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Background and ObjectivesFacioscapulohumeral muscular dystrophy type 2 (FSHD2) and arhinia are 2 distinct disorders caused by pathogenic variants in the same gene: SMCHD1. The mechanism underlying this phenotypic divergence remains unclear. In this study, we characterize the neuromuscular phenotype of individuals with arhinia caused by SMCHD1 variants and analyze their complex genetic and epigenetic criteria to assess their risk for FSHD2.MethodsEleven individuals with congenital nasal anomalies, including arhinia, nasal hypoplasia, or anosmia, underwent a neuromuscular examination, genetic testing, muscle ultrasound, and muscle MRI. Risk for FSHD2 was determined by combined genetic and epigenetic analysis of 4q35 haplotype, D4Z4 repeat length, and methylation profile. We also compared expression levels of pathogenic DUX4 mRNA in primary myoblasts or dermal fibroblasts (upon myogenic differentiation or epigenetic transdifferentiation, respectively) in these individuals vs those with confirmed FSHD2.ResultsAmong the 11 individuals with rare, pathogenic, heterozygous missense variants in exons 3–11 of SMCHD1, only a subset (n = 3/11; 1 male, 2 female; age 25–51 years) met the strict genetic and epigenetic criteria for FSHD2 (D4Z4 repeat unit length cis with a 4qA haplotype and D4Z4 methylation DUX4 expression in dermal fibroblasts under the epigenetic de-repression by drug treatment and in the primary myoblasts undergoing myogenic differentiation.DiscussionIn this cross-sectional study, we identified patients with arhinia who meet the full genetic and epigenetic criteria for FSHD2 and display the molecular hallmark of FSHD—DUX4 de-repression and expression in vitro—but who do not manifest with the typical clinicopathologic phenotype of FSHD2. The distinct dichotomy between FSHD2 and arhinia phenotypes despite an otherwise poised DUX4 locus implies the presence of novel disease-modifying factors that seem to operate as a switch, resulting in one phenotype and not the other. Identification and further understanding of these disease-modifying factors will provide valuable insight with therapeutic implications for both diseases.

BACKGROUND AND OBJECTIVES: Facioscapulohumeral muscular dystrophy type 2 (FSHD2) and arhinia are 2 distinct disorders caused by pathogenic variants in the same gene: SMCHD1. The mechanism underlying this phenotypic divergence remains unclear. In this study, we characterize the neuromuscular phenotype of individuals with arhinia caused by SMCHD1 variants and analyze their complex genetic and epigenetic criteria to assess their risk for FSHD2. METHODS: Eleven individuals with congenital nasal anomalies, including arhinia, nasal hypoplasia, or anosmia, underwent a neuromuscular examination, genetic testing, muscle ultrasound, and muscle MRI. Risk for FSHD2 was determined by combined genetic and epigenetic analysis of 4q35 haplotype, D4Z4 repeat length, and methylation profile. We also compared expression levels of pathogenic DUX4 mRNA in primary myoblasts or dermal fibroblasts (upon myogenic differentiation or epigenetic transdifferentiation, respectively) in these individuals vs those with confirmed FSHD2. RESULTS: Among the 11 individuals with rare, pathogenic, heterozygous missense variants in exons 3–11 of SMCHD1, only a subset (n = 3/11; 1 male, 2 female; age 25–51 years) met the strict genetic and epigenetic criteria for FSHD2 (D4Z4 repeat unit length

Objective:To summarize facioscapulohumeral muscular dystrophy (FSHD) diagnostic testing results from the University of Iowa Molecular Pathology Laboratory.Methods:All FSHD tests performed in the diagnostic laboratory January 2015-July 2019 were retrospectively reviewed. Testing was by restriction enzyme digestion and Southern blot analysis with sequencing of SMCHD1, if indicated. Cases were classified as FSHD1 (4q35 EcoRI size ≤40kb; 1-10 D4Z4 repeats), FSHD2 (permissive 4q35A allele, D4Z4 hypomethylation, and pathogenic SMCHD1 variant), or non-FSHD1,2. We also noted cases with borderline EcoRI fragment size (41-43kb; 11 D4Z4 repeats), cases that meet criteria for both FSHD1 and FSHD2, somatic mosaicism, and cases with hybrid alleles that add complexity to test interpretation.Results:Of the 1594 FSHD tests included in the analysis, 703 (44.1%) were diagnosed with FSHD. Among these positive tests, 664 (94.5%) met criteria for FSHD1 and 39 (5.5%) met criteria for FSHD2. Of all 1594 cases, 20 (1.3%) had a 4q35 allele of borderline size, 23 (1.5%) were somatic mosaics, and 328 (20.9%) had undergone translocation events. Considering only cases with at least one 4q35A allele, D4Z4 repeat number differed significantly among groups: FSHD1 cases median of 6.0 (IQR: 4-7) repeats, FSHD2 cases 15.0 (IQR: 12-22) repeats, and non-FSHD1,2 cases 28.0 (IQR: 19-40) repeats.Conclusion:FSHD1 accounts for 94.5% of genetically confirmed cases of FSHD. The data show a continuum of D4Z4 repeat numbers with FSHD1 samples having the fewest, FSHD2 an intermediate number, and non-FSHD1,2 the most.

A 30-year-old man who recently immigrated from Liberia was admitted to the neurology service for diffuse weakness. He reported 7 years of painless progressive weakness and atrophy. He noted that his legs began to get weak first, which manifested as difficulty keeping up with his peers while playing soccer. This progressively worsened until he had great difficulty walking and arising from a seated position. A few years after the onset of leg weakness, he developed arm weakness. He denied sensory loss. He had some back pain but no limb pain. He denied fasciculations, cramping, or constitutional symptoms. He was not on medications and denied any toxic exposures. His parents were physically normal but were first cousins. He had 2 children, ages 2 and 4 years, who were physically normal. The authors acknowledge Terese Nelson for performing the muscle biopsy immunostaining and Mary Cox for performing the Western blotting.

ObjectiveTo determine whether congenital arhinia/Bosma arhinia microphthalmia syndrome (BAMS) and facioscapulohumeral muscular dystrophy type 2 (FSHD2), 2 seemingly unrelated disorders both caused by heterozygous pathogenic missense variants in the SMCHD1 gene, might represent different ends of a broad single phenotypic spectrum associated with SMCHD1 dysfunction.MethodsWe examined and/or interviewed 14 patients with FSHD2 and 4 unaffected family members with N-terminal SMCHD1 pathogenic missense variants to identify BAMS subphenotypes.ResultsNone of the patients with FSHD2 or family members demonstrated any congenital defects or dysmorphic features commonly found in patients with BAMS. One patient became anosmic after nasal surgery and one patient was hyposmic; one man was infertile (unknown cause) but reported normal pubertal development.ConclusionThese data suggest that arhinia/BAMS and FSHD2 do not represent one phenotypic spectrum and that SMCHD1 pathogenic variants by themselves are insufficient to cause either of the 2 disorders. More likely, both arhinia/BAMS and FSHD2 are caused by complex oligogenic or multifactorial mechanisms that only partially overlap at the level of SMCHD1.

To determine the frequency of urologic and gastrointestinal (GI) symptoms in a cohort of individuals with dystroglycanopathy compared with healthy household controls.Participants in a North American dystroglycanopathy natural history study (NCT00313677) and other members of their households completed a questionnaire modified from validated instruments and clinical criteria. Urologic and GI symptom frequency, effect on patient life, and medications taken for these symptoms were assessed. Those younger than 4 years or not toilet trained were excluded. Healthy human bladder, esophagus, and duodenum from surgical specimens were immunostained for glycosylated α-dystroglycan.Thirty of 58 potential participants with dystroglycanopathy (51.7%) and 16 household controls participated. Subjects were aged 6 to 51 years (mean 26.7); 60.0% were female. Controls were aged 7 to 55 years (mean 34.6); 56.3% were female. The dystroglycanopathy cohort had higher frequency of urinary voiding symptoms (p = 0.02), higher urologic symptom scores (p = 0.05), and higher dysphagia symptom scores (p = 0.04). A correlation existed between urologic symptom score and effect on life (r = 0.71; 95% confidence interval 0.46, 0.85; p0.0001) and between dysphagia symptom score and effect on life (r = 0.72; 95% confidence interval 0.48, 0.86; p0.0001). Glycosylated α-dystroglycan was present in visceral smooth muscle of all normal tissues analyzed.Urologic symptoms and dysphagia are reported more frequently by individuals with dystroglycanopathies than by household controls. These symptoms can cause a perceived negative effect on patient life. Our results suggest urologic and GI dysfunction may be part of the dystroglycanopathy phenotype, and that questions about these symptoms should be incorporated into routine care because they may influence medical management.

Dystroglycanopathies are characterized by deficient O-mannosyl glycosylation of α-dystroglycan (αDG) and represent an expanding genetically, biochemically, and clinically heterogeneous group of muscular dystrophies. Currently, there are 18 known genes leading to forms of α-dystroglycan–related dystrophy (αDG-RD), ranging in severity from a Walker-Warburg phenotype with severe brain malformations and hypotonia to milder childhood- or adult-onset limb-girdle muscular dystrophy (LGMD) phenotypes with or without intellectual disability.1,2

Objective: To investigate the effects of NEFL Glu396Lys mutation on the expression and assembly of neurofilaments (NFs) in cutaneous nerve fibers of patients with Charcot-Marie-Tooth disease type 2E (CMT2E). Methods: A large family with CMT2E underwent clinical, electrophysiologic, and skin biopsy studies. Biopsies were processed by indirect immunofluorescence (IF), electron microscopy (EM), and Western blot analysis. Results: The clinical features demonstrated intrafamilial phenotypic variability, and the electrophysiologic findings revealed nerve conductions that were either slow or in the intermediate range. All patients had reduced or absent compound muscular action potential amplitudes. Skin biopsies showed axons labeled with the axonal markers protein gene product 9.5 and α-tubulin, but not with NFs. The results of Western blot analysis were consistent with those of IF, showing reduced or absent NFs and normal expression of α-tubulin. EM revealed clusters of regenerated fibers, in absence of myelin sheath abnormalities. Both IF and EM failed to show NF aggregates in dermal axons. The morphometric analysis showed a smaller axonal caliber in patients than in controls. The study of the nodal/paranodal architecture demonstrated that sodium channels and Caspr were correctly localized in patients with CMT2E. Conclusions: Decrease in NF abundance may be a pathologic marker of CMT2E. The lack of NF aggregates, consistent with prior studies, suggests that they occur proximally leading to subsequent alterations in the axonal cytoskeleton. The small axonal caliber, along with the normal molecular architecture of nodes and paranodes, explain the reduced velocities detected in patients with CMT2E. Our results also demonstrate that skin biopsy can provide evidence of pathologic and pathogenic abnormalities in patients with CMT2E.

Fukutin-related protein ( FKRP; OMIM #606596) is critical for the appropriate glycosylation of α-dystroglycan, a component of the dystrophin-glycoprotein complex. The 12-kb FKRP gene is composed of 3 noncoding exons and 1 exon encompassing the entire open reading frame.1 Mutations in FKRP cause autosomal recessive muscular dystrophy with a wide range of clinical severity. A common missense mutation, c.826C>A (p.L276I), has been identified. Generally, individuals homozygous for this mutation have a mild form of limb-girdle muscular dystrophy (LGMD) 2I, compound heterozygotes with 1 c.826C>A allele have a more severe form of LGMD 2I, and those with 2 unique alleles are most severely affected, including some with congenital muscular dystrophy.1,2 We report a high incidence of myoglobinuria and muscle pain in a retrospective study of patients with LGMD 2I. ### Methods. #### Standard protocol approvals, registrations, and patient consents. Institutional Review Board approval was obtained for all recruitment and data collection. Written informed consent was obtained from all participants or their legal guardians. This study was posted on clinicaltrials.gov (NCT00313677). All patients with FKRP mutations were eligible for enrollment from 2006 to the present. #### Genetic testing. FKRP mutations were confirmed in the University of Iowa …

Objective: To evaluate the incidence of the facioscapulohumeral dystrophy (FSHD) 4q35 deletion in patients with facial-sparing scapular myopathy.Background: Scapular winging is typical of FSHD but may also be prominent in other muscle disorders including scapuloperoneal syndromes. With DNA testing, it is possible to determine if patients with facial-sparing scapular myopathy have FSHD.Methods: Fourteen of 17 unrelated patients with facial-sparing scapular myopathy, seen over a 7-year period at a regional neuromuscular center, agreed to have DNA testing for FSHD. The clinical and laboratory features of these patients were also noted.Results: Of the 14 patients, 10 (71%) had restriction fragments consistent with the 4q35 deletion. The mean size of the smaller fragment following EcoRI digestion was 29.5 kb (range 20 to 39). The mean age at onset was 19.9 years; at presentation, 44.7 years. Except for the absence of facial weakness, most patients had clinical and laboratory features otherwise consistent with FSHD. Five patients (50%) had a positive family history of similar weakness. Following removal of outliers, the Pearson correlation coefficient (r) value between EcoRI fragment size and age at onset was 0.64, and between fragment size and limb muscle strength, 0.64.Conclusion: The FSHD 4q35 deletion was found in 71% of the facial-sparing scapular myopathy patients. They otherwise resemble typical FSHD patients in age at onset, physical characteristics, and association between fragment size and disease severity.

We studied two siblings with chorea and amyotrophy of adult onset and spherocytic hemolytic anemia. Autopsy revealed an atrophic striatum with iron deposition and spheroid bodies. Degeneration of the substantia nigra and spinal cord anterior horns was seen without iron deposition. The disorder seems to be a variant of the chorea-amyotrophy-acanthocytosis syndrome, and the pathology may account for evidence of parkinsonism and amyotrophy in that syndrome. Acanthocytosis may not be the only hematologic abnormality in this disorder.