Skeletal muscle pseudohypertrophy in primary amyloidosis

Wild-type Transthyretin Amyloid Myopathy With an Inclusion Body Myositis Phenotype

Senile systemic amyloidosis (SSA), or wild-type transthyretin (wtATTR) amyloidosis, is associated most commonly with cardiomyopathy and carpal tunnel syndrome. SSA-associated skeletal myopathy is rare. We describe the case of a patient with SSA who exhibited asymmetric quadriceps and finger flexor weakness, a phenotype usually seen in inclusion body myositis.

Chronic myopathy due to immunoglobulin light chain amyloidosis

Amyloid myopathy associated with a plasma cell dyscrasia is a rare cause of muscle hypertrophy. It can be a challenging diagnosis, since pathological findings are often elusive. In addition, the mechanism by which immunoglobulin light-chain deposition stimulates muscle overgrowth remains poorly understood. We present a 53-year old female with a 10-year history of progressive generalized muscle overgrowth. Congo-red staining and immunohistochemistry revealed perivascular lambda light chain amyloid deposits, apparent only in a second muscle biopsy. The numbers of central nuclei and satellite cells were increased, suggesting enhanced muscle progenitor cell formation. Despite the chronicity of the light chain disease, the patient showed complete resolution of hematologic findings and significant improvement of her muscle symptoms following autologous bone marrow transplantation. This case highlights the importance of early diagnosis and therapy for this treatable cause of a chronic myopathy with muscle hypertrophy.

The neuromuscular manifestations of amyloidosis

Amyloidosis is a systemic disease that may be acquired or hereditary and which results in the deposition of amyloid fibrils in a variety of tissues causing their progressive dysfunction. Although the clinical presentation often is dominated by cardiac or renal failure, peripheral neuropathy may be a significant or the initial manifestation, resulting in presentation to the neurologist. Diagnosis often is challenging and may require multiple diagnostic procedures, including more than one biopsy. Acquired and hereditary amyloidosis can be definitively distinguished from one another only by immunohistochemical staining or molecular genetic testing. Treatment remains a challenge, although chemotherapy and autologous stem cell transplantation offer hope for those with primary systemic amyloidosis, whereas liver transplantation is effective for some forms of hereditary amyloid neuropathy. Much less commonly, myopathy may be a clinically significant manifestation of amyloidosis.

Amyloid-associated muscle pseudohypertrophy and multiple myeloma in a man with hypernephroma

Amyloidosis is known to occur both in renal adenocarcinoma and multiple myeloma. This paper describes a 52-year-old man who developed multiple myeloma and widespread amyloidosis after surgical removal of a hypernephroma. Multiple myeloma presented with osteolytic bone lesions and slight bone marrow plasmocytosis. Both kappa light chains and monoclonal IgG were secreted. Amyloidosis was seen as muscle pseudohypertrophy with wood-hard masses of amyloid in shoulders, girdle, buttocks and proximal limbs. Macroglossia was impressive and swelling of submandibular structures and the floor of the mouth was marked. Knowing the peculiar immunological potency of hypernephroma, attention is called to associations between renal carcinoma and monoclonal gammopathies, including amyloidosis.

Generalized muscle pseudo-hypertrophy and stiffness associated with the myotilin Ser55Phe mutation: a novel myotilinopathy phenotype?

Myotilinopathies are a group of muscle disorders caused by mutations in the MYOT gene. It was first described in two families suffering from limb girdle muscle dystrophy type 1 (LGMD 1A), and later identified in a subset of dominant or sporadic patients suffering from myofibrillar myopathy, as well as in a family with spheroid body myopathy. Disease phenotypes associated with MYOT mutations are clinically heterogeneous and include pure LGMD forms as well as late-onset distal myopathies. We report here on a 53-year-old male suffering from a unique clinical profile characterized by generalized symmetrical increase in muscle bulk leading to a Herculean appearance. Muscle weakness and stiffness in the lower extremities were the patient's main complaints. Muscle MRI showed extensive fatty infiltration in the thigh and leg muscles and a muscle biopsy showed a myofibrillar myopathy with prominent protein aggregates. Gene sequencing revealed a Ser55Phe missense mutation in the myotilin gene. The mutation was identified in his older brother, who presented a mild hypertrophic appearance and had a myopathic pattern in EMG, despite not presenting any of the complaints of the proband and having normal muscle strength. This finding, and his deceased father and paternal aunt's similar gait disorders, suggest that this is in fact a new autosomal dominant kindred. The present observations further expand the spectrum of clinical manifestations associated with mutations in the myotilin gene.

Immunoglobulin light-chain (AL) amyloidosis with myasthenic symptoms and echocardiographic features of dilated cardiomyopathy

Myasthenic symptoms and the echocardiographic findings of dilated cardiomyopathy are very rare in primary AL amyloidosis. We report a 59-year-old man with dyspnea on effort and weakness after exercise. His electrocardiogram showed ischemic heart disease and echocardiography indicated dilated cardiomyopathy. Muscle biopsy revealed amyloidosis with deposits of lambda light chain-derived amyloid within the vessel wall. Treatment with PGE1 resulted in improvement of the myasthenic symptoms. This patient indicates that myasthenic symptoms and dilated cardiomyopathy would be a unique syndrome associated with systemic AL amyloidosis involving mainly the small vessels, i.e., AL amyloid angiopathy, in the skeletal muscles and myocardium vessels.

Amyloid myopathy: characteristic features of a still underdiagnosed disease

A 62-year-old man with progressive proximal weakness underwent extensive evaluation including muscle biopsy without a clear diagnosis being established. A repeat muscle biopsy including Congo red-stained sections revealed infiltration of blood-vessel walls and endomysium with amyloid protein, as well as an unusual pattern of pathologic changes to muscle fibers. From a review of 79 cases of amyloid myopathy reported in the English-language literature, the characteristic features of this disorder are described. Congo red-stained sections of muscle biopsy viewed under fluorescent or polarized optics, and serum or urine protein immunoelectrophoresis, play an important role in the evaluation of myopathy. Amyloid myopathy should be a consideration in adults with progressive neuromuscular weakness of uncertain cause.

Amyloidotic muscle pseudohypertrophy: case report

The authors report one case of amyloidosis associated with muscular pseudohypertrophy in a 46-year-old woman, who developed weakness, macroglossia and muscle hypertrophy associated with primary systemic amyloidosis. Electromyography showed a myopathic pattern and bilateral carpal tunnel syndrome. The muscle biopsy presented with a type I and II fiber hypertrophy and infiltration of amyloid material in the interstitious space and artery walls. She underwent bone marrow transplantation with stabilization and subjective improvement of the clinical picture.

Electrophysiologic findings in amyloid myopathy

Myopathy is an uncommon manifestation of systemic amyloidosis. A retrospective chart review of 17 patients seen between 1975 and 1997 with biopsy-proven amyloid myopathy was performed to characterize the electrophysiologic features. Nerve conduction study abnormalities occurred in 14 of 17 patients (82%). The most common abnormality was a low peroneal and/or tibial compound muscle action potential amplitude (n = 9). Mild abnormalities also occurred in seven other nerves. Repetitive stimulation at 2 Hz in 10 nerves was normal. Electromyography demonstrated fibrillation potentials in 69% of muscles, most frequently in the gluteus medius (90%) and paraspinals (87%). The fibrillation potentials were sparse in 60%. Short-duration, low-amplitude motor unit potentials (MUPs) were found in 72% of the muscles examined, were mild in 81%, and were more common in proximal muscles. Long-duration MUPs were found in 19% of muscles and a mixed population of MUPs in 4%. These findings are similar to those of common chronic, inflammatory myopathies.

Amyloid myopathy: an underdiagnosed entity

Amyloidosis can involve multiple organs, including kidney, heart, peripheral nerve, skin, joints, and skeletal muscle, but rarely presents as a myopathy. We studied 13 adults with muscle weakness for between 3 months and 4 years in whom the diagnosis of systemic amyloidosis was unsuspected before or until just before the time of the muscle biopsy. All muscle specimens demonstrated congophilic deposits around blood vessels and muscle fibers, some necrotic and regenerating fibers, and signs of mild denervation. Immunostains in 10 patients revealed immunoglobulin amyloidosis in 7 and gelsolin amyloidosis in 1. Apolipoprotein E co-localized with the congophilic deposits in all 10, and a C-terminal epitope of the beta-amyloid precursor protein was detected in 6. The frequency of the diagnosis of amyloid myopathy increased 10-fold when we adopted the fluorescent Congo red stain as a routine procedure in assessing muscle biopsy specimens.

Neuromyotonia and type I myofiber predominance in amyloidosis

A case of amyloidosis presented with neurormyotonia and marked predominance of type I myofibers as documented by biopsy of an enlarged anterior tibialis muscle. This likely represents conversion of type II fibers to type I from continuous neuromyotonic stimulation. This transformation is well described to occur in animal models and this case represents a unique human example. Enlarged muscles likely reflected pseudohypertrophy.

AAEM minimonograph #46: neurogenic muscle hypertrophy

Muscle hypertrophy occurs uncommonly in several neurogenic disorders including neuropathies, radiculopathies, spinal muscular atrophy, and post-polio syndrome. Its pathogenesis varies in different circumstances. In the presence of generalized myokymia and neuromyotonia (Isaacs' syndrome), symmetrical hypertrophy appears to be the result of continuous spontaneous electrical stimulation of myofibers and, in some cases, results in type 1 myofiber preponderance. Focal hypertrophy occurring with radiculopathies and mononeuropathies was associated with complex repetitive discharges (CRDs) in approximately half the cases. CRDs may play a role in the pathogenesis of myofiber hypertrophy by continuous myofiber stimulation, but in some cases, with and without CRDs, myofiber hypertrophy may be related to mechanical events. Muscle enlargement seen in old polio appears to involve a significant degree of pseudohypertrophy, although some myofiber hypertrophy occurs. The symmetrical occurrence of hypertrophy in genetically determined disorders, such as spinal muscular atrophy, and hereditary motor and sensory neuropathy types 1 and 2 may have both a genetic and a mechanical basis in addition to pseudohypertrophy in some cases.

Myopathy in primary systemic amyloidosis

OBJECTIVE

To define the natural history of primary systemic amyloidosis when muscle involvement is prominent at presentation.

METHODS

A retrospective review was carried out of all patients seen at the tertiary referral practice of the Mayo Clinic between 1 January 1960 and 31 December 1994. All patients with primary systemic amyloidosis and proof of amyloid deposits by muscle biopsy were included for analysis. No patients were lost to follow up.

RESULTS

Twelve patients were identified with amyloidosis in muscle. Muscle involvement was the most prominent symptom in patients who had widespread visceral involvement, which included the heart, peripheral nerve, and tongue. Of the 12, three had skeletal muscle pseudohypertrophy. All patients had a demonstrable dysproteinaemia by the finding of free light chain in the serum or urine, a discrete monoclonal peak on serum or urine protein electrophoresis, or a monoclonal population of plasma cells in the bone marrow. Measurement of creatine kinase was not a useful test. Of eight patients treated with chemotherapy based on alkylating agents, three responded. The median survival for the entire group was 12 months.

CONCLUSIONS

The finding of a monoclonal protein in a patient with muscle weakness is an important clue to the diagnosis of primary systemic amyloidosis. Most patients have visceral involvement outside the musculoskeletal system. A subset of patients seems to respond to systemic chemotherapy. The overall survival, however, remains poor, with most patients dying of cardiac failure. Immunoelectrophoresis of serum and urine should be a routine diagnostic test during the evaluation of myopathy of unknown cause.

Further evidence of increased risk of mortality of Parkinson's disease

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Amyloid associated muscle pseudohypertrophy: amelioration of motor dysfunction with plasmapheresis and dimethylsulphoxide

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Amyloidosis causing a progressive myopathy

A 62-year-old woman developed profound weakness secondary to a progressive myopathy associated with primary systemic amyloidosis. The characteristic apple-green birefringent amyloid deposits were demonstrated surrounding individual muscle fibers in Congo red stained sections. Electron microscopy demonstrated amyloid filaments in close apposition to muscle fibers exhibiting excessive corrugations of the sarcolemmal membrane. The pathological features of progressive amyloid myopathy associated with primary systemic amyloidosis are distinct from the intracellular amyloid deposits characteristic of sporadic inclusion body myositis and inherited inclusion body myopathy.

Muscle hypertrophy secondary to the tethered cord syndrome

Segmental muscle enlargement occurs in a variety of neurogenic conditions. We present a case with calf hypertrophy, likely produced by partial denervation and continuous neuromuscular irritability, which was caused by a tethered spinal cord that was demonstrated by MRI. Muscle MRI correlated with muscle biopsy findings in which atrophy and hypertrophy were accompanied by rimmed vacuoles.

Progressive unilateral hypertrophic myopathy: a case study

A 12-year-old girl had progressive unilateral muscle hypertrophy limited to the sole, tibialis anterior, and biceps femoris muscles. The affected muscles showed complex repetitive discharges by electromyography, necrosis and variation of fiber size upon histopathological examination, and increased metabolic activity in biochemical studies. The findings suggest a myopathic origin, but the actual cause remains unknown.

Amyloid myopathy presenting with respiratory failure

Amyloidosis is a rare cause of myopathy. Its prominent or presenting feature may be respiratory failure. Physiological measurement of transdiaphragmatic pressure and biopsy specimens of muscle show the pathological mechanism to be diaphragm weakness due to amyloid infiltration of the diaphragm rather than parenchymal lung involvement. Thus amyloid myopathy even without the typical macroglossia and muscle pseudohypertrophy should be considered as one of the neurological causes of respiratory failure.

Rheumatologic manifestations of malignancy

The relationship between rheumatologic syndromes and cancer covers a very broad array of both common and distinctly rare manifestations. This discussion has outlined some of the known relationships that do exist. A high index of suspicion by both the primary care physician and subspecialist will enhance the probability of detecting cancer in the patient who may present with rheumatologic complaints.

Myopathy in primary systemic amyloidosis

Involvement of the peripheral nervous system by amyloidosis is common. It is less well recognized that amyloid can directly infiltrate and weaken skeletal muscle. We report a case of a 73-year-old woman, known to have cardiac amyloidosis, who developed profound weakness secondary to amyloid myopathy. Review of the 8 other well documented cases in the literature has revealed a rather homogeneous syndrome. Proximal weakness, muscle stiffness, pseudohypertrophy and myalgia constitute the principal features. This syndrome usually develops in cases with well recognized generalized amyloidosis. Amyloid is deposited within the basal lamina of blood vessels and muscle fibers.

Skeletal muscle amyloid deposition in AL- (primary or myeloma-associated), AA- (secondary), and prealbumin-type amyloidosis

Amyloid deposition in the quadriceps femoris muscle was investigated in 12 cases of systemic amyloidosis including 6 of AL-(primary or myeloma-associated) type, 2 of AA- (secondary) type, and 4 of prealbumin- (familial or sporadic) types. Clinically, muscle weakness was found in 7 patients. Among the 7 patients, one of the AL-type suffered from systemic myopathy showing progressive muscular stiffness, pseudohypertrophy, and weakness. The other 6 presented with polyneuropathy. Pathologically, no amyloid was found to be deposited in the AA-type. In all of the AL- and prealbumin-types, amyloid deposition was found in the blood vessels and peri- and endomysium. The degrees of amyloid deposition were marked in one case of the AL-type, which was considered to be suffering from amyloid myopathy, moderate in one of the AL-type, and slight in the rest of the AL-type and all of the prealbumin-type. Our observations and descriptions in the literature indicate that the presence and degrees of amyloid deposition in the skeletal muscles would be related to the types of amyloid proteins in amyloidosis. It seems likely that the affinity of amyloid to the skeletal muscles is variable in AL-type, probably depending on the molecular heterogeneity of AL protein, is low in prealbumin-type, and is almost absent in AA-type.

Proximal weakness of the extremities as main feature of amyloid myopathy

Two patients with muscle weakness caused by amyloid myopathy are described. Characteristic features such as pseudohypertrophy and abnormal firmness, and tumours of muscles were absent. It is suggested that muscle weakness in amyloid myopathy is caused by layers of amyloid covering muscle fibres. In middle aged or elderly patients with proximal muscle weakness the diagnosis of amyloid myopathy should be considered.

Respiratory muscle weakness and ventilatory failure in AL amyloidosis with muscular pseudohypertrophy

Generalized muscle weakness culminating in ventilatory failure developed in a 59-year-old man with kappa light chain multiple myeloma. Physical examination demonstrated skeletal muscle enlargement, severe proximal muscle weakness, and macroglossia, consistent with amyloid-associated muscle pseudohypertrophy. Pulmonary function studies revealed a severe restrictive abnormality with a low maximal inspiratory pressure and maximal voluntary ventilation. Arterial blood gas values and chest radiographic results were normal. There was no clinical evidence of cardiac or central nervous system disease. At autopsy, skeletal muscles and diaphragm were diffusely infiltrated by amyloid. There was also multifocal deposition of amyloid in alveolar septae, esophagus, and subendocardium. This report suggests that ventilatory failure may occur as a complication of myeloma-associated (AL) amyloidosis involving the respiratory muscles.

Early sarcolemmal dysfunction in skeletal muscle amyloidosis

Weakness and stiffness appeared in a 65-year-old man affected by multiple myeloma. Muscle fibre conduction velocity was recorded in situ in the biceps brachii and found to be significantly decreased. Muscle biopsy, performed in the same muscle, showed amyloid deposition and moderate atrophy of muscle fibres, which was not sufficient to explain the reduction in muscle fibre conduction velocity. The results of the study suggest that amyloid interferes with conduction along the sarcolemma and that this plays a pathogenetic role mainly in the early stages of the disease.

In vitro myotrophic effect of serum kappa chain immunoglobulins from a patient with kappa light chain myeloma and muscular hypertrophy

Muscle hypertrophy due to enlarged muscle fibers was accompanied by kappa light chain myeloma in a 62-yr-old man. Immunofluorescence showed kappa light chain deposits around muscle fibers. We hypothesized that a circulating growth factor may be involved in the pathogeny of this muscular hypertrophy. Patient serum cultured with muscle cells showed that (a) the patient's serum exhibited a trophic effect on human muscle cells in culture, (b) this trophic effect increased the differentiation and did not influence the proliferation of human muscle cells, and (c) the fraction of the patient's serum immunoadsorbed on antihuman kappa chain antibodies exhibited the same in vitro effect on the muscle cells, whereas the fraction immunoadsorbed on antihuman lambda chain antibodies did not. These results support the hypothesis that the patient's kappa light chains have a specific enhancing effect on human muscle cell differentiation, perhaps leading to an acquired muscular hypertrophy.

Myeloma, paraproteinemias, and the skin

This review focuses on those systemic diseases or syndromes associated with monoclonal plasma cell disorders that may present with important cutaneous manifestations. Amyloidosis, POEMS syndrome, cutaneous plasmacytoma, xanthomas, benign hypergammaglobulinemic purpura of Waldenström, and scleromyxedema are emphasized.

Postpoliomyelitis muscle pseudohypertrophy

A 62-year-old patient who had had acute paralytic poliomyelitis in early childhood developed bilateral lower limb muscle pseudohypertrophy. The pseudohypertrophy was caused primarily by an enormous excess of adipose tissue replacing muscle fibers, and, in part, by work hypertrophy of muscle fibers.

Paraproteinosis and amyloidosis of the cerebral vessels and senile plaques

A case is reported of progressive dementia and a terminal picture of generalized tetaniform contractures. The relationship of the generalized tetaniform contractures to the stiff-man syndrome is discussed. Morphologically, diffuse amyloid deposition was found in the pial and cortical vessels, accompanied by amyloid deposition in the senile plaques in the cortical and cerebellar cortex. Apart from the typical staining and ultrastructural aspects of amyloid, a deposition of material was observed, corresponding in optical and electron microscopy to a paraprotein. This case demonstrated not only the relationship between the deposition of amyloid and the formation of senile plaques, but also sustains the direct connection between amyloid in senile plaques and the paraprotein substances deriving from the blood. The probable relationship between the unusual deposition of paraproteins in the vessels and nervous system and the treatment with immunoglobulins is discussed.

Infiltrating lipoma: a cause of monomelic hypertrophy

Muscle biopsy and computerized tomography indicated that unilateral enlargement of the gastrocnemius muscle in a 12-year-old girl was the result of an infiltrating lipoma. This rare condition may cause diagnostic confusion before EMG and muscle biopsy studies are performed, but it can be readily distinguished from other causes of unilateral muscle enlargement using these methods.