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ORIGINAL ARTICLE Table of Contents   
Year : 2008  |  Volume : 51  |  Issue : 4  |  Page : 474-480
Congenital myopathies: A clinicopathological study of 25 cases


1 Department of Pathology, All India Institute of Medical Sciences, New Delhi, India
2 Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, India
3 Department of Neurology, All India Institute of Medical Sciences, New Delhi, India

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   Abstract 

Objective: Congenital myopathies are rare. Through this article, the authors want to present a clinicopathological analysis of 25 new cases. Materials and methods: The clinical data of patients who were diagnosed with congenital myopathy between 2001 and 2006 was retrieved. Muscle biopsies were processed for H&E staining, enzyme histochemistry, and immunohistochemistry. Biopsies were also processed for ultrastructural analysis. Results: During a period of 6 years, 1.12% of the muscle biopsies were diagnosed as congenital myopathies. The most common congenital myopathy was central core disease followed by nemaline rod myopathy and multi-mini core disease. Clinically, they have variable features. The final diagnosis was made with the help of enzyme histochemistry and ultrastructural features. Conclusion: This study emphasizes the importance of enzyme histochemistry and electron microscopic examination in the diagnosis of congenital myopathies especially in the absence of genetic studies.

Keywords: Clinicopathological, congenital myopathy, enzyme histochemistry, muscle biopsy, ultra structure

How to cite this article:
Jain D, Sharma MC, Sarkar C, Gulati S, Kalra V, Singh S, Bhatia R. Congenital myopathies: A clinicopathological study of 25 cases. Indian J Pathol Microbiol 2008;51:474-80

How to cite this URL:
Jain D, Sharma MC, Sarkar C, Gulati S, Kalra V, Singh S, Bhatia R. Congenital myopathies: A clinicopathological study of 25 cases. Indian J Pathol Microbiol [serial online] 2008 [cited 2020 Feb 27];51:474-80. Available from: http://www.ijpmonline.org/text.asp?2008/51/4/474/43734



   Introduction Top


The term congenital myopathies (CMs) was introduced into scientific literature in 1956 [1] when Shy and Magee described a new congenital non progressive myopathy, which was later termed central core disease (CCD). [2],[3] Within a few years after the first description of CCD, numerous new myopathies like centronuclear myopathy (initially termed as myotubular myopathy [4] and later became familial centronuclear myopathy) [5] nemaline myopathy, [6] myopathy with myogranules, [7] multicore, [8] minicore, [9] and focal loss of cross striations [10] were described. Dubowitz [11] coined the term new myopathies, which was soon replaced by CMs. The CMs are a group of neuromuscular disorders, mostly occurring in childhood but occasionally of adult onset, which occur chiefly in a familial fashion but occasionally occur in a sporadic fashion. They are often of slow progression, but exceptionally can have more rapid course. They show disease specific structural changes in the muscle, which are detected by enzyme histochemistry and electron microscopy but sometimes with immunohistochemistry. [12] We report a series of 25 cases of CMs that, to the best of our knowledge, is the second largest series from India. Earlier, 100 cases of congenital myopathy were reported from south India by Gayatri et al . in an abstract [Neuromuscular disorders 2006;16:S108].


   Materials and Methods Top


The muscle biopsies received in the Department of Pathology of this hospital between January 2001 and December 2006 were reviewed and cases diagnosed as congenital myopathies were included in this study. The clinical data was retrieved from the hospital files and muscle biopsies were reviewed. All muscle biopsies had been received in a fresh state without any fixative from vastus lateralis of quadriceps and divided into three portions. One portion was snap frozen in liquid nitrogen after putting in isopentane. Sections of 6 in thickness were cut for routine hematoxylin and eosin (H and E) staining, enzyme histochemistry, and immunohistochemistry whenever needed to exclude other conditions. The following antibodies were used: dystrophin 1, 2, 3 (dil 1:5), sarcoglycans α, β, γ, δ (dil 1:50), emerin (dil 1:25), Lamin A/C (dil 1:25), dysferlin (Hamlet, 2, dil 1:25), and merosin (dil 1:50). All antibodies were obtained from M/s Novacastra, UK. Both enzymatic and non enzymatic histochemical stains were done, which included modified Gomori trichrome (MGT), periodic acid Schiff (PAS), oil red O, ATPase at pH 9.6, 4.6, and 4.3, nicotinamide adenine dinucleotide-tetrazolium reductase (NADH TR), succinyl dehydrogenase (SDH) alone as well as combined with cytochrome oxidase (Cox with SDH), myophosphorylase, amylopectinase phosphofructokinase (PFK), and adenylate deaminase. The second portion of the muscle biopsy was routinely processed and paraffin embedded. Sections were stained with H&E. A special stain, Masson trichrome (MT), was done to demonstrate the degree of endomysial and perimysial fibrosis. The third piece was fixed in 2.5% glutaraldehyde in 0.1 M phosphate buffer saline for electron microscopy, post-fixed with 1% osmic acid, and embedded in epoxy resin. Ultra-thin sections were double stained with uranyl acetate and lead citrate and examined under a transmission electron microscope (TEM, Morgagni 268, Holland).


   Results Top


During a period of 6 years (January 2001-December 2006), 2215 muscle biopsies were received in our laboratory, out of which 25 (1.12%) were diagnosed as congenital myopathies. The distribution of various CMs is shown in [Table 1]. Based on structural changes in the myofibers detected on histochemistry and ultrastructural examination, CMs are broadly categorized into two groups: (1) structured CMs that show structural changes in the muscle fibers (21 cases) and (2) unstructured that do not show changes [4 cases of congenital fiber type disproportion (CFTD)]. The most common CM is central core disease (24.0%) followed by nemaline rod myopathy (NM), and multi-mini core disease (MMD) each comprising 20.0%, CFTD comprised 16.0%, centronuclear myopathy (CNM) comprised 12.0%, and desmin-related myopathy (DRM)/desminopathies comprised 8.3%.

Clinical features

The salient features of CMs are shown in [Table 2].

The age at diagnosis ranged from newborn to 30 years old with a mean age of 6.5 years old. In all patients (100%), symptoms started in the first decade of life and in 14 patients (82.3%) presentation was at the time of birth. The most common symptoms and signs were difficulty in running and getting up (41.1%), generalized hypotonia in 5 patients (29.4%) [Figure 1a]; facial dysmorphism in 4 patients (23.5%) [Figure 1b]; high-arched palate in 2 patients (11%), and ptosis in 1 patient (5.88%). Both patients of desmin-related myopathy/ desminopathies were in the third decade of life, however, the onset of disease was at childhood. One patient was clinically suspected to be a case of Beckers muscular dystrophy who presented with proximal muscle weakness. This patient was reported in greater detail. [13] The patient had a thin build with generalized thinning of all muscles [Figure 1c]. None of these patients showed cardiac involvement. A family history of a similar illness was present in 2 cases (one patient of CCD had a similar history in the mother and in 1 patient with MMD the grandfather was affected). Creatine kinase levels were either normal or mildly elevated. An electromyography (EMG) was done in 14 patients, of which 10 showed myopathic changes, 3 were normal, and 1 was suggestive of neurogenic atrophy.

Pathological examination

H&E stained sections revealed maintained fascicular architecture in all cases. There was minimal variation in fiber size diameter without any degenerative and regenerative activities. Inflammation, endomysial, and perimysial fibrosis was not present except in one case of CNM (Case 9). All three cases of CNM showed central localization of nuclei in a significant number of fibers [Figure 2]. Intracytoplasmic, eosinophilic, and basophilic inclusions were seen in the case of DRM and NM; however, rimmed vacuoles were seen in the case of DRM but not in the case of NM. In the case of NM, these inclusions were evident in the formalin fixed tissue sections in three cases only but were better demonstrated on MGT staining as red granular material and were immunoreactive to α actinin. Ultrastructurally, there were subsarcolemmal and at places central accumulation of rod shaped structures similar to Z band material [Figure 3]. Inclusions of DRM were stained greenish with MGT and were immunoreactive to desmin. Ultrastructurally, both granulofilamentous and cytoplasmic bodies were identified with radiating intermediate filaments, which were immunolabelled with gold particles [Figure 4].

Oxidative histochemical stains (NADH-TR and SDH) showed unstained areas (core formation) in 11 cases. In 6 of these cases, cores appeared as well-defined punched out areas in Type I fibers usually central but occasionally slightly eccentric in locations. The number varied from one to three per fiber and these cores extended from sarcomeres to sarcomeres in the longitudinal sections. In 5 cases of MMD, these cores were multiple, smaller in size, and not well defined [Figure 5]. All cases of CCD and MMD showed Type I fiber predominance. An ultrastructural examination showed structured cores in 3 cases and both unstructured and structured cores in the other 3 cases of CCD. Structured cores showed streaming of Z bands without destruction of sarcomeres in contrast to unstructured cores, which were characterized by the disorganization of sarcomeres. All 3 cases of MMD showed unstructured cores [Figure 5]. CNM was characterized by the internalization of the nuclei in a significant number of fibers. There was a variation in fiber size in one case while the other two cases were associated with CFTD and showed a smaller diameter of fibers and predominance of Type I fibers. In addition, 4 cases had isolated CFTD without nuclear changes. Three of these cases showed predominance and hypoplasia of Type I fibers [Figure 6] while the other had Type 2 fiber predominance and hypoplasia.


   Discussion Top


Congenital myopathies are a group of neuromuscular disorders characterized by the early onset of slow progression or non progression. Depending upon the age of onset, the child may present as a floppy infant or with arthrogryposis. However, the presentation is nonspecific and clinically one cannot readily distinguish between the various subtypes. Based on changes in the myofibers, they are classified into two broad categories: structured CM and unstructured CM. Based on morphology, 40 different conditions are identified. Some of them are classic while others are accepted or doubtful conditions. [14] The major progress in recent years has been the identification of the causative genes for many congenital myopathies. The purpose of this study was to delineate the clinical features of the Indian cohort of congenital myopathies from 2001 to 2006.

During this period of 6 years, 2215 muscle biopsies were received in our laboratory for various reasons and 25 cases were diagnosed as CMs, thus comprising 1.12% of all muscle diseases. Central core disease was the most common (24%) followed by multi-mini core disease and nemaline rod disease (20% each), congenital fiber type disproportion (16%), central nuclear myopathy (12%), and desminopathies or desmin-related myopathies (8%). Congenital myopathies occur frequently in a familial manner, with onset mostly during infancy and occasionally during childhood, but rarely in adulthood. [12] In this study, more than 1 patient with a congenital myopathy was found in 3 families (Cases 5, 12, and 15). Two of our patients (Cases 9 and 16) presented in adulthood, but the onset of the disease was in childhood. Clinical features overlap between the different common forms of CMs in this study. CCD is a rare congenital myopathy, with high inter- and intra-familial phenotype variability. It is a dominantly inherited neuromuscular disorder characterized by areas with reduced oxidative activity running along the longitudinal axis of the muscle fiber. Clinical signs include hypotonia, delayed motor milestones, proximal muscle weakness, and skeletal anomalies such as hip dislocation, scoliosis, and foot deformities. [15] In our series, patients with CCD presented with proximal muscle weakness and hypotonia. Although most studies have confirmed the association between CCD and mutations in the RYR1 gene, it is not present in each case. [16] The diagnosis of CCD depends on the presence of typical histopathological findings on the muscle biopsy in combination with suggestive clinical features. Recently, the role of MRIs in the diagnosis of CCD has been emphasized. [17] Jungbluth, et al. reported muscle MRI findings of 11 patients from 8 families with RYR1 mutations who had clinical features of a congenital myopathy with a wide variety of associated histopathological changes. They concluded that patients with RYR1 -related congenital myopathies have a recognizable pattern of muscle involvement irrespective of the variability of associated histopathological findings. They proposed that muscle MRI may supplement clinical assessment and aid in selection for genetic tests particularly in patients with non diagnostic or equivocal histopathological features. [17] Histochemical staining of muscle biopsy samples shows the absence of oxidative and glycolytic enzymatic activity from central core regions. [3] Oxidative histochemical stains (NADH-TR and SDH) showed core formation in 10 cases. In 6 of these cases, cores appeared as well-defined punched-out areas in Type I fibers. Typical findings on the electron microscopy include the reduction or absence of mitochondria, variable degrees of myofibrillar disorganization, and accumulation of abnormal Z band material within the usually sharply demarcated core area. [15] Similarly, we found streaming of Z-bands with myofibrillar disorganization in core areas. Multicore myopathies have the same histochemical and ultrastructural appearance as central cores but are not localized to Type 1 fibers. Clinical features associated with minicores on the muscle biopsy are markedly heterogeneous. However, spinal rigidity, scoliosis, and respiratory impairment are the hallmark of the classic phenotype of MMD. [18] In our series, patients presented early in life with generalized hypotonia and delayed milestones. A high-pitched voice and myopathic facial features are common, occasionally associated with a high-arched or cleft palate. [18] A high-arched palate and myopathic facies were identified in Case 14. On histopathologic examination, cores may vary in size and morphology, to some extent depending on the genetic background. SEPN1 -related MMD is typically associated with minicores, whereas multicores are more commonly seen in MMD related to mutations in the RYR1 gene. [19] Although the presence of cores is a prerequisite for the diagnosis of MMD, it is not pathognomonic of the disease as it can be seen in other conditions also. [20] On electron microscopy, minicores present as areas of myofibrillar disruption and paucity of mitochondria, often with degeneration of the sarcomeres. [21] We did find sarcomeric disruption in core areas. Respiratory impairment is the main prognostic factor in classic MMD. Fortunately, our three cases did not show any respiratory involvement.

The most frequent clinical features of centronuclear myopathy are delayed motor milestones, facial and generalized muscle weakness, ptosis, and ophthalmoparesis. The most prominent histopathological features consist of a high frequency of centrally located nuclei in the muscle fibers and predominance and hypotrophy of Type 1 fibers. There are autosomal recessive and autosomal dominant forms, which have a relatively benign course. The most severe is the X-linked recessive form, which usually manifests in neonates. [12] Of the three patients in the present series, the latter type was not recognized. Facial dysmorphic features were present in two patients and a third patient presented at the age of 21 years; however, his history dates back to childhood. In the present series, patients with CFTD presented early in their lives and had relatively severe phenotypes. Histologically, CFTD is characterized by smaller Type I fibers. In the present series, we found 2 cases of CFTD associated with centrally placed nuclei. In addition, four cases had isolated CFTD without nuclear changes. Three of these cases showed predominance and hypoplasia of Type I fibers while the other had Type 2 fibers predominance and hypoplasia. Centrally placed nuclei in CFTD have been reported earlier either at the time of the first diagnosis or in a repeat biopsy. [22] Dysmorphic features were present in only one case (Case 10). Recently, clinical features of CFTD have been compared with congenital myopathy with Type I fiber predominance and found that the frequency of dysmorphic features is relatively less in congenital myopathy with Type I fiber predominance. [23] It needs to be elucidated whether congenital myopathy with Type I fiber predominance is a distinct entity.

Nemaline myopathies are now considered to be a genetically diverse group of congenital myopathies marked by the excessive formation of rods or nemaline bodies within the muscle fibers. Of the four broad clinical types of nemaline myopathy, our patient probably fits into the congenital or classic form. Clinically, the nemaline myopathies present with proximal or generalized muscle weakness including facial muscles. This results in a characteristic myopathic facies. The formation of rods within muscle fibers is the hallmark of nemaline myopathies. The nemaline bodies represent a surplus of Z-band material predominantly composed of α actinin. The various gene loci from their defective proteins have been localized as α-tropomyosin (TPM3) to 1q 21-23, Nebulin (NEB) to 2q 21.2.22, sarcomeric actin (ACTA1) to 1q42p, β-tropomyosin (TPM 2) to 9p13.2, and troponin T1 (TNNT1) to 19q 13.4. [24],25],[26]

Only two patients of DRM/desminopathies have been found in the present study and both were diagnosed at an older age as compared with other patients with CMs. One of them was thin, lean, and had generalized weakness and wasting of muscles. He also had a history of repeated respiratory infections. The other patient was suspected to be a case of Beckers muscular dystrophy. Distal muscle weakness, cardiac involvement, normal or mildly raised CK levels along with histopathological findings of rimmed vacuoles and eosinophilic inclusions are typical of desminopathies. The patients of α-B-crystallinopathy have similar presentation but in addition have premature cataract. The latter was not found in any of these patients. Desmin-related myopathies are characterized by abnormal accruing of desmin intermediate filaments within the muscle fibers. [27] The case described in the present series appears to be sporadic or caused by a de novo mutation. Morphologically, the muscle biopsy shows dystrophic changes, inclusions in the myofibrils, and rimmed vacuoles. Although rimmed vacuoles within the myofibrils are seen in desmin-related myopathies, they are not pathognomonic of this group of diseases only. They are also seen in inclusion body myopathies, distal myopathies, and myosinopathies, another form of surplus myopathies. Ultrastructurally, they can not be differentiated from each other as changes are similar. Therefore, genetic studies are necessary for an accurate diagnosis.

In contrast to other muscular dystrophies where there is an absence or reduction of muscle proteins, so called "minus protein myopathies", this group of neuromuscular disorders is characterized by the excess or accruing of abnormal or mutated proteins and belong to "protein surplus or aggregate myopathies". [28] Many of the congenial myopathies belong to this category.


   Conclusion Top


Congenital myopathies are rarely described in Indian literature. This study from India highlights the importance of enzyme histochemistry and ultrastructural examination in the diagnosis of congenital myopathies in the absence of the availability of genetic studies.

 
   References Top

1.Magee KR, Shy GM. A new congenital non-progressive myopathy. Brain 1956;79:610-21.  Back to cited text no. 1    
2.Bethlem J, Posthumus-Meyjes FE. Congenital nonpressive central core disease of Shy and Magee. Psy Neurol Neurochir Ant 1970;63:246.  Back to cited text no. 2    
3.Dubowitz V, Pearse AG. Oxidative enzymes and phosphorylase in central-core disease of muscle. Lancet 1960;2:23-4.  Back to cited text no. 3    
4.Spiro AJ, Shy GM, Gonatas NK. Myotubular myopathy: Persistence of fetal muscle in an adolescent boy. Arch Neurol 1966;14:1-14.  Back to cited text no. 4    
5.Sher JH, Rimalovski AB, Athanassiades TJ, Aronson SM. Familial myotubular myopathy: A clinical, pathological, histochemical, and ultrastructural study. J Neuropathol Exp Neurol 1967;26:132-3.  Back to cited text no. 5    
6.Shy GM, Engel WK, Somers JE, Wanko T. Nemaline myopathy: A new congenital myopathy. Brain 1963;86:793-810.  Back to cited text no. 6    
7.Conen PE, Murphy EG, Donohue WL. Light and electron microscopic studies of "myogranules" in a child with Hypotonia and muscle weakness. Can Med Assoc J 1963;89:983-6.  Back to cited text no. 7    
8.Engel AG, Gomez MR, Groover RV. Multicore disease. A recently recognized congenital myopathy associated with multifocal degeneration of muscle fibers. Mayo Clin Proc 1971;46:666-81.  Back to cited text no. 8    
9.Currie S, Noronhe M, Hariman D. Minicore disease. 3 rd International Congress on Muscle Diseases. Amsterdam: Excerpta Medica; 1974.p. 12.  Back to cited text no. 9    
10.Engel WK. Central core disease and focal loss of cross striation. In: Goldenshohn ES, Appel SH, editors. Scientific approaches to clinical neurology. Philadelphia: Lea and Febiger; 1977. p. 1555-71.  Back to cited text no. 10    
11.Dubowitz V. The "new" myopathies. Neuropediatric 1969;1:137-48.  Back to cited text no. 11    
12.Nonaka I. Clinical and pathologic aspects of congenital myopathies. Neurol J Southeast Asia 2001;6:99 -106.   Back to cited text no. 12    
13.Sridhar E, Sharma MC, Sarkar C, Singh S, Das T. Desmin-related myopathy: report of a rare case. Neurol India 2005;53:229-31.  Back to cited text no. 13  [PUBMED]  Medknow Journal
14.Goebel HH. Congenital myopathies. Semin Pediatr Neurol 1996;3:152-61.  Back to cited text no. 14    
15.Dubowitz V, Roy S. Central core disease of muscle: Clinical, histochemical and electron microscopic studies of an affected mother and child. Brain 1970;93:133-46.  Back to cited text no. 15    
16.Romero NB, Monnier N, Viollet L, Cortey A, Chevallay M, Leroy JP, et al. Dominant and recessive central core disease associated with RYR1 mutations and fetal akinesia. Brain 2003;126:2341-9.  Back to cited text no. 16    
17.Jungbluth H, Davis MR, Muller C, Counsell S, Allsop J, Chattopadhyay A, et al. Magnetic resonance imaging of muscle in congenital myopathies associated with RYR1 mutations. Neuromuscul Disord 2004;14:785-90.  Back to cited text no. 17    
18.Jungbluth H, Sewry C, Brown SC, Manzur AY, Mercuri E, Bushby K, et al. Minicore myopathy in children: A clinical and histopathological study of 19 cases. Neuromuscul Disord 2000;10:264-73.  Back to cited text no. 18    
19.Ferreiro A, Monnier N, Romero NB, Leroy JP, B φnnemann C, Haenggeli CA, et al. A recessive form of central core disease, transiently presenting as multiminicore disease, is associated with a homozygous mutation in the ryanodine receptor type 1 gene. Ann Neurol 2002;51:750-9.   Back to cited text no. 19    
20.Goebel HH. Multi-mini core disease. In: Karpanti G, editor. Structural and molecular basis of skeletal muscle diseases. Basel: ISN Neuropath Press; 2002. p. 68-9.  Back to cited text no. 20    
21.Dubowitz V, Sewry CA. Muscle biopsy - A practical approach. 3 rd ed. London: WB Saunders; 2006.  Back to cited text no. 21    
22.Gayathri N, Das S, Vasanth A, Devi MG, Ramamohan Y, Santosh V, et al. Centronuclear myopathy--morphological relation to developing human skeletal muscle: A clinicopathological evaluation. Neurol India 2000;48:19-28.  Back to cited text no. 22  [PUBMED]  Medknow Journal
23.Na SJ, Kim WK, Kim TS, Kang SW, Lee EY, Choi YC. Comparison of clinical characteristics between congenital fiber type disproportion myopathy and congenital myopathy with type 1 fiber predominance. Yonsei Med J 2006;47:513-8.  Back to cited text no. 23    
24.Bouldin AA, Parisi MA, Laing N, Patterson K, Gospe SM Jr. Variable presentation of nemaline myopathy: Novel mutation of alpha actin gene. Muscle Nerve 2007;35:254-8.  Back to cited text no. 24    
25.Lehtokari VL, Pelin K, Sandbacka M, Ranta S, Donner K, Muntoni F, et al. Identification of 45 novel mutations in the nebulin gene associated with autosomal recessive nemaline myopathy. Hum Mutat 2006;27:946-56.  Back to cited text no. 25    
26.Wallgren-Pettersson C, Laing NG. 138 th ENMC Workshop: Nemaline Myopathy, 20-22 May 2005, Naarden, The Netherlands. Neuromuscul Disord 2006;16:54-60.  Back to cited text no. 26    
27.Olive M, Goldfarb L, Moreno D, Laforet E, Dagvadorj A, Sambuughin N, et al. Desmin-related myopathy: Clinical, electrophysiological, radiological, neuropathological and genetic studies. J Neurol Sci 2004;219:125-37.  Back to cited text no. 27    
28.Goebel HH, Borchert A. Protein surplus myopathies and other rare congenital myopathies. Semin Pediatr Neurol 2002;9:160-70.  Back to cited text no. 28    

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Correspondence Address:
Mehar C Sharma
Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110 029
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.43734

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    Figures

  [Figure 1a], [Figure 1b], [Figure 1c], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
 
 
    Tables

  [Table 1], [Table 2]

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[Pubmed] | [DOI]



 

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