Protein-elongating mutations in MYH11 are implicated in a dominantly inherited smooth muscle dysmotility syndrome with severe esophageal, gastric, and intestinal disease.

Gastrointestinal motility disorders include a spectrum of mild to severe clinical phenotypes that are caused by smooth muscle dysfunction. We investigated the genetic etiology of severe esophageal, gastric, and colonic dysmotility in two unrelated families with autosomal dominant disease presentation. Using exome sequencing, we identified a 2 base pair insertion at the end of the myosin heavy chain 11 (MYH11) gene in all affected members of Family 1 [NM_001040113:c.5819_5820insCA(p.Gln1941Asnfs*91)] and a 1 base pair deletion at the same genetic locus in Proband 2 [NM_001040113:c.5819del(p.Pro1940Hisfs*91)]. Both variants are predicted to result in a similarly elongated protein product. Heterozygous dominant negative MYH11 pathogenic variants have been associated with thoracic aortic aneurysm and dissection while biallelic null alleles have been associated with megacystis microcolon intestinal hypoperistalsis syndrome. This report highlights heterozygous protein-elongating MYH11 variants affecting the SM2 isoforms of MYH11 as a cause for severe gastrointestinal dysmotility, and we hypothesize that the mechanistic pathogenesis of this disease, dominant hypercontractile loss-of-function, is distinct from those implicated in other diseases involving MYH11 dysfunction.

Successful liver transplantation in mitochondrial neurogastrointestinal encephalomyopathy (MNGIE).

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a fatal disorder characterized by progressive gastrointestinal dysmotility, peripheral neuropathy, leukoencephalopathy, skeletal myopathy, ophthalmoparesis, and ptosis. MNGIE stems from deficient thymidine phosphorylase activity (TP) leading to toxic elevations of plasma thymidine. Hematopoietic stem cell transplant (HSCT) restores TP activity and halts disease progression but has high transplant-related morbidity and mortality. Liver transplant (LT) was reported to restore TP activity in two adult MNGIE patients. We report successful LT in four additional MNGIE patients, including a pediatric patient. Our patients were diagnosed between ages 14 months and 36 years with elevated thymidine levels and biallelic pathogenic variants in TYMP. Two patients presented with progressive gastrointestinal dysmotility, and three demonstrated progressive peripheral neuropathy with two suffering limitations in ambulation. Two patients, including the child, had liver dysfunction and cirrhosis. Following LT, thymidine levels nearly normalized in all four patients and remained low for the duration of follow-up. Disease symptoms stabilized in all patients, with some manifesting improvements, including intestinal function. No patient died, and LT appeared to have a more favorable safety profile than HSCT, especially when liver disease is present. Follow-up studies will need to document the long-term impact of this new approach on disease outcome. Take Home Message: Liver transplantation is effective in stabilizing symptoms and nearly normalizing thymidine levels in patients with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) and may have an improved safety profile over hematopoietic stem cell transplant.

A girl with MIRAGE syndrome who developed steroid-resistant nephrotic syndrome: a case report.

BACKGROUND: MIRAGE syndrome is a recently discovered rare genetic disease characterized by myelodysplasia (M), infection (I), growth restriction (R), adrenal hypoplasia (A), genital phenotypes (G), and enteropathy (E), caused by a gain-of-function mutation in the SAMD9 gene. We encountered a girl with molecularly-confirmed MIRAGE syndrome who developed steroid-resistant nephrotic syndrome. CASE PRESENTATION: She was born at 33 weeks gestational age with a birth weight of 1064 g. She showed growth failure, mild developmental delays, intractable enteropathy and recurrent pneumonia. She was diagnosed as MIRAGE syndrome by whole exome sequencing and a novel SAMD9 variant (c.4615 T > A, p.Leu1539Ile) was identified at age four. Biopsied skin fibroblast cells showed changes in the endosome system that are characteristic of MIRAGE syndrome, supporting the genetic diagnosis. Proteinuria was noted at age one, following nephrotic syndrome at age five. A renal biopsy showed focal segmental glomerulosclerosis (FSGS) with immune deposits. Steroid treatment was ineffective. Because we speculated that her nephrosis was a result of genetic FSGS, we decided not to introduce immunosuppressive agents and instead started enalapril to reduce proteinuria. Although her proteinuria persisted, her renal function was normal at age eight. CONCLUSIONS: This is the first detailed report of a MIRAGE syndrome patient with nephrotic syndrome. Because patients with MIRAGE syndrome have structural abnormalities in the endosomal system, we speculate that dysfunction of endocytosis in podocytes might be a possible mechanism for proteinuria.

Persistent mechanical stretch-induced calcium overload and MAPK signal activation contributed to SCF reduction in colonic smooth muscle in vivo and in vitro.

Gastrointestinal (GI) distention is a common pathological characteristic in most GI motility disorders (GMDs), however, their detail mechanism remains unknown. In this study, we focused on Ca2+ overload of smooth muscle, which is an early intracellular reaction to stretch, and its downstream MAPK signaling and also reduction of SCF in vivo and in vitro. We successfully established colonic dilation mouse model by keeping incomplete colon obstruction for 8 days. The results showed that persistent colonic dilation clearly induced Ca2+ overload and activated all the three MAPK family members including JNK, ERK and p38 in smooth muscle tissues. Similar results were obtained from dilated colon of patients with Hirschsprung's disease and stretched primary mouse colonic smooth muscle cells (SMCs). Furthermore, we demonstrated that persistent stretch-induced Ca2+ overload was originated from extracellular Ca2+ influx and endoplasmic reticulum (ER) Ca2+ release identified by treating with different Ca2+ channel blockers, and was responsible for the persistent activation of MAPK signaling and SCF reduction in colonic SMCs. Our results suggested that Ca2+ overload caused by smooth muscle stretch led to persistent activation of MAPK signaling which might contribute to the decrease of SCF and development of the GMDs.

Involvement of Cerebellum in Leigh Syndrome: Case Report and Review of the Literature.

BACKGROUND: Leigh syndrome is an early-onset progressive neurodegenerative disorder typically involving lesions of the bilateral basal ganglia, thalami, and brainstem. Isolated involvement of the cerebellum is uncommon. PATIENT DESCRIPTION: We present a six-year-old boy with Leigh syndrome who presented with recurrent episodes of ataxia and dysarthria. He was diagnosed with Leigh syndrome at two years of age with bilateral basal ganglia lesions on brain magnetic resonance imaging (MRI). Genetic testing confirmed a diagnosis of Leigh syndrome secondary to a homoplasmic mitochondrial DNA mutation (m.9176T>C). He experienced regressive episodes (ages five and six years). Each regressive episode had a similar presentation with worsening of baseline ataxia and dysarthria. The first episode mimicked infectious cerebellitis, with elevated cerebral spinal fluid (CSF) protein and white blood cell count. No organisms were isolated from the CSF/blood during any of the regressive episodes. Brain MRI consistently showed cerebellar lesions, however cerebellar spectroscopy during the second episode found an elevated lactate peak, a decrease of the N-acetylaspartate peak, and elevation of the choline peak; consistent with an acute exacerbation of Leigh syndrome. CONCLUSIONS: Leigh syndrome can present primarily with involvement of the cerebellum, and it should be considered in the differential diagnosis for acute cerebellitis.

Smooth Muscle Hgs Deficiency Leads to Impaired Esophageal Motility.

As a master component of endosomal sorting complex required for transport proteins, hepatocyte growth factor-regulated tyrosine kinase substrate (Hgs) participates multiple cellular behaviors. However, the physiological role of Hgs in smooth muscle cells (SMCs) is by far unknown. Here we explored the in vivo function of Hgs in SMCs by using a conditional gene knockout strategy. Hgs deficiency in SMCs uniquely led to a progressive dilatation of esophagus with a remarkable thinning muscle layer. Of note, the mutant esophagus showed a decreased contractile responsiveness to potassium chloride and acetylcholine stimulation. Furthermore, an increase in the inhibitory neurites along with an intense infiltration of T lymphocytes in the mucosa and muscle layer were observed. Consistently, Hgs deficiency in SMCs resulted in a disturbed expression of a set of genes involved in neurotrophin and inflammation, suggesting that defective SMC might be a novel source for excessive production of cytokines and chemokines which may trigger the neuronal dysplasia and ultimately contribute to the compromised esophageal motility. The data suggest potential implications in the pathogenesis of related diseases such as gastroesophageal reflux disease.

Systemic sclerosis-rheumatoid arthritis overlap syndrome: a unique combination of features suggests a distinct genetic, serological and clinical entity.

OBJECTIVE: To determine the genetic, clinical and serological characteristics of systemic sclerosis (SSc)-rheumatoid arthritis (RA) overlap syndrome. METHODS: Clinical manifestations and immunolaboratory features of 22 SSc-RA patients were assessed. The HLA-DR genotype of the 22 SSc-RA patients determined by SSP-PCR was compared with that of 38 SSc patients, 100 RA patients and 50 healthy controls. RESULTS: All overlap patients fulfilled the American College of Rheumatology (ACR) criteria for SSc and RA. Five of the 22 patients (23%) had diffuse cutaneous SSc (dcSSc) and 17 patients (77%) had limited cutaneous SSc (lcSSc). Antinuclear antibody, anti-Scl70, IgM rheumatoid factor and anti-CCP antibody positivity were detected in 22 (100%), 5 (23%), 16 (73%) and 18 patients (82%), respectively. Seventeen patients (77%) had pulmonary fibrosis, 12 (55%) had oesophageal dismotility, 11 (50%) had cardiac and five (23%) had renal involvement. Hand joint destruction was observed in 18 patients (82%). Significantly increased frequencies of HLA-DR3 (36% vs 5%), HLA-DR7 (9% vs 4%), HLA-DR11 (36% vs 7%) and HLA-DRw53 (23% vs 5%) were observed in SSc-RA compared with RA patients (P < 0.05). Allele frequencies of the 'shared epitope' (HLA-DR1 and -DR4) were significantly increased in SSc-RA (32% and 27%, respectively) and RA patients (46% and 31%, respectively) in comparison with SSc patients (10.5% and 16%, respectively) or healthy controls (16% and 14%, respectively) (P < 0.05). CONCLUSIONS: To date this is the largest SSc-RA overlap cohort. Genetics, clinical and immunolaboratory features suggest a mixed phenotype. Our data suggest that SSc-RA overlap syndrome may be a distinct genetic, immunological and clinical entity.

Familial coexistence of achalasia and non-achalasic oesophageal dysmotility: evidence for a common pathogenesis.

In five of seven siblings of healthy parents, dysphagia developed during adolescence or early adult life. A barium swallow was normal in one patient but showed appearances considered to be consistent with achalasia in all others. Oesophageal manometry was successfully performed in four of the five patients, including the patient with symptoms but normal radiological appearance. One patient had achalasia, two had oesophageal body motor dysfunction associated with a hypertensive, but normally relaxing lower oesophageal sphincter, and one had diffuse oesophageal spasm alone. The occurrence of three different oesophageal dysmotility disorders within members of a single sibship suggests that these conditions are intimately related and probably genetically determined as an autosomal recessive trait.