hyperpigmentation, hypertrichosis, osteopenia and hypogonadism.

CONCLUSION

Our objective is to broaden the clinical spectrum of H syndrome, highlighting the involvement of arthritis, hyperinflammation and low bone mineral density in individuals with this disorder.

Current phenotypic and genetic spectrum of syndromic deafness in Tunisia: paving the way for precision auditory health

Hearing impairment (HI) is a prevalent neurosensory condition globally, impacting 5% of the population, with over 50% of congenital cases attributed to genetic etiologies. In Tunisia, HI underdiagnosis prevails, primarily due to limited access to comprehensive clinical tools, particularly for syndromic deafness (SD), characterized by clinical and genetic heterogeneity. This study aimed to uncover the SD spectrum through a 14-year investigation of a Tunisian cohort encompassing over 700 patients from four referral centers (2007-2021). Employing Sanger sequencing, Targeted Panel Gene Sequencing, and Whole Exome Sequencing, genetic analysis in 30 SD patients identified diagnoses such as Usher syndrome, Waardenburg syndrome, cranio-facial-hand-deafness syndrome, and H syndrome. This latter is a rare genodermatosis characterized by HI, hyperpigmentation, hypertrichosis, and systemic manifestations. A meta-analysis integrating our findings with existing data revealed that nearly 50% of Tunisian SD cases corresponded to rare inherited metabolic disorders. Distinguishing between non-syndromic and syndromic HI poses a challenge, where the age of onset and progression of features significantly impact accurate diagnoses. Despite advancements in local genetic characterization capabilities, certain ultra-rare forms of SD remain underdiagnosed. This research contributes critical insights to inform molecular diagnosis approaches for SD in Tunisia and the broader North-African region, thereby facilitating informed decision-making in clinical practice.

Rheumatological complaints in H syndrome: from inflammatory profiling to target treatment in a case study

BACKGROUND

H Syndrome is a rare genetic condition caused by biallelic pathogenic variants in the SLC29A3 gene. It is characterized by a wide range of clinical manifestations, many of which are related to the immune-rheumatological field. These include scleroderma-like skin changes, deforming arthritis, and enlarged lymph nodes. The condition also features cardiac and endocrine defects, as well as hearing loss, for which the immune pathogenesis appears less clear. Immunomodulatory medications have been shown to improve many symptoms in recent experiences.

CASE PRESENTATION

A 21-year-old girl was referred to our institute after being diagnosed with H syndrome. Her medical history was characterized by the development of finger and toe deformities, which developed since the first years of life and progressively worsened with clinodactyly. At 6 years of age, she was diagnosed with diabetes mellitus without typical autoantibodies and with bilateral sensorineural hearing loss. She also complained of frequent episodes of lymphadenopathy, sometimes with colliquation and growth retardation due to pancreatic insufficiency. It wasn't until the genetic diagnosis of H syndrome that the continual increase in acute phase reactants was noticed, suggesting that an immunological pathogenesis may be the source of her problems. During her visit to our institute, she reported serious pain in both feet and hands and difficulty walking due to knee arthritis and muscle contractures. Conventional therapy with steroid injection in affected joints and methotrexate only led to partial improvement. After a thorough assessment of her inflammatory profile showing a high interferon score, the girl received treatment with baricitinib. Furthermore, based on recent data showing that SLC29A3 deficiency results in interferon production because of Toll-like Receptor 7 activation in lysosomes, hydroxychloroquine was also added. The combination of the two drugs resulted for the first time in a rapid and persistent normalization of inflammatory markers, paralleled by a dramatic improvement in symptoms.

CONCLUSIONS

We describe the results of inhibiting IFN inflammation in H syndrome and discuss how JAK inhibitors and antimalarials might represent a mechanistically based treatment for this orphan drug disorder.

Equilibrative nucleotide transporter ENT3 (SLC29A3): A unique transporter for inherited disorders and cancers

As a crucial gene associated with diseases, the SLC29A3 gene encodes the equilibrative nucleoside transporter 3 (ENT3). ENT3 plays an essential regulatory role in transporting intracellular hydrophilic nucleosides, nucleotides, hydrophilic anticancer and antiviral nucleoside drugs, energy metabolism, subcellular localization, protein stability, and signal transduction. The mutation and inactivation of SLC29A3 are intimately linked to the occurrence, development, and prognosis of various human tumors. Moreover, many hereditary human diseases, such as H syndrome, pigmentary hypertrichosis and non-autoimmune insulin-dependent diabetes mellitus (PHID) syndrome, Faisalabad histiocytosis (FHC), are related to SLC29A3 mutations. This review explores the mechanisms of SLC29A3 mutations and expression alterations in inherited disorders and cancers. Additionally, we compile studies on the inhibition of ENT3, which may serve as an effective strategy to potentiate the anticancer activity of chemotherapy. Thus, the synopsis of genetics, permeant function and drug therapy of ENT3 provides a new theoretical and empirical foundation for the diagnosis, prognosis of evaluation and treatment of various related diseases.

Hyperglycemia with hypogonadism and growth hormone deficiency in a 17-year-old male with H syndrome: the first case report from Syria

BACKGROUND

The nucleoside transport capabilities of the human equilibrative nucleoside transporter-3 (hENT3) are disrupted by mutations in SLC29A3 (10q22.2), which are genes for the nucleoside transporter and are the cause of the unusual autosomal recessive disease known as H syndrome. As a result, histiocytic cells invade a number of organs.

CASE PRESENTATION

A 17-year-old Syrian male was admitted to the internal medicine department with a one-month history of polyuria, polydipsia, general weakness, and pallor. He had a history of progressive bilateral sensorineural hearing loss and failure to gain weight for three years. Physical examination revealed various abnormalities, including scrotal mass, small penis and testicles, absence of pubic and axillary hair, joint abnormalities, short stature, hallux valgus, fibrous protrusion near the navel, and hyperpigmented non-itchy painful skin plaques. Clinical signs along with laboratory test results confirmed hyperglycemia, primary hypogonadism, osteopenia, and growth hormone deficiency. After a review of the relevant medical literature, this patient's presentation of hyperglycemia with hypogonadism, hyperpigmentation, hallux valgus, hearing loss, hematological abnormalities, and short stature suggested the diagnosis of H syndrome. The patient received treatment with insulin and testosterone, leading to a significant improvement in his presenting symptoms.

CONCLUSIONS

H syndrome is a very rare condition, and the fact that the first case has only recently been reported in Syria serves to emphasize how rare it is. H Syndrome should be suspected if a patient has short stature with signs of hyperglycemia and other endocrine and cutaneous abnormalities. We are reporting this case to increase physicians' awareness of this exceedingly rare and unique syndrome.

Loss of function of ENT3 drives histiocytosis and inflammation through TLR-MAPK signaling

Histiocytoses are inflammatory myeloid neoplasms often driven by somatic activating mutations in mitogen-activated protein kinase (MAPK) cascade genes. H syndrome is an inflammatory genetic disorder caused by germ line loss-of-function mutations in SLC29A3, encoding the lysosomal equilibrative nucleoside transporter 3 (ENT3). Patients with H syndrome are predisposed to develop histiocytosis, yet the mechanism is unclear. Here, through phenotypic, molecular, and functional analysis of primary cells from a cohort of patients with H syndrome, we reveal the molecular pathway leading to histiocytosis and inflammation in this genetic disorder. We show that loss of function of ENT3 activates nucleoside-sensing toll-like receptors (TLR) and downstream MAPK signaling, inducing cytokine secretion and inflammation. Importantly, MEK inhibitor therapy led to resolution of histiocytosis and inflammation in a patient with H syndrome. These results demonstrate a yet-unrecognized link between a defect in a lysosomal transporter and pathological activation of MAPK signaling, establishing a novel pathway leading to histiocytosis and inflammation.

TLR7/8 stress response drives histiocytosis in SLC29A3 disorders

Loss-of-function mutations in the lysosomal nucleoside transporter SLC29A3 cause lysosomal nucleoside storage and histiocytosis: phagocyte accumulation in multiple organs. However, little is known about the mechanism by which lysosomal nucleoside storage drives histiocytosis. Herein, histiocytosis in Slc29a3-/- mice was shown to depend on Toll-like receptor 7 (TLR7), which senses a combination of nucleosides and oligoribonucleotides (ORNs). TLR7 increased phagocyte numbers by driving the proliferation of Ly6Chi immature monocytes and their maturation into Ly6Clow phagocytes in Slc29a3-/- mice. Downstream of TLR7, FcRγ and DAP10 were required for monocyte proliferation. Histiocytosis is accompanied by inflammation in SLC29A3 disorders. However, TLR7 in nucleoside-laden splenic monocytes failed to activate inflammatory responses. Enhanced production of proinflammatory cytokines was observed only after stimulation with ssRNAs, which would increase lysosomal ORNs. Patient-derived monocytes harboring the G208R SLC29A3 mutation showed enhanced survival and proliferation in a TLR8-antagonist-sensitive manner. These results demonstrated that TLR7/8 responses to lysosomal nucleoside stress drive SLC29A3 disorders.

H syndrome treated with Tocilizumab: two case reports and literature review

H syndrome is a rare autosomal recessive genetic disorder characterized by the following clinical features: cutaneous hyperpigmentation, hypertrichosis, hepatosplenomegaly, heart anomalies, hearing loss, hypogonadism, short stature, hallux valgus, hyperglycemia, fixed flexion contractures of the toe joints, and the proximal interphalangeal joints. In rare cases, autoinflammatory and lymphoproliferative manifestations have also been reported. This disorder is due to loss-of-function mutations in SLC29A3 gene, which encode the equilibrative nucleoside transporter ENT3. This deficiency leads to abnormal function and proliferation of histiocytes. H syndrome is part of the R-group of histiocytosis. We report two different cases, one was diagnosed in adulthood and the other in childhood. The first case reported is a 37-year-old woman suffering from H syndrome with an autoinflammatory systemic disease that begins in adulthood (fever and diffuse organ's infiltration) and with cutaneous, articular, auditory, and endocrinological manifestations since childhood. The second case reported is a 2-year-old girl with autoinflammatory, endocrine, and cutaneous symptoms (fever, lymphadenopathy, organomegaly, growth delay, and cutaneous hyperpigmentation). Homozygous mutations in SLC29A3 confirmed the diagnosis of H syndrome in both cases. Each patient was treated with Tocilizumab with a significant improvement for lymphoproliferative, autoinflammatory, and cutaneous manifestations. Both cases were reported to show the multiple characteristics of this rare syndrome, which can be diagnosed either in childhood or in adulthood. In addition, an overview of the literature suggested Tocilizumab efficiency.

How I Diagnose Rosai-Dorfman Disease

OBJECTIVES

Rosai-Dorfman disease (RDD) is one of 3 major types of histiocytosis, along with Erdheim-Chester disease and Langerhans cell histiocytosis. While historically, RDD was considered a benign self-limited condition, current data show MAPK/ERK pathway mutations in 30% to 50% of cases, indicative of a clonal process. Rosai-Dorfman disease was incorporated as a histiocytic neoplasm in the fifth edition of the World Health Organization classification of hematopoietic tumors and the International Consensus Classification.

METHODS

We discuss the diagnosis of RDD using 2 illustrative cases, interpretative challenges, and a diagnostic algorithm.

RESULTS

Rosai-Dorfman disease involves nodal and extranodal sites, including skin, sinuses, salivary gland, orbit, central nervous system, kidney, and bone. In a subset, RDD can coexist with other neoplasms (lymphomas, other histiocytosis) or autoimmune disease. Morphologically, RDD histiocytes are characterized by enlarged round to oval nuclei, distinct nucleoli, and voluminous cytoplasm with engulfment of inflammatory cells (emperipolesis). By immunohistochemistry, they express CD68, CD163 (majority), S100, OCT2, and cyclin D1. Appropriate use of ancillary studies is important to support the diagnosis of RDD while excluding other histiocytic neoplasms and reactive histiocytic proliferations.

CONCLUSIONS

Management of RDD is dependent on the extent of organ involvement and clinical symptoms. In patients who require therapy, next-generation sequencing is recommended to identify MAPK/ERK pathway mutations for targeted therapy.

The SLC29A3 variant, neutrophilic dermatosis, and hyperferritinemia imitate systemic juvenile idiopathic arthritis in a Saudi child: a case report

Genetic defects of SLC29A3 result in a wide range of syndromic histiocytosis that encompasses H syndrome. Patients with SLC29A3 variants typically have hyperpigmentation, hypertrichosis, hepatosplenomegaly, sensorineural hearing loss, diabetes mellitus, and hypogonadism. Herein, we identify a novel phenotype in a girl presenting with clinical and laboratory findings similar to systemic juvenile arthritis and hyperferritinemia. Exome sequencing identified a homozygous variant in SLC29A3 (NM_018344.5: c.707C>T [p.T236M]). Our patient did not show the cardinal features of the broad spectrum of SLC29A3-related disorders. She demonstrated remarkable improvement in her clinical and laboratory manifestations after starting interleukin-1 blockade (Anakinra). Recent research suggests that SLC29A3-related disorders are accompanied with autoinflammation and autoimmunity due to an overactive inflammasome pathway, which is most likely induced by mitochondrial and lysosomal dysfunction. Hence, our findings may expand the phenotypic features of the SLC29A3 variant. Patients with the SLC29A3 variant and systemic inflammation may benefit from interleukin-1 blockade as a therapeutic option.

OCT2 expression in histiocytoses

Diagnosis of histiocytosis can be difficult and one of the biggest challenges is to distinguish between reactive and neoplastic histiocytes on histology alone. Recently, OCT2 nuclear expression was reported in Rosai-Dorfman disease (RDD). Our purpose was to expand the testing of OCT2 on a broader variety of sporadic or H syndrome-related histiocytoses. Cases of histiocytoses were retrieved from the files of Ambroise Paré Pathology Department. All slides and molecular analyses were reviewed, and staining was completed with immunohistochemistry for OCT2. A total of 156 samples from different localizations were tested. Among sporadic cases, 52 patients had RDD, and 10 patients had mixed histiocytosis combining RDD with Erdheim Chester disease (ECD, n = 8), Langerhans cell histiocytosis (LCH, n = 2) or juvenile xanthogranuloma (JXG, n = 1). All these patients were positive for OCT2 in RDD characteristic histiocytes. Twenty-three patients had ECD and all but two (91% - 21/23) were negative for OCT2. By contrast, OCT2 was positive in 11/27 (41%) LCH and 6/16 (38%) JXG. Among the 10 samples of H syndrome-associated histiocytosis, 3 had typical RDD histology, 6 had unclassified histiocytosis, and one had mixed RDD-LCH; all were positive for OCT2. On 16 samples of granulomatous lymphadenitis, OCT2 was negative in epithelioid histiocytes. Our study shows that OCT2 has a sensitivity of 100% for RDD cases and mixed histiocytoses with an RDD component. It is negative in 92% of ECD but expressed in at least 38% of LCH, JXG, and C group histiocytoses. Finally, OCT2 is positive in all H syndrome-related histiocytoses, independent of their histology.

A case report of H-syndrome from Baghdad Medical City treated with tocilizumab

This case report presents the first H-syndrome rarity in Iraq, a 12-year-old female patient who was attending the Rheumatology out clinic for progressive hands joint deformities. She has a history of a multi-systemic collection of diseases with various clinical features that include beta thalassemia minor, sensorineural deafness, and celiac disease.

Diabetes Out-of-the-Box: Diabetes Mellitus and Impairment in Hearing and Vision

PURPOSEOF REVIEW

This review aims to provide an update on the etiologies of diabetes that are due to genetic disorders and that co-occur with impaired hearing or vision and to compare them. The potential mechanisms, including novel treatments, will be detailed.

RECENT FINDINGS

Wolfram syndrome, Kearns-Sayre syndrome, thiamine-responsive megaloblastic anemia, and maternally inherited diabetes and deafness are genetic disorders characterized by diabetes, impaired hearing, and vision. They differ in mode of inheritance, age at presentation, and the involvement of other organs; they are often misdiagnosed as type 1 or type 2 diabetes. Suspicion of a genetic diabetes syndrome should be raised when pancreatic autoantibodies are negative, other organs are involved, and family history includes diabetes. Correct diagnosis of the various syndromes is important for tailoring the most advanced treatment, preventing disease progression, and enabling proper genetic counseling.

Atypical comorbidities in a child considered to have type 1 diabetes led to the diagnosis of SLC29A3 spectrum disorder

INTRODUCTION

SLC29A3 spectrum disorder is an autosomal, recessively inherited, autoinflammatory, multisystem disorder characterized by distinctive cutaneous features, including hyperpigmentation or hypertrichosis, hepatosplenomegaly, hearing loss, cardiac anomalies, hypogonadism, short stature, and insulin-dependent diabetes.

CASE PRESENTATION

Herein, we report a 6-year-old boy who presented with features resembling type 1 diabetes mellitus, but his clinical course was complicated by IgA nephropathy, pure red cell aplasia, and recurrent febrile episodes. The patient was tested for the presence of pathogenic variants in 53 genes related to monogenic diabetes and found to be compound heterozygous for two SLC29A3 pathogenic variants (p. Arg386Gln and p. Leu298fs).

CONCLUSION

This case demonstrated that SLC29A3 spectrum disorder should be included in the differential diagnosis of diabetes with atypical comorbidities, even when the distinctive dermatological hallmarks of SLC29A3 spectrum disorder are entirely absent.

Novel Genomic Variants, Atypical Phenotypes and Evidence of a Digenic/Oligogenic Contribution to Disorders/Differences of Sex Development in a Large North African Cohort

In a majority of individuals with disorders/differences of sex development (DSD) a genetic etiology is often elusive. However, new genes causing DSD are routinely reported and using the unbiased genomic approaches, such as whole exome sequencing (WES) should result in an increased diagnostic yield. Here, we performed WES on a large cohort of 125 individuals all of Algerian origin, who presented with a wide range of DSD phenotypes. The study excluded individuals with congenital adrenal hypoplasia (CAH) or chromosomal DSD. Parental consanguinity was reported in 36% of individuals. The genetic etiology was established in 49.6% (62/125) individuals of the total cohort, which includes 42.2% (35/83) of 46, XY non-syndromic DSD and 69.2% (27/39) of 46, XY syndromic DSD. No pathogenic variants were identified in the 46, XX DSD cases (0/3). Variants in the AR, HSD17B3, NR5A1 and SRD5A2 genes were the most common causes of DSD. Other variants were identified in genes associated with congenital hypogonadotropic hypogonadism (CHH), including the CHD7 and PROKR2. Previously unreported pathogenic/likely pathogenic variants (n = 30) involving 25 different genes were identified in 22.4% of the cohort. Remarkably 11.5% of the 46, XY DSD group carried variants classified as pathogenic/likely pathogenic variant in more than one gene known to cause DSD. The data indicates that variants in PLXNA3, a candidate CHH gene, is unlikely to be involved in CHH. The data also suggest that NR2F2 variants may cause 46, XY DSD.

Inborn Errors of Nucleoside Transporter (NT)-Encoding Genes (SLC28 and SLC29)

The proper regulation of nucleotide pools is essential for all types of cellular functions and depends on de novo nucleotide biosynthesis, salvage, and degradation pathways. Despite the apparent essentiality of these processes, a significant number of rare diseases associated with mutations in genes encoding various enzymes of these pathways have been already identified, and others are likely yet to come. However, knowledge on genetic alterations impacting on nucleoside and nucleobase transporters is still limited. At this moment three gene-encoding nucleoside and nucleobase transporter proteins have been reported to be mutated in humans, SLC29A1, SLC29A3, and SLC28A1, impacting on the expression and function of ENT1, ENT3, and CNT1, respectively. ENT1 alterations determine Augustine-null blood type and cause ectopic calcification during aging. ENT3 deficiency translates into various clinical manifestations and syndromes, altogether listed in the OMIM catalog as histiocytosis-lymphoadenopathy plus syndrome (OMIM#602782). CNT1 deficiency causes uridine-cytidineuria (URCTU) (OMIM#618477), a unique type of pyrimidineuria with an as yet not well-known clinical impact. Increasing knowledge on the physiological, molecular and structural features of these transporter proteins is helping us to better understand the biological basis behind the biochemical and clinical manifestations caused by these deficiencies. Moreover, they also support the view that some metabolic compensation might occur in these disturbances, because they do not seem to significantly impact nucleotide homeostasis, but rather other biological events associated with particular subtypes of transporter proteins.

Unusual facial lesions in H syndrome

H Syndrome is a rare genodermatosis. It may include facial involvement such as: facial telangiectasia, both hypo- and hyperpigmented lesions, hirsutism, swollen cheeks due to subcutaneous infiltration and eczematous lesions. We describe a new facial phenotype with dermoscopic and histological features in the spectrum of non-Langerhans cell histiocytosis.

Case report of H-syndrome with a review from a rheumatological perspective

A woman in her 20s, symptomatic since the age of 4 with short stature, hearing loss, skin hyperpigmentation and induration over the medial aspect of the thigh, hypertrichosis, histiocytes on biopsy, lymphadenopathy, dilated scleral vessels, pancreatic exocrine deficiency, pericardial thickening, swelling of the eyelids and resistant retroperitoneal fibrosis. Whole-genome sequencing showed a mutation in SLC29A3, confirming 'H'-syndrome. She is on steroids and methotrexate. This case highlights the rheumatological mimics of this rare disorder.

H Syndrome: Report of The First Case in African Ethnicity

H syndrome is an autosomal recessive multisystemic disease with a very low prevalence rate, characterized by indurated cutaneous hyperpigmentation, hypertrichosis, and various systemic manifestations. The syndrome is caused by mutations in SLC29A3 gene on chromosome 10q23, encoding for human equilibrative transporter 3 (hENT3). So far, only 100-120 patients with H syndrome have been described in the literature, with predominance among Indian, North-American, and Arab ethnicities.

This case report describes the first one of H-syndrome rarities in African ethnicity, a 30-year-old Sudanese male misdiagnosed with rheumatoid arthritis. The patient exhibited more than 90% of the clinical characteristics of H syndrome including obesity, short stature, characteristic hyperpigmented, sclerotic cutaneous plaques with induration and hypertrichosis, inflammatory arthropathy, hallux valgus, flexion deformity of toes, exophthalmos, cardiac anomaly, hypogonadism, and splenomegaly and characteristic histologic findings of dermal fibrosis, histiocytosis, lymphoid aggregation, and vascular proliferation.

H syndrome is an extremely rare autoinflammatory condition that has a complex constellation of pleiotropic manifestations with multisystemic involvement. And while further identification and better pathophysiological understanding of H syndrome are needed, physicians worldwide should be vigilant about the overlapping features of H syndrome with many other rheumatological, cutaneous, and genetic diseases.

The application of precision medicine in monogenic diabetes

INTRODUCTION

Monogenic diabetes, a form of diabetes mellitus, is caused by a mutation in a single gene and may account for 1-2% of all clinical forms of diabetes. To date, more than 40 loci have been associated with either isolated or syndromic monogenic diabetes.

AREAS COVERED

While the request of a genetic test is mandatory for cases with diabetes onset in the first 6 months of life, a decision may be difficult for childhood or adolescent diabetes. In an effort to assist the clinician in this task, we have grouped monogenic diabetes genes according to the age of onset (or incidental discovery) of hyperglycemia and described the additional clinical features found in syndromic diabetes. The therapeutic options available are reviewed.

EXPERT OPINION

Technical improvements in DNA sequencing allow for rapid, simultaneous analysis of all genes involved in monogenic diabetes, progressively shrinking the area of unsolved cases. However, the complexity of the analysis of genetic data requires close cooperation between the geneticist and the diabetologist, who should play a proactive role by providing a detailed clinical phenotype that might match a specific disease gene.

Review of the current literature on H syndrome treatment

H syndrome is a systemic inherited autosomal recessive histiocytosis, with characteristic cutaneous findings accompanying systemic manifestations and a most common genetic mutation (OMIM 612391) as SLC29A3. The term “H Syndrome” is representative of presentation with hyperpigmentation, hypertrichosis, hepatosplenomegaly, heart anomalies, hearing loss, hypogonadism, low height, and, occasionally, hyperglycemia. H syndrome is new and growing entity in medicine. This syndrome is not specific to a region or a nationality. There are very few treatment experiences on H Syndrome patients and most of them are unsatisfactory apart from hypertrichosis, which is able to treat almost permanently by hair removal lasers. Latest findings suggest that there is possibility of prevention of short stature or other cutaneous or systemic complications in this syndrome with earlier diagnosis and treatment. We searched Medline, Scopus, Web of Sciences, and Google Scholar, up to now and reviewed previous published papers with emphasis on treatment methods and its effects on certain common symptoms.

Audiological findings of a patient with H syndrome: case report

Background

H syndrome is an autosomal recessive disorder caused by mutations in SLC29A3. Hyperpigmentation, hypertrichosis, hyperglycemia, and hearing loss are some characteristics of this disorder, and it has a prevalence of < 1/1000. The aim of this report is to spread awareness among otologists, audiologists, and pediatricians about this syndrome and its audiological features.

Case presentation

An 8-year-old male with a diagnosed H syndrome registered to our clinic with a complaint of hearing loss. The patient was diagnosed with hearing loss in a different clinic using only the air-conducted click auditory brainstem response test which showed wave V at 60 dB nHL for the right ear and at 80 dB nHL for the left ear. The initially performed pure tone audiometry (PTA) test in our clinic revealed a bilateral asymmetric hearing loss with a moderate sensorineural hearing loss in the right ear and a profound mixed hearing loss in the left ear. The performed air conducted click auditory brainstem response (ABR) result showed wave V at 55 dB nHL for the right ear and at 70 dB nHL for the left ear. Then, the repeated PTA test revealed a mild-severe sensorineural sloping hearing loss in the right ear and a severe sensorineural hearing loss in the left ear.

Conclusion

Although hearing thresholds in H syndrome could be within normal limits in some patients, sensorineural hearing loss is an important characteristic feature for this syndrome. Sensorineural hearing loss could be progressive or of sudden onset and ranges from mild to profound. Thus, it must be taken into consideration to apply the audiological follow-up regularly and paying attention to the patient’s complaints; also, a regular follow-up for language development of children with H syndrome and for the hearing aids is advised.

Histiocytic Neoplasms, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

Histiocytic neoplasms are rare hematologic disorders accounting for less than 1% of cancers of the soft tissue and lymph nodes. Clinical presentation and prognosis of these disorders can be highly variable, leading to challenges for diagnosis and optimal management of these patients. Treatment often consists of systemic therapy, and recent studies support use of targeted therapies for patients with these disorders. Observation ("watch and wait") may be sufficient for select patients with mild disease. These NCCN Guidelines for Histiocytic Neoplasms include recommendations for diagnosis and treatment of adults with the most common histiocytic disorders: Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease.

Dermatologic manifestations of pediatric cardiovascular diseases: Skin as a reflection of the heart

Cutaneous disease can often be an initial clue of an underlying cardiovascular disease. Many congenital conditions (ie, Noonan syndrome with multiple lentigines, Carney complex, and Fabry disease) and acquired conditions may present initially with specific cutaneous features that should prompt clinicians to conduct a full cardiac workup. Given the extensive number of conditions with both cardiovascular and cutaneous findings, this review will focus on diseases with cardiocutaneous pathology with hopes of raising clinician awareness of these associations to decrease morbidity and mortality, as several of these diseases often result in fatal outcomes.

Phenotypic intrafamilial variability including H syndrome and Rosai-Dorfman disease associated with the same c.1088G > A mutation in the SLC29A3 gene

Background

Mutations in the SLC29A3 gene, which encodes the nucleoside transporter hENT3, have been implicated in syndromic forms of histiocytosis including H syndrome, pigmented hypertrichosis with insulin-dependent diabetes, Faisalabad histiocytosis and Familial Rosai–Dorfman disease (RDD). Herein, we report five new patients from a single family who present with phenotypes that associate features of H syndrome and Familial Rosai–Dorfman disease.

Methods

We investigated the clinical, biochemical, histopathological and molecular findings in five Tunisian family members' diagnosed with Familial RDD and/or H syndrome. The solute carrier family 29 (nucleoside transporters), member 3 (SLC29A3) gene was screened for molecular diagnosis using direct Sanger sequencing.

Results

Genetic analysis of all affected individuals revealed a previously reported missense mutation c.1088 G > A [p.Arg363Gln] in exon 6 of the SLC29A3 gene. Four affected members presented with clinical features consistent with the classical H syndrome phenotype. While their cousin’s features were in keeping with Familial Rosai–Dorfman disease diagnosis with a previously undescribed cutaneous RDD presenting as erythematous nodular plaques on the face. This report underlines the clinical variability of SLC29A3 disorders even with an identical mutation in the same family.

Conclusion

We report a rare event of 5 Tunisian family members' found to be homozygous for SLC29A3 gene mutations but showing a different phenotype severity. Our study reveals that despite a single mutation, the clinical expression of the SLC29A3 disorders may be significantly heterogeneous suggesting a poor genotype–phenotype correlation for the disease.

H syndrome: A review of treatment options and a hypothesis of phenotypic variability

H syndrome is a rare autosomal recessive disorder with clinical features comprising: hyperpigmentation, hypertrichosis, hearing loss, heart anomalies, low height, hypogonadism and hepatosplenomegaly. H syndrome results from loss-of-function mutations in SLC29A3 which leads to abnormal proliferation and function of histiocytes. Herein, we discuss the considerable phenotypic heterogeneity detected in a consanguineous Egyptian family comprising of four affected siblings, two of which are monozygotic twin and the possible therapeutics. The phenotypic variability may be attributed to the role of histiocytes in the tissue response to injury. Such variable expressivity of H syndrome renders the diagnosis challenging and delays the management. The different treatment approaches used for this rare entity are reviewed.

Approach to inherited hypertrichosis: A brief review

Hypertrichosis refers to the growth of hair, of an excessive amount and thickness, on any part of the body. It must be distinguished from hirsutism which is characterized by excess growth of hair in androgen-dependent areas on the upper lip, chin, chest, linea alba, thigh and axilla. Hypertrichosis may be localized or generalized, and congenital or acquired. Excess hair growth has a psychological impact on the child as well as the parents due to the cosmetic disfigurement it produces. Current treatment options are limited and not wholly satisfactory. Treatment should be customized according to the area, nature and amount of hair growth, age of the patient and personal preferences. In addition, when hypertrichosis occurs as a component of a syndrome, multidisciplinary management is required to address the associated systemic features. A detailed review of inherited generalized hypertrichosis is presented here with emphasis on clinical clues to identifying complex syndromes with multisystem involvement.

Histiocytosis

Histiocytoses constitute a heterogeneous group of rare disorders, characterised by infiltration of almost any organ by myeloid cells with diverse macrophage or dendritic cell phenotypes. Histiocytoses can start at any age. Diagnosis is based on histology in combination with appropriate clinical and radiological findings. The low incidence and broad spectrum of clinical manifestations often leads to diagnostic delay, especially for adults. In most cases, biopsy specimens infiltrated by histiocytes have somatic mutations in genes activating the MAP kinase cell-signalling pathway. These mutations might also be present in blood cells and haematopoietic progenitors of patients with multisystem disease. A comprehensive range of investigations and molecular typing are essential to accurately predict prognosis, which can vary from spontaneous resolution to life-threatening disseminated disease. Targeted therapies with BRAF or MEK inhibitors have revolutionised salvage treatment. However, the type and duration of treatment are still debated, and the prevention of neurological sequelae remains a crucial issue.

Patient with H syndrome, cardiogenic shock, multiorgan infiltration, and digital ischemia

BACKGROUND

H syndrome (HS) is a rare autoinflammatory disease caused by a mutation in the solute carrier family 29, member 3 (SCL29A3) gene. It has a variable clinical presentation and little phenotype-genotype correlation. The pathognomonic sign of HS is cutaneous hyperpigmentation located mainly in the inner thighs and often accompanied by other systemic manifestations. Improvement after tocilizumab treatment has been reported in a few patients with HS. We report the first patient with HS who presented cardiogenic shock, multiorgan infiltration, and digital ischemia.

CASE PRESENTATION

8-year-old boy born to consanguineous parents of Moroccan origin who was admitted to the intensive care unit during the Coronavirus Disease-2019 (COVID-19) pandemic with tachypnoea, tachycardia, and oliguria. Echocardiography showed dilated cardiomyopathy and severe systolic dysfunction compatible with cardiogenic shock. Additionally, he presented with multiple organ dysfunction syndrome. SARS-CoV-2 polymerase chain reaction (PCR) and antibody detection by chromatographic immunoassay were negative. A previously ordered gene panel for pre-existing sensorineural hearing loss showed a pathological mutation in the SCL29A3 gene compatible with H syndrome. Computed tomography scan revealed extensive alveolar infiltrates in the lungs and multiple poor defined hypodense lesions in liver, spleen, and kidneys; adenopathy; and cardiomegaly with left ventricle subendocardial nodules. Invasive mechanical ventilation, broad antibiotic and antifungal coverage showed no significant response. Therefore, Tocilizumab as compassionate use together with pulsed intravenous methylprednisolone was initiated. Improvement was impressive leading to normalization of inflammation markers, liver and kidney function, and stabilising heart function. Two weeks later, he was discharged and has been clinically well since then on two weekly administration of Tocilizumab.

CONCLUSIONS

We report the most severe disease course produced by HS described so far in the literature. Our patient's manifestations included uncommon, new complications such as acute heart failure with severe systolic dysfunction, multi-organ cell infiltrate, and digital ischemia. Most of the clinical symptoms of our patient could have been explained by SARS-CoV-2, demonstrating the importance of a detailed differential diagnosis to ensure optimal treatment. Although the mechanism of autoinflammation of HS remains uncertain, the good response of our patient to Tocilizumab makes a case for the important role of IL-6 in this syndrome and for considering Tocilizumab as a first-line treatment, at least in severely affected patients.

'H-syndrome': a multisystem genetic disorder with cutaneous clues

We present a case of a 25-year-old man who came to our Endocrine Clinic for evaluation of short stature. He had a history of sensorineural hearing loss, hypertrichosis and hyperpigmentation with the thickening of the skin below the hip, gynecomastia and autoimmune haemolytic anaemia. Investigations showed that he had hypergonadotropic hypogonadism. His phenotype was consistent with that of a rare autosomal recessive genodermatosis of 'H-syndrome'. The diagnosis was confirmed by genetic analysis using next-generation sequencing which showed a homozygous mutation in the SLC29A3 gene (variant: c.1330G>T (p.Glu444Ter)) which was confirmed by Sanger sequencing. This is a rare syndrome with around 100 cases reported in world literature. Though the skin manifestations are pathognomonic of the H-syndrome, it has myriad presentations like short stature, insulin-dependent diabetes mellitus, hypogonadism, hypothyroidism, dyslipidaemia, cardiac anomalies and sensorineural hearing loss. We report this case to highlight the constellation of features of this rare syndrome and bring awareness among the physicians to be vigilant about this syndrome.

Multimodality imaging of constrictive pericarditis in H syndrome

This is the first report of constrictive pericarditis (CP) in a 16-year-old boy with H syndrome with pericardial involvement predominantly over the right ventricle with favorable response to anti-inflammatory treatment. H syndrome, first reported in 2008, is a new auto-inflammatory syndrome with multiorgan involvement due to mutation in the SLC29A3 gene. We described the echocardiographic characteristics of asymmetric pericardial involvement and presented the cardiac computed tomography angiographic and magnetic resonance imaging findings. We reviewed the echocardiographic signs of CP, introduced tricuspid E/A respiratory alternans as a novel echocardiographic sign of right ventricular dominant CP, and explained the underlying mechanism.

Pseudo-Meigs' Syndrome in Tunisian H Syndrome Female Patient: First Case Reported

H syndrome is an extremely rare autosomal recessive affection caused by biallelic mutations in the SLC29A3 gene encoding the human equilibrative nucleoside transporter hENT3. The hallmark signs are cutaneous consisting of hyperpigmentation and hypertrichosis patches. Besides, associated systemic manifestations are highly various reflecting phenotypic pleiotropism. Herein, we report a first case of pseudo-Meigs’ syndrome occurring in a young Tunisian H syndrome diagnosed patient with a novel homozygous frameshift mutation in exon 2 of the SLC29A3 gene: p.S15Pfs*86 inducing a premature stop codon. The patient developed ascites associated with left ovarian mass and she underwent surgery. After tumor resection, ascites disappeared rapidly. Histological examination showed serous cystadenoma of the ovary orienting the diagnosis towards pseudo-Meigs’ syndrome.

Genetic disorders with symptoms mimicking rheumatologic diseases: A single-center retrospective study

Musculoskeletal symptoms may be due to noninflammatory causes, including genetic disorders. We aimed to examine the final genetic diagnosis in patients who presented with musculoskeletal complaints to the rheumatology department. Patients who presented to the Department of Pediatric Rheumatology and were referred to the pediatric genetic department between January 2015 and May 2019 were evaluated retrospectively. A total of 60 patients, 19 boys (31.66%), with a mean age of 12.46 ± 1.41 years were included in the study. The total consanguinity rate was 25%. The most common (29.5%) cause of referral to the pediatric genetic department was the presence of skeletal anomalies (such as camptodactyly, clinodactyly, and short stature) with accompanying joint findings. Approximately one-third of the patients (n: 19) were diagnosed and followed up by the pediatric genetics department. The diagnoses of patients were as follows: camptodactyly, arthropathy, coxa vara, and pericarditis (CACP) syndrome (n: 3); trichorhinophalangeal syndrome (n: 1); progressive pseudorheumatoid dysplasia (n: 2); LIG4 syndrome (n: 1); H syndrome (n: 1); spondyloenchondrodysplasia (SPENCD) (n: 3); and nonspecific connective tissue disorders (n: 8). In the differential diagnosis of patients who are referred to the Department of Pediatric Rheumatology with complaints of the musculoskeletal system, genetic disorders should also be considered.

Glomerular involvement in children with H syndrome

BACKGROUND

H syndrome is a multisystem inflammatory disease caused by mutations in the SLC29A3 gene (OMIM #602782). The protein product, hENT3, is a nucleoside transporter essential for DNA salvage synthesis. Clinical manifestations are hyperpigmentation, hypertrichosis, hepatosplenomegaly, hearing loss, heart anomalies, hypogonadism, short stature, skeletal deformities, and diabetes mellitus. Laboratory findings are consistent with inflammatory processes. Structural kidney anomalies have been described in 6% of patients.

CASE REPORTS

Three family members with genetically diagnosed H syndrome (c.1279G>A, p.Gly427Ser). Two of them presented with hypoalbuminemia and nephrotic range proteinuria. Kidney ultrasound was normal. Kidney biopsy performed in one patient presenting with generalized peripheral pitting edema revealed membranous nephropathy. Different treatments including ACE inhibitors, corticosteroids, and immunomodulatory agents failed to improve the clinical outcome.

CONCLUSIONS

Generalized peripheral pitting edema and glomerulopathy broaden the clinical spectrum of H syndrome. Periodic bloodwork and urinalysis are recommended.

Identification of Critical Transcriptomic Signaling Pathways in Patients with H Syndrome and Rosai-Dorfman Disease

Biallelic mutations in SLC29A3 cause histiocytosis-lymphadenopathy plus syndrome, also known as H syndrome (HS). HS is a complex disorder, with ~ 25% of patients developing autoinflammatory complications consisting of unexplained fevers, persistently elevated inflammatory markers, and unusual lymphadenopathies, with infiltrating CD68⁺, S100⁺, and CD1a^- histiocytes, resembling the immunophenotype found in Rosai-Dorfman disease (RDD). We investigated the transcriptomic profiles of monocytes, non-activated (M0), classically activated (M1), and alternatively activated macrophages (M2) in two patients with HS, one without autoinflammatory (HS1) and one with autoinflammatory complications (HS2). RNA sequencing revealed a dysregulated transcriptomic profile in both HS patients compared to healthy controls (HC). HS2, when compared to HS1, had several differentially expressed genes, including genes associated with lymphocytic-histiocytic predominance (e.g. NINL) and chronic immune activation (e.g. B2M). The transcriptomic and cytokine profiles of HS patients were comparable to patients with SAID with high levels of TNF. SERPINA1 gene expression was found to be upregulated in all patients studied. Moreover, higher levels of IFNγ were found in the serum of both HS patients when compared to HC. Gene ontology (GO) enrichment analysis of the DEGs in HS patients revealed the terms "type I IFN," "IFNγ signaling pathway," and "immune responses" as the top 3 most significant terms for monocytes. Gene expression analysis of lymph node biopsies from sporadic and H syndrome-associated RDD suggests common underlying pathological process. In conclusion, monocytes and macrophages from both HS patients showed transcriptomic profiles similar to SAIDs and also uniquely upregulated IFNγ signature. These findings may help find better therapeutic options for this rare disorder.

Inherited disorders of lysosomal membrane transporters

Disorders caused by defects in lysosomal membrane transporters form a distinct subgroup of lysosomal storage disorders (LSDs). To date, defects in only 10 lysosomal membrane transporters have been associated with inherited disorders. The clinical presentations of these diseases resemble the phenotypes of other LSDs; they are heterogeneous and often present in children with neurodegenerative manifestations. However, for pathomechanistic and therapeutic studies, lysosomal membrane transport defects should be distinguished from LSDs caused by defective hydrolytic enzymes. The involved proteins differ in function, localization, and lysosomal targeting, and the diseases themselves differ in their stored material and therapeutic approaches. We provide an overview of the small group of disorders of lysosomal membrane transporters, emphasizing discovery, pathomechanism, clinical features, diagnostic methods and therapeutic aspects. We discuss common aspects of lysosomal membrane transporter defects that can provide the basis for preclinical research into these disorders.

H syndrome with a novel homozygous SLC29A3 mutation in two sisters

H syndrome (OMIM 602782) is a recently defined autosomal recessive genodermatosis. Cutaneous findings of H syndrome include hyperpigmentation, hypertrichosis, and induration, while hearing loss, heart anomalies, hepatomegaly, hypogonadism, hyperglycemia (diabetes mellitus), low height (short stature), hallux valgus (flexion contractures), and hematological abnormalities are the extracutaneous abnormalities. We report a novel homozygous missense mutation, c.416T > C p.(Leu139Pro), in the SLC29A3 (NM_001174098.1) gene in two sisters with H syndrome presenting with different phenotypes.

H Syndrome retrospectively diagnosed: The importance of recognizing cutaneous signs

We present a case of a retrospectively diagnosed H syndrome in a man who died of a probable heart infarction. We highlight the importance of recognizing cutaneous hallmarks of this syndrome for better clinical management and prevention.

Rosai-Dorfman disease: an overview

CONTEXT

Rosai-Dorfman disease is an uncommon histiocytic disorder most frequently presenting as bilateral cervical lymphadenopathy in children and young adults. Extranodal disease occurs in a significant proportion of patients. It has been recently classified as part of the 'R group' of histiocytoses by the Histiocyte Society in 2016. Cutaneous Rosai-Dorfman disease is regarded as a separate disease entity that falls into the 'C group' of histiocytoses according to this classification system. The pathogenesis was previously poorly understood; however, recent evidence demonstrating clonality in a subset of cases raises the possibility of a neoplastic process. A possible association with IgG4-related disease remains controversial.

OBJECTIVES

To provide a comprehensive review of Rosai-Dorfman disease, including nodal, extranodal and cutaneous forms, with a particular emphasis on new insights into the possible clonal nature of the disease; to discuss the recently revised classification of the histiocytoses by the Histiocyte Society; and to summarise the findings from the literature regarding the controversial association with IgG4-related disease.

DATA SOURCES

This review is based on published peer-reviewed English literature.

CONCLUSIONS

Classic Rosai-Dorfman disease, which may be sporadic or familial, is considered a separate entity from cutaneous disease, which is reflected in the revised classification of histiocytoses. An increase in IgG4-positive plasma cells may be seen in Rosai-Dorfman disease. This finding in isolation is of limited significance and should be interpreted with caution. Studies investigating the molecular profile of the disease show that in at least a subset of cases the disease is a clonal process. The classification of Rosai-Dorfman disease is therefore likely to change as our understanding of the aetiopathogenesis evolves.