A novel insight into the pathophysiology of autoimmune hepatitis: An immune activator mutation in the FLT3 receptor

Autoimmune hepatitis (AIH) is a chronic progressive autoimmune liver disease characterized by hypergammaglobulinemia, interface hepatitis, female preponderance and presence of autoantibodies in most patients. The presence of HLA-DR3/DR4 and functional impairments in regulatory T cells are associated with AIH. However, AIH is a multifactorial complex disease. In this report, we present a case of a seronegative AIH girl with chronic hepatitis, hyper-IgE, perforating nodular dermatitis and sheer eosinophilia. To re-evaluate the diagnosis, whole exon sequencing was performed. We determined that the patient has the ancestral haplotype A1-B8-DR3 associated with autoimmunity. More importantly, we found an undocumented point mutation (Ala627Thr) of the FMS-like-tyrosine 3 kinase (FLT3) receptor. This FLT3 receptor gain-of-function mutation is associated with the activation of the mammalian target of rapamycin (mTOR) instigating dendritic cell activation. Furthermore, a loss-of-function mutation in the melanocortin-3 receptor (MC3R) gene paramount in inhibiting IL4 was detected. The constellation of these immune deregulatory factors may have propagated auto-aggression of the liver causing chronic hepatitis with AIH features. Albeit, the seronegativity with eosinophilia and hyper-IgE let us hypothesize that the pathognomonic mechanisms, in this case, diverts from classical AIH pathophysiology. As mTOR is constitutively activated, mTOR inhibitors may be used to treat AIH and dermatitis

“Double Hit” Homozygous Mutations for Two Different Rare Inborn Errors of Metabolism: A Burden for Countries with High Prevalences of Consangineous Marriages

Inborn errors of metabolism comprise a broad range of genetic diseases of which most are inherited in an autosomal recessive manner. Although being rare, there is a significant increase in their rate especially in countries where consanguineous marriages are performed. Isovaleric aciduria is an organic aciduria characterized by abnormal leucine metabolism resulting from a deficiency in the enzyme isovaleryl-CoA dehydrogenase. Niemann-Pick disease Type C is a rare autosomal recessive inherited disorder involving the intracellular transport of endocytosed cholesterol with sequestration of unesterified cholesterol in lysosomes and late endosomes. Both of these disorders are rarely encountered inborn errors of metabolism. We report a case of a boy with marked jaundice and hepatosplenomegaly, who was later diagnosed as isovaleric aciduria and Niemann-Pick disease Type C concomitantly. The diagnoses were proven by genetic analyses. A novel mutation for Niemann-Pick Type C has also been defined in this case report

Sporadic Nonautoimmune Neonatal Hyperthyroidism Due to A623V Germline Mutation in the Thyrotropin Receptor Gene

Neonatal hyperthyroidism is a rare disorder and occurs in two forms. An autoimmune form is associated with maternal Graves' disease, resulting from transplacental passage of maternal thyroid−stimulating antibodies and a nonautoimmune form is caused by gain of function mutations in the thyrotropin receptor (TSHR) gene. Thyrotoxicosis caused by germline mutations in the TSHR gene may lead to a variety of clinical consequences. To date, 55 activating mutations of the TSHR gene have been documented. Fourteen cases with sporadic activating TSHR germline mutations have been described. Here we report a male infant with nonautoimmune hyperthyroidism due to an activating germline TSHR mutation (A623V), whose clinical picture started in the newborn period with severe hyperthyroidism. His parents did not have the same mutation. This mutation had been previously detected as a somatic mutation in patients with toxic adenomas. This is the first report of a sporadic case of nonautoimmune congenital hyperthyroidism associated with A623V mutation

Siblings with Ethylmalonic Encephalopathy: Case Report

Deficiency of mitochondrial sulfur dioxygenase (ETHE1) causes a rare inborn error of metabolism, ethylmalonic encephalopathy, which is characterized by early-onset encephalopathy, chronic hemorrhagic diarrhea, recurrent petechiae, orthostatic acrocyanosis, defective cytochrome C oxidase because of hydrogen sulfide accumulation and death in the first years of life. Biochemical hallmarks of the disease are high level of lactate, C4-C5-acylcarnitines in blood and markedly elevated urinary excretion of methylsuccinic and ethylmalonic acids. We report on two siblings who were admitted to a pediatric metabolic unit with acrocyanosis, chronic diarrhea and psychomotor retardation later diagnosed as ethylmalonic encephalopathy. Molecular analyses revealed a homozygous for p.R163Q (c.488 G>A) mutation in ETHE1 gene

A 6-Month-Old Boy with Reddish, Scaly Skin: Netherton Syndrome

Typical features of Netherton syndrome are congenital ichthyosiform erythroderma, atopic diathesis and trichorrhexis nodosa. Here in this report, we present a case with congenital ichthyosis with atopy presenting later. We wanted to discuss the importance of whole exome sequencing to diagnose the atypical presentations of common syndromes

Bi-allelic loss-of-function OBSCN variants predispose individuals to severe recurrent rhabdomyolysis

Rhabdomyolysis is the acute breakdown of skeletal myofibres in response to an initiating factor, most commonly toxins and over exertion. A variety of genetic disorders predispose to rhabdomyolysis through different pathogenic mechanisms, particularly in patients with recurrent episodes. However, most cases remain without a genetic diagnosis. Here we present six patients who presented with severe and recurrent rhabdomyolysis, usually with onset in the teenage years; other features included a history of myalgia and muscle cramps. We identified 10 bi-allelic loss-of-function variants in the gene encoding obscurin (OBSCN) predisposing individuals to recurrent rhabdomyolysis. We show reduced expression of OBSCN and loss of obscurin protein in patient muscle. Obscurin is proposed to be involved in sarcoplasmic reticulum function and Ca2+ handling. Patient cultured myoblasts appear more susceptible to starvation as evidenced by a greater decreased in sarcoplasmic reticulum Ca2+ content compared to control myoblasts. This likely reflects a lower efficiency when pumping Ca2+ back into the sarcoplasmic reticulum and/or a decrease in Ca2+ sarcoplasmic reticulum storage ability when metabolism is diminished. OSBCN variants have previously been associated with cardiomyopathies. None of the patients presented with a cardiomyopathy and cardiac examinations were normal in all cases in which cardiac function was assessed. There was also no history of cardiomyopathy in first degree relatives, in particular in any of the carrier parents. This cohort is relatively young, thus follow-up studies and the identification of additional cases with bi-allelic null OBSCN variants will further delineate OBSCN-related disease and the clinical course of disease. Cabrera-Serrano et al. show that biallelic loss-of-function variants in the gene encoding obscurin (OBSCN) predispose individuals to recurrent and severe episodes of rhabdomyolysis, typically with onset in the teenage years.Peer reviewe

Mutations in SLC29A3, Encoding an Equilibrative Nucleoside Transporter ENT3, Cause a Familial Histiocytosis Syndrome (Faisalabad Histiocytosis) and Familial Rosai-Dorfman Disease

The histiocytoses are a heterogeneous group of disorders characterised by an excessive number of histiocytes. In most cases the pathophysiology is unclear and treatment is nonspecific. Faisalabad histiocytosis (FHC) (MIM 602782) has been classed as an autosomal recessively inherited form of histiocytosis with similarities to Rosai-Dorfman disease (RDD) (also known as sinus histiocytosis with massive lymphadenopathy (SHML)). To elucidate the molecular basis of FHC, we performed autozygosity mapping studies in a large consanguineous family and identified a novel locus at chromosome 10q22.1. Mutation analysis of candidate genes within the target interval identified biallelic germline mutations in SLC29A3 in the FHC kindred and in two families reported to have familial RDD. Analysis of SLC29A3 expression during mouse embryogenesis revealed widespread expression by e14.5 with prominent expression in the central nervous system, eye, inner ear, and epithelial tissues including the gastrointestinal tract. SLC29A3 encodes an intracellular equilibrative nucleoside transporter (hENT3) with affinity for adenosine. Recently germline mutations in SLC29A3 were also described in two rare autosomal recessive disorders with overlapping phenotypes: (a) H syndrome (MIM 612391) that is characterised by cutaneous hyperpigmentation and hypertrichosis, hepatomegaly, heart anomalies, hearing loss, and hypogonadism; and (b) PHID (pigmented hypertrichosis with insulin-dependent diabetes mellitus) syndrome. Our findings suggest that a variety of clinical diagnoses (H and PHID syndromes, FHC, and familial RDD) can be included in a new diagnostic category of SLC29A3 spectrum disorder

An infant with glutaric aciduria type IIc diagnosed with a novel mutation

Glutaric aciduria type II is a rare inborn error of metabolism. The clinical picture is highly variable with symptoms ranging from acute metabolic decompensations to chronic, mainly muscular problems or even asymptomatic cases. Herein we described a 7-month-old female patient presented with respiratory failure and diagnosed with glutaric aciduria type II via whole exome sequencing that exhibited one known and a novel mutation. Her blood and urine analyses were all normal. After the diagnosis, dramatic and sustained improvement on a low-fat, low-protein, and high-carbohydrate diet supplemented with oral riboflavin and carnitine was determined. In especially hypotonic patients with unknown etiologies, though the blood and urine analyses are normal, glutaric aciduria type II should also be kept in mind and genetic tests may be required for the diagnosis