Antineutrophil cytoplasmic antibody-associated vasculitis with predominant truncal muscle weakness: a retrospective case series

Introduction

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) frequently leads to mononeuritis multiplex, which are characterized by distal weakness associated with sensory disturbances. Although AAV has also been reported to be associated with myopathy, the pathogenesis and characteristics remain unclear. We aimed to show the clinical and laboratory findings in AAV-associated myopathy.

Methods

This retrospective single-center study included patients with the diagnosis of AAV who had been admitted to the neurology department and had biopsy specimens of muscle and/or nerve tissue.

Results

We identified four patients with a distinct clinical presentation of muscle weakness in the trunk and proximal limbs. The weakness resembled that of inflammatory muscle disease. These patients denied symptoms associated with neuropathy, and had normal serum creatine kinase (CK) levels. Needle electromyography (needle EMG) showed spontaneous electrical activity at rest, and results of magnetic resonance imaging (MRI) suggested inflammatory myopathy. Muscle biopsy specimens from all four patients revealed vasculitis and inflammation in proximity to the affected vessels, without any discernible characteristics of other myopathies. The patients also complained of symptoms affecting other organs, such as the ears and kidneys, which is typical of AAV cases. Remission induction therapy, such as cyclophosphamide pulse therapy in addition to oral prednisolone, were effective for all four patients. However, relapses occurred in two patients during maintenance therapy and two patients died of aspiration pneumonia.

Discussion

The clinical course of our patients might represent a subtype of AAV that is characterized by muscle weakness of the trunk and proximal extremities and arises from vasculitis within the muscles. The clinical manifestations of our patients were similar to those of patients with inflammatory myopathy with regard to the distribution of muscle weakness, MRI and needle EMG findings. However, there are notable differences between AAV associated myopathy vs. inflammatory myositis like dermatomyositis; (1) the absence of elevated CK levels, (2) the presence of complications in other organs, (3) distinct pathological findings, and (4) severe outcomes. Awareness that AAV patients with muscle involvement could have a subtype of AAV that seriously affects various organs is critical for an accurate diagnosis and effective therapeutic management.

Iliopsoas Muscle Weakness as a Key Diagnostic Marker in HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP)

Human T-cell leukemia virus-1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a slowly progressive neurological disease that arises from HTLV-1 infection. Pathologically, the condition is characterized by diffuse myelitis, which is most evident in the thoracic spinal cord. Clinical manifestations of the infectious disease, HAM/TSP, are empirically known to include weakness of the proximal muscles of the lower extremities and atrophy of the paraspinal muscles, which is characteristic of the distribution of disturbed muscles usually seen in muscular diseases, except that the upper extremities are almost normal. This unique clinical presentation is useful information for physicians and physical therapists involved in diagnosing and rehabilitating patients with HAM/TSP, as well as critical information for understanding the pathogenesis of HAM/TSP. However, the precise pattern of muscle involvement in this condition has yet to be reported. The purpose of this study was to identify the muscles affected by HAM/TSP in order to understand the pathogenesis of HAM/TSP as well as to aid in the diagnosis and rehabilitation of HAM/TSP. A retrospective review of medical records was conducted on 101 consecutively admitted patients with HAM/TSP at Kagoshima University Hospital. Among 101 patients with HAM/TSP, all but three had muscle weakness in the lower extremities. Specifically, the hamstrings and iliopsoas muscle were the most frequently affected in over 90% of the patients. Manual muscle testing (MMT) revealed that the iliopsoas was the weakest of the muscles assessed, a consistent feature from the early to advanced stages of the disease. Our findings demonstrate a unique distribution of muscle weakness in HAM/TSP, with the proximal muscles of the lower extremities, particularly the iliopsoas muscle, being the most frequently and severely affected.

Further evidence of muscle involvement in neurodevelopmental disorder with epilepsy, spasticity, and brain atrophy

TRAPPC4-related neurodevelopmental disorder with epilepsy, spasticity, and brain atrophy (MIM# 618741) is a recently described TRAPPopathy with clinical findings of developmental delay, seizures, postnatal microcephaly, spasticity, facial dysmorphism, and cerebral and cerebellar atrophy. Muscle involvement, a frequent finding in TRAPPopathies, was observed in one individual with TRAPPC4-related disorder previously. Only a single variant, an in-frame deletion in one family has been reported outside a recurrent disease-causing variant. We report three individuals from two Indian families harboring novel bi-allelic missense variants c.191T>C and c.278C>T (NM_016146.6) in TRAPPC4 with classic clinical presentation in one and milder and later onset in the other family. We provide further evidence for muscle involvement and review the detailed phenotypic findings in individuals reported with this disorder till date.

Anti-nuclear matrix protein 2 antibody-positive inflammatory myopathies represent extensive myositis without dermatomyositis-specific rash

OBJECTIVES

Myositis-specific autoantibodies (MSAs) define distinct clinical subsets of idiopathic inflammatory myopathies (IIMs). The anti-nuclear matrix protein 2 (NXP2) antibody, a MSA detected in juvenile/adult IIMs, has been reported to be associated with a high risk of subcutaneous calcinosis, subcutaneous oedema, and internal malignancies. The study aimed to clarify the clinical features of anti-NXP2 antibody-positive IIMs in detail.

METHODS

This multi-centre retrospective observational study on 76 anti-NXP2 antibody-positive patients. The antibody was detected via a serological assay using immunoprecipitation and western blotting. The patients were selected from 162 consecutive Japanese patients with IIMs.

RESULTS

The cohort of anti-NXP2 antibody-positive IIMs included 29 juvenile patients and 47 adult patients. Twenty-seven (35.5%) patients presented with polymyositis phenotype without dermatomyositis-specific skin manifestations (heliotrope rash or Gottron sign/papules); this was more common in the adults than children (48.9% vs. 15.8%, P < 0.01). Nine (11.8%) patients had subcutaneous calcinosis, and 20 (26.3%) patients had subcutaneous oedema. In addition, the proportion of patients with muscle weakness extending to the distal limbs was high (36 patients [47.4%]) in this cohort. Adult patients had a higher prevalence of malignancy than the general population (age-standardised incidence ratio of malignancies: 22.4).

CONCLUSION

Anti-NXP2 antibody-positive IIMs, which include dermatomyositis sine dermatitis, are characterised by atypical skin manifestations and extensive muscular involvement.

Rhabdomyolysis in a Patient with Polyarteritis Nodosa

Polyarteritis nodosa (PAN) is a medium vessel vasculitis affecting systemic organs. Muscle involvement of PAN usually lacks elevation of creatinine kinase (CK). We herein report a case of PAN with rhabdomyolysis. A 71-year-old man was hospitalized because of muscle weakness of the lower limbs that persisted for 1 month. On a physical examination, rapidly progressive lower proximal muscle weakness and bilateral drop foot were observed. His blood test showed an elevation in the C-reactive protein (19.5 mg/dL) and CK (13,435 IU/L) levels and negativity for anti-neutrophilic cytoplasmic antibody. Computed tomographic angiography showed stenosis of the left renal artery. Electromyogram indicated mono-neuritis multiplex pattern, and enhanced magnetic resonance imaging demonstrated discretely granular hyperintensities on T2 and slow tau inversion recovery in his femoral muscles. A femoral muscle-biopsy specimen showed fibrinoid necrosis of medium-sized vessels and disruption of the elastic lamina of the vessel wall in fascia. Furthermore, muscle necrosis was localized depending on the arterial distribution, suggesting ischemic changes in the muscles. Given these findings, he was diagnosed with PAN with rhabdomyolysis and treated with methyl-prednisolone pulse therapy followed by oral prednisolone at 50 mg/day. He was additionally treated with monthly intravenous cyclophosphamide at 500 mg. Sustained remission has been obtained for two months since the treatment. Although rhabdomyolysis rarely manifests with PAN, it should be included in a differential diagnosis of febrile patients presenting with acute myalgia and weakness with CK elevation.

A novel PGK1 mutation associated with neurological dysfunction and the absence of episodes of hemolytic anemia or myoglobinuria

Phosphoglycerate kinase (PGK) deficiency affects three different organs: red blood cells (RBC), the central nervous system, and muscles. Next-generation sequencing identified a hemizygous PGK1 mutation (p.V217I) in a 16-year-old Japanese male patient presenting with intellectual disability and episodes of muscle weakness of unknown etiology. Enzymatic analysis demonstrated slightly lower RBC-PGK activity and compensatory increases of other glycolysis enzymes. This is the first PGK1 mutation found through next-generation sequencing.

Clinical and Pathological Features of Korean Patients with DNM2-Related Centronuclear Myopathy

Background and Purpose

Centronuclear myopathy (CNM) is characterized by the presence of central nuclei within a large number of muscle fibers. Mutations of the dynamin 2 gene (DNM2) are common causes of autosomal dominant or sporadic CNM. The aim of this study was to characterize the clinical and pathological features of CNM relative to the presence of DNM2 mutations.

Methods

Six patients with clinical and pathological features of CNM were recruited. Detailed clinical and pathological findings were analyzed according to the presence of DNM2 mutations.

Results

We detected DNM2 mutations in four of the six sporadic CNM patients, and identified the following distinct clinical and pathological features in those patients with DNM2 mutations: preferential involvement of the distal lower limbs, typical nuclear centralization, and radially distributed sarcoplasmic strands in muscle pathology. In contrast, those without DNM2 mutations exhibited rather diffuse muscular involvement, and nuclear internalization and myofibrillar disorganization were more pronounced features of their muscle pathology.

Conclusions

These findings suggest the presence of specific features in Korean CNM patients. A detailed clinical and pathological examination of CNM patients would be helpful for molecular genetic analyses of this condition.