Late-onset rod myopathy associated with monoclonal gammopathy

Sporadic Late-Onset Nemaline Myopathy: Current Landscape

PURPOSE OF REVIEW

Sporadic late-onset nemaline myopathy (SLONM) is a rare adult-onset, acquired, muscle disease that can be associated with monoclonal gammopathy or HIV infection. The pathological hallmark of SLONM is the accumulation of nemaline rods in muscle fibers. We review here current knowledge about its presentation, pathophysiology, and management.

RECENT FINDINGS

SLONM usually manifests with subacutely progressive proximal and axial weakness, but it can also present with chronic progressive weakness mimicking muscular dystrophy. The pathophysiology of the disease remains poorly understood, with evidence pointing to both autoimmune mechanisms and hematological neoplasia. Recent studies have identified histological, proteomic, and transcriptomic alterations that shed light on disease mechanisms and distinguish SLONM from inherited nemaline myopathies. A majority of SLONM patients respond to intravenous immunoglobulins, chemotherapy, or hematopoietic stem cell transplant. SLONM is a treatable myopathy, although its underlying etiology and pathomechanisms remain unclear. A high degree of suspicion should be maintained for this disease to reduce diagnostic delay and treatment in SLONM and facilitate its distinction from inherited nemaline myopathies.

Molecular signatures of inherited and acquired sporadic late onset nemaline myopathies

Acquired sporadic late onset nemaline myopathy (SLONM) and inherited nemaline myopathy (iNM) both feature accumulation of nemaline rods in muscle fibers. Unlike iNM, SLONM is amenable to therapy. The distinction between these disorders is therefore crucial when the diagnosis remains ambiguous after initial investigations. We sought to identify biomarkers facilitating this distinction and to investigate the pathophysiology of nemaline rod formation in these different disorders. Twenty-two muscle samples from patients affected by SLONM or iNM underwent quantitative histological analysis, laser capture microdissection for proteomic analysis of nemaline rod areas and rod-free areas, and transcriptomic analysis. In all iNM samples, nemaline rods were found in subsarcolemmal or central aggregates, whereas they were diffusely distributed within muscle fibers in most SLONM samples. In SLONM, muscle fibers harboring nemaline rods were smaller than those without rods. Necrotic fibers, increased endomysial connective tissue, and atrophic fibers filled with nemaline rods were more common in SLONM. Proteomic analysis detected differentially expressed proteins between nemaline rod areas and rod-free areas, as well as between SLONM and iNM. These differentially expressed proteins implicated immune, structural, metabolic, and cellular processes in disease pathophysiology. Notably, immunoglobulin overexpression with accumulation in nemaline rod areas was detected in SLONM. Transcriptomic analysis corroborated proteomic findings and further revealed substantial gene expression differences between SLONM and iNM. Overall, we identified unique pathological and molecular signatures associated with SLONM and iNM, suggesting distinct underlying pathophysiological mechanisms. These findings represent a step towards enhanced diagnostic tools and towards development of treatments for SLONM.

Clinicopathologic Profiles of Sporadic Late-Onset Nemaline Myopathy: Practical Importance of Anti-α-Actinin Immunostaining

BACKGROUND AND OBJECTIVES

Sporadic late-onset nemaline myopathy (SLONM) is a treatable or otherwise fatal myopathy. Diagnosis of SLONM is still challenging, and no therapeutic consensus has been achieved. Here, we reported the clinicopathologic features and long-term follow-up data of SLONM in a Chinese cohort.

METHODS

We performed a retrospective evaluation of clinical, pathologic, and treatment outcomes of 17 patients with SLONM diagnosed between March 1986 and April 2021 at our neuromuscular center. Immunohistochemistry (IHC) with antibodies against 5 Z-disc-associated proteins was performed in the muscle biopsies of SLONM to identify a potential pathologic marker in aid of diagnosis. In comparison, we also performed muscle IHC in patients with selective type II fiber atrophy (n = 22), neurogenic atrophy (n = 22), mitochondrial myopathy (n = 5), immune-mediated necrotizing myopathy (n = 5), and normal controls (n = 5).

RESULTS

Most of the patients exhibited asymmetric limb muscles weakness (71%, 12/17) and neck extensor weakness (53%, 9/17). Immunofixation electrophoresis was performed in 11 patients, and 4 of them were identified with monoclonal gammopathy of undetermined significance (MGUS). EMG from 16 patients demonstrated a myopathic pattern with spontaneous activities in 69% (11/16) of them. Muscle MRI showed preferential involvement of paraspinal, gluteus minimus and medius, semimembranosus, and soleus muscles. Suspected nemaline bodies on modified Gomori trichrome were confirmed by IHC using anti-α-actinin antibody (100%, 17/17), anti-myotilin antibody (94%, 16/17), anti-desmin antibody (94%, 16/17), anti-α-B crystallin antibody (65%, 11/17), and anti-telethonin antibody (18%, 3/17) with various positive rates. Notably, anti-α-actinin IHC showed the highest percentage of strongly positive staining (77%, 13/17), being the only one without negative results. Moderate improvement following autologous stem cell transplantation (ASCT) was noted in 3/4 patients with MGUS; favorable outcomes were also achieved in 6/7 patients without MGUS, including 3 patients with complete recovery who were given a combined treatment of prednisone and another immunosuppressant.

DISCUSSION

SLONM is a treatable myopathy with ASCT or traditional immunotherapy, especially when combined with steroids and immunosuppressants. Anti-α-actinin immunostaining is the most reliable pathologic marker to identify rod-bearing fibers, and it should be performed routinely in adult patients with undiagnosed nonnecrotic myopathies.

A case of sporadic late-onset nemaline myopathy with monoclonal gammopathy of undetermined significance: long-term observation of neurological symptoms after autologous stem-cell transplantation

A 47-year-old woman presented with progressive limb weakness. A neurological examination revealed proximal dominant symmetrical muscle weakness in her limbs, and electromyography revealed complex repetitive discharges and short motor unit potentials with positive sharp waves in the biceps. We observed early recruitment in the quadriceps, and laboratory tests revealed normal creatine kinase. Serum protein electrophoresis showed monoclonal IgG-lambda, but the bone marrow aspiration specimen was normal. A muscle biopsy revealed nemaline rod accumulations in the muscle fibers; based on the results, we diagnosed the patient with sporadic late-onset nemaline myopathy with monoclonal gammopathy of undetermined significance (SLONM-MGUS). We administered repeated intravenous immunoglobulin, but her limb weakness continued, and she developed a restrictive ventilatory defect. The patient received melphalan, followed by autologous stem-cell transplantation (ASCT). Her upper extremity strength and respiratory capability improved within one year after ASCT; however, it was not until six years after ASCT that her atrophied lower extremities strengthened. A discrepancy in the timeline of treatment response between the upper or respiratory muscles and the atrophied lower limb was characteristic in the patient, suggesting that the efficacy of ASCT on SLONM-MGUS should be evaluated in the long term, especially in severely atrophied muscles. In addition, this case showed that ASCT for SLOMN-MGUS is an effective treatment option in Asian populations.

Impact of hematologic complete response in the treatment of sporadic late-onset nemaline myopathy associated with monoclonal gammopathy

Monoclonal gammopathy of undetermined significance (MGUS) may be associated with pathologies with severe neuromuscular manifestations such as sporadic late-onset nemaline myopathy (SLONM). We describe a difficult to diagnose case of SLNOM with marked clinical improvement after achieving gammopathy complete hematologic response.

Chemotherapy-based approach is the preferred treatment for sporadic late-onset nemaline myopathy with a monoclonal protein

Sporadic late-onset nemaline myopathy (SLONM) associated with monoclonal protein (MP) is a rare disease with an aggressive, and often fatal course. Whether SLONM + MP represents a malignancy or dysimmune disease remains unclear. Currently, two main approaches are used to treat SLONM + MP: nonchemotherapy-based treatment (immunosuppression, intravenous immunoglobulins, plasmapheresis and plasma exchange) or chemotherapy with or without autologous stem cell transplantation. Due to the rare occurrence of the disease, the best treatment modality is unknown. We analyzed treatment and outcomes in a large cohort of 53 patients with SLONM + MP: four our own patients and 49 cases from published literature. Neurological improvement in the nonchemotherapy group (N = 25) was observed in 52% of patients: 8% reached marked improvement, 8% moderate response, 36% mild response; none reached complete remission (CR). In the chemotherapy group (N = 28), neurological improvement was seen in 86% of patients: 46% reached CR, 25% marked response, 11% moderate response and 4% mild response. The best neurological improvement correlated with deep hematological remission. Mean time to best response in the chemotherapy group was 8 months versus 21 months in the nonchemotherapy group (P < .001). Overall survival was higher in patients in the chemotherapy group. A chemotherapy approach should be the preferred treatment for patients with SLOMN + MP with the goal to reach complete hematologic remission. Based on the clinical, morphological peculiarities, aggressive disease course and superior clinical benefits of chemotherapy over nonchemotherapy, SLONM + MP should be considered as a hematological malignancy with the presence of MP of clinical rather than undetermined significance.

Inflammatory features in sporadic late-onset nemaline myopathy are independent from monoclonal gammopathy

Sporadic late-onset nemaline myopathy (SLONM) is a rare adult-onset non-hereditary disease with subacute proximal muscle and often axial muscle weakness, characterized by the presence of nemaline bodies in skeletal muscle biopsies. Considering its association with concurrent monoclonal gammopathy of undetermined significance (MGUS), the disease is classified into two major subtypes (1) SLONM without MGUS (SLONM-noMGUS) and (2) with MGUS (SLONM-MGUS) association. SLONM associated with HIV infection (SLONM-HIV) is also reported. SLONM-MGUS has been shown to be associated with poorer prognosis and required aggressive treatment including high-dose melphalan and autologous stem cell transplantation. The approach is currently debatable as recent reports suggested effectiveness of intravenous immunoglobulin as initial treatment with indifference of overall survival despite the presence of MGUS. Our study aimed to find an underlying basis by review of pathological features in 49 muscle biopsy proven-SLONM from two large tertiary centers in Japan and Germany (n = 49: SLONM-noMGUS = 34, SLONM-MGUS = 13, SLONM-HIV = 2). We compared pathological findings in SLONM-noMGUS and SLONM-MGUS and focused on the presence of any detectable inflammatory features by immunohistochemistry. The clinical and histological features in SLONM-noMGUS and SLONM-MGUS were not distinctively different except for more common regenerating fibers (>5% of myofibers) present in SLONM-MGUS (p < 0.01). HLA-ABC expression and fine granular p62 were observed in 66.7% and 78.3% of SLONM, respectively. The predominant inflammatory cells were CD68⁺ cells. The inflammatory cells showed positive correlations with the percentage of nemaline-containing fibers (p < 0.001). In conclusion, inflammatory features are present although rather mild in SLONM. This finding contributes to the hypothesis of an acquired inflammatory disease pathogenesis and opens the possibility to offer immunotherapy in SLONM with inflammatory features regardless of the monoclonal gammopathy status.

Sporadic late onset nemaline myopathy with monoclonal gammopathy of undetermined significance: two cases with long term stability

Monoclonal gammopathy of undetermined significance (MGUS) associated to sporadic late onset nemaline myopathy (SLONM) is a rare and severely disabling condition of quickly progressive limb girdle acquired myopathy. It is believed by some authors to be due to myotoxicity of light chain deposits. Two female patients were diagnosed with MGUS associated SLONM. In the first case, diagnosis was delayed by 6 years thus giving time for a severe generalized myopathy and cardiomyopathy to develop. A single anti-myeloma chemotherapy with lenalidomide markedly improved and stabilized the patient’s condition despite respiratory and cardiac insufficiency. In our second patient the condition was identified one year after onset of the first symptom and markedly improved after autologous bone marrow transplantation and lenalidomide. Clinicians should be aware of monoclonal gammopathy associated sporadic late onset nemaline myopathy as this acquired muscle disorder, although extremely rare, may be reversed by adequate management.

Sporadic late-onset nemaline myopathy with monoclonal gammopathy of undetermined significance

PURPOSE OF REVIEW

Sporadic late-onset nemaline myopathy (SLONM) with monoclonal gammopathy of undetermined significance (MGUS) is a rare subacute progressive muscle disease. The prognosis is poor due to severe respiratory insufficiency. Recently, however, autologous stem-cell transplantation following high-dose melphalan has been shown to be effective unless there is delay before the treatment. Therefore, early recognition of the disease is important. This review gives an overview of recent advances in SLONM-MGUS, which could help to understand clinical and pathological features and treatment.

RECENT FINDINGS

Efficacy of autologous stem-cell transplantation following high-dose melphalan has been demonstrated in a long-term observation study. Subsequently, reports from other groups also have supported it. Furthermore, efficacy of chemotherapy toward plasma cell dyscrasia without stem-cell transplantation have been reported as well. A few case reports have suggested the presence of cardiac involvement related to SLONM-MGUS.

SUMMARY

SLONM-MGUS is now considered as a treatable disease. Antiplasma cell dyscrasia therapy is a promising therapeutic option. Meanwhile, the pathomechanic link between muscle degeneration and monoclonal gammopathy remains unclear and further investigations are warranted.

Monoclonal gammopathy with both nemaline myopathy and amyloid myopathy

Monoclonal gammopathies due to plasma cell dyscrasias can induce diverse rare neuromuscular disorders. Deposition of monoclonal antibody light chains in skeletal muscle causes amyloid myopathy. Monoclonal gammopathy is occasionally associated with sporadic late-onset nemaline myopathy. Here we report a monoclonal gammopathy patient with both sporadic late-onset nemaline myopathy and amyloid myopathy. The diagnoses were based on immunofixation electrophoresis of urine, and serum for free light chain assay, Congo red staining and Thioflavin S staining of muscle biopsies, as well as immunohistochemical staining and electron-microscopic observation. Nemaline myopathy and amyloid myopathy can present in the same patient with monoclonal gammopathy.

Sporadic late-onset nemaline myopathy: clinico-pathological characteristics and review of 76 cases

BACKGROUND

Sporadic late-onset nemaline myopathy (SLONM) is a rare, late-onset muscle disorder, characterized by the presence of nemaline rods in muscle fibers. Phenotypic characterization in a large cohort and a comprehensive overview of SLONM are lacking.

METHODS

We studied the clinico-pathological features, treatment and outcome in a large cohort of 76 patients with SLONM, comprising 10 new patients and 66 cases derived from a literature meta-analysis (PubMed, 1966-2016), and compared these with 15 reported HIV-associated nemaline myopathy (HIV-NM) cases. In 6 SLONM patients, we performed a targeted next-generation sequencing (NGS) panel comprising 283 myopathy genes.

RESULTS

SLONM patients had a mean age at onset of 52 years. The predominant phenotype consisted of weakness and atrophy of proximal upper limbs in 84%, of proximal lower limbs in 80% and both in 67%. Other common symptoms included axial weakness in 68%, as well as dyspnea in 55% and dysphagia in 47% of the patients. In 53% a monoclonal gammopathy of unknown significance (MGUS) was detected in serum. The mean percentage of muscle fibers containing rods was 28% (range 1-63%). In 2 cases ultrastructural analysis was necessary to detect the rods. The most successful treatment in SLONM patients (all with MGUS) was autologous peripheral blood stem cell therapy. A targeted NGS gene panel in 6 SLONM patients (without MGUS) did not reveal causative pathogenic variants. In a comparison of SLONM patients with and without MGUS, the former comprised significantly more males, had more rapid disease progression, and more vacuolar changes in muscle fibers. Interestingly, the muscle biopsy of 2 SLONM patients with MGUS revealed intranuclear rods, whereas this feature was not seen in any of the biopsies from patients without paraproteinemia. Compared to the overall SLONM cohort, significantly more HIV-NM patients were male, with a lower age at onset (mean 34 years). In addition, immunosuppression was more frequently applied with more favorable outcome, and muscle biopsies revealed a significantly higher degree of inflammation and necrosis in this cohort. Similar to SLONM, MGUS was present in half of the HIV-NM patients.

CONCLUSIONS

SLONM presents a challenging, but important differential diagnosis to other neuromuscular diseases of adult onset. Investigations for MGUS and HIV should be performed, as they require distinct but often effective therapeutic approaches. Even though SLONM and HIV-NM show some differences, there exists a large clinico-pathological overlap between the 2 entities.

Two cases of sporadic late onset nemaline myopathy effectively treated with immunotherapy

Sporadic late onset nemaline myopathy (SLONM) associated with monoclonal gammopathy of undetermined significance (MGUS) is an adult onset myopathy with poor clinical outcomes, requiring high-dose intravenous melphalan with autologous peripheral blood stem cell transplantation (HDM-SCT). Here we report two cases of SLONM associated with MGUS in which improvements were achieved only with immunotherapy. A 39-year-old woman had a two-year history of dropped head syndrome and progressive proximal weakness. On admission, she was able to walk with assistance and had lordosis with camptocormia. Combination therapy with plasmapheresis and intravenous immunoglobulin in addition to intravenous methylprednisolone pulse therapy ameliorated camptocormia and proximal weakness after one year. A 51-year-old man had difficulty in raising his arms and required walking assistance prior to visiting our hospital. He had proximal weakness and atrophy, winged scapulae, and gait disturbance. After combination immunotherapy, no progression was observed for 13 years. In both cases, patients did not desire to undergo HDM-SCT, and IgG kappa monoclonal protein was positive, of which the levels were normalized after immunotherapy. Combination immunotherapy can be a possible alternative to HDM-SCT in patients with SLONM. Both patients showed myogenic changes with abundant fibrillation, and needle EMG revealed positive sharp waves. Case 1 showed high signal intensities in MRI STIR/T2WI in muscles showing weakness. These findings are commonly observed in patients with myositis, suggesting that, without muscle biopsy, SLONM may be misdiagnosed as myositis. Muscle biopsy revealed scattered fibers with nemaline bodies without type 2B deficiency, which are important pathological findings that differentiate SLONM from congenital nemaline myopathy.

Nemaline myopathy and heart failure: role of ivabradine; a case report

Background

Nemaline myopathy (NM) is a rare congenital myopathy characterized by muscle weakness, hypotonia and the presence in muscle fibers of inclusions known as nemaline bodies and a wide spectrum of clinical phenotypes, ranging from severe forms with neonatal onset to asymptomatic forms. The adult-onset form is heterogeneous in terms of clinical presentation and disease progression. Cardiac involvement occurs in the minority of cases and little is known about medical management in this subgroup of NM patients. We report a rare case of heart failure (HF) in a patient with adult-onset NM in whom ivabradine proved to be able to dramatically improve the clinical picture.

Case presentation

We report a case of a 37-year-old man with adult-onset NM, presenting with weakness and hypotonia of the proximal limb muscles and shoulder girdle, severely limiting daily activities. He developed progressive HF over a period of 6 months while attending a rehabilitation program, with reduced left ventricular ejection fraction (LVEF = 20%), manifested by dyspnea and signs of systemic congestion. The patient was started HF therapy with enalapril, carvedilol, spironolactone and loop diuretics. Target HF doses of these drugs (including carvedilol) were not reached because of symptomatic hypotension causing a high resting heart rate (HR) ≥70 beats per minute (bpm). Further deterioration of the clinical picture occurred with several life-threatening arrhythmic episodes requiring external defibrillation. An implantable cardioverter defibrillator (ICD) was then implanted. Persistent high resting HR was successfully treated with ivabradine with HR lowering from 90 bpm to 55 bpm at 1 month follow up, LVEF rising to 50% at 3 month follow up and to 54% at 2,5 year follow up. To date no more hospitalizations for heart failure occurred. A single hospitalization due to aspiration pneumonia required insertion of a tracheostomy tube to protect airways from further aspiration. At present, the patient is attending a regular rehabilitation program with net improvement in neuromotor control and less limitations in daily activities.

Conclusions

HF is a rare feature of NM, but it can negatively influence prognosis. Conventional HF therapy and/or heart transplant are the only reasonable strategy in these patients. Ivabradine is a useful, effective and safe drug for therapy in NM patients with HF and should be considered when resting HR remains high despite beta-blockers’ full titration or beta-blockers’ underdosing due to intolerance or side effects.

[Treatability of sporadic late onset nemaline myopathy]

Sporadic late onset nemaline myopathy (SLONM) is an extremely rare disorder which can be associated with monoclonal gammopathy of unclear significance (MGUS). Clinically SLONM appears mostly after the fourth decade of life as rapidly progressing tetraparesis, respiratory insufficiency and features, such as dropped head syndrome, facial and bulbar involvement. Diagnosis is confirmed by muscle biopsy with detection of nemaline bodies and also frequently lobulated fibres. Immunosuppressant and immunomodulating therapies have been shown to be ineffective but clinical improvement accompanied by disappearance of monoclonal gammopathy and even nemaline bodies was reported following autologous stem cell transplantation and chemotherapy with melphalan. This article presents the case of a 53-year-old man with a 4-year history of SLOMN with MGUS in which administration of intravenous immunoglobulin therapy (IVIG) was not successful in reversing gammopathy, histopathological changes or clinical symptoms.

Sporadic late onset nemaline myopathy and immunoglobulin deposition disease

INTRODUCTION

In monoclonal gammopathy, organ dysfunction can occur due to deposition of immunoglobulin fragments. A rare form of acquired myopathy often associated with monoclonal gammopathy is sporadic late onset nemaline myopathy (SLONM), which is characterized by nemaline rods in myofibers. The pathogenetic link between monoclonal gammopathy and SLONM has not yet been elucidated.

METHODS

Case report of a patient with monoclonal gammopathy who developed a progressive myopathy, finally diagnosed as SLONM.

RESULTS

A muscle biopsy showed mild myopathic changes. A second biopsy 1 year after clinical onset demonstrated deposition of immunoglobulin light and heavy chains and the presence of nemaline rods. The patient experienced marked improvement of muscle strength after autologous stem cell transplantation and treatment with bortezomib, a therapy that is known to be effective in light chain deposition disease.

CONCLUSIONS

We speculate that deposition of light and heavy chains, rather than nemaline bodies, has myotoxic effects on skeletal muscle.

Adult nemaline myopathy with trabecular muscle fibers

The term "trabecular myopathy" has been used to designate a syndrome resembling limb-girdle muscular dystrophy in which the predominant pathological feature is an abundance of lobulated or trabecular muscle fibers. However, the validity of this nosological entity has not been verified. Herein we describe a 63-year-old man with a severe, progressive myopathy who exhibited the typical pathological features of both trabecular myopathy and nemaline myopathy in association with a biclonal gammopathy. In this case, adult-onset nemaline myopathy was probably the primary disease process. The diagnostic significance of trabecular muscle fibers remains uncertain.

Camptocormia in a Patient with Parkinson Disease and a Myopathy with Nemaline Rods

Camptocormia, also referred to as bent spine, is a gait disorder characterized by hyperflexion of the thoracolumbar spine that develops in recumbent position while walking and that disappears in supine position. Myopathy is one of the frequent causes of camptocormia. A 77-yr-old male patient who was followed up with the diagnosis of rheumatoid arthritis for 2 yrs was admitted with progressive gait deterioration. Hyperflexion of trunk, disappearing in supine position, was detected and diagnosed as camptocormia. He also exhibited the signs of parkinsonism. A paraspinal muscle biopsy showed myopathy with rods in many muscle fibers. Camptocormia in this patient may be attributable to the myopathic weakness of thoracolumbar paraspinal muscles. The normal biceps brachii muscle biopsy refers to the isolated affection of paraspinal muscles in this patient. A camptocormia (bent spine) case of myopathy with nemaline rods associated with Parkinson disease is presented.

Nemaline myopathy: a possible late complication of Hodgkin’s disease therapy

Patients who have undergone "mantle" field irradiation for Hodgkin's disease may develop symptomatic muscle atrophy in the treatment portal. This complication has received only scant attention in the clinical literature and its pathologic substrate has not been elucidated. We report the finding of nemaline myopathy in the previously irradiated and atrophic trapezius muscle of such a patient. Biopsy of clinically uninvolved gracilis muscle outside of the radiation portal revealed normal histology and ultrastructure. We are unaware of previous reports documenting such a phenomenon, which suggests that nemaline myopathy may evolve as a radiation-related disorder.

Adult-onset nemaline myopathy: Another cause of dropped head

A 59-year-old man with severe neck extensor weakness had findings diagnostic of nemaline myopathy on muscle biopsy. Review of the literature shows that dropped head occurs in nearly half of the patients with adult-onset nemaline myopathy. Other leading causes of dropped head syndrome are amyotrophic lateral sclerosis, myasthenia gravis, and isolated neck extensor myopathy.

Nemaline myopathy: current concepts. The ENMC International Consortium and Nemaline Myopathy

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