Clinical characteristics.

Salih myopathy is characterized by muscle weakness (manifest during the neonatal period or in early infancy) and delayed motor development; children acquire independent walking between age 20 months and four years. In the first decade of life, global motor performances are stable or tend to improve. Moderate joint and neck contractures and spinal rigidity may start in the first decade but become more obvious in the second decade. Scoliosis develops after age 11 years. Cardiac dysfunction starts between ages five and 16 years, progresses rapidly, and leads to death between ages eight and 20 years, usually from heart rhythm disturbances.

Diagnosis/testing.

Diagnosis is based on clinical findings, marginally to moderately increased serum creatine kinase levels, characteristic skeletal muscle histology, and biallelic small frameshift deletions in the exons Mex1 and Mex3 of TTN, the only gene in which pathogenic variants are known to cause Salih myopathy.

Management.

Treatment of manifestations: Care, best provided by a multidisciplinary team, includes stretching exercises and physical therapy; assistive mechanical devices for sitting and ambulation as needed; and appropriate technical aid in educational settings. Treat heart failure and cardiac arrhythmia as soon as they are evident. Cardiac transplantation may be considered for progressive dilated cardiomyopathy and heart failure refractory to medical therapy.

Prevention of secondary complications: Annual influenza vaccine and other respiratory infection-related immunizations are advised; aggressive treatment of lower respiratory tract infections.

Surveillance: Every six months from age five years: cardiac function and rhythm. Annually: respiratory function. As needed: orthopedic complications (foot deformity, joint contractures, and spinal deformity) by clinical examination and x-ray as needed.

Agents/circumstances to avoid: Ibuprofen in those with congestive heart failure.

Genetic counseling.

Salih myopathy is inherited in an autosomal recessive manner. The parents of an affected child are obligate heterozygotes (i.e., carriers of one mutated allele) and are asymptomatic. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and prenatal diagnosis for pregnancies at increased risk are possible if the pathogenic variants in the family have been identified.

Clinical Diagnosis

Salih myopathy is characterized clinically by the following:

• Muscle weakness manifesting during the neonatal period or in early infancy
• Delayed motor milestones but normal cognitive development
• Muscle weakness of limb-girdle distribution, myopathic face, variable degree of ptosis, and relative calf muscle hypertrophy
• Development of dilated cardiomyopathy between ages five and 16 years
• Major heart rhythm disturbances leading to sudden death before age 20 years

Testing

Biochemical and electrophysiologic studies

• Serum creatine kinase (CK) is marginally to moderately increased (1.5-7x normal).
• Electromyography (EMG) shows myopathic features (low-amplitude polyphasic potentials of short duration).
• Nerve conduction studies (NCS) are normal.

Muscle biopsy. The following findings help distinguish Salih myopathy from congenital muscular dystrophy (CMD) and other congenital myopathies.

• Histology of skeletal muscle reveals a pattern compatible with congenital myopathy (Figure 1): mild variation in fiber size, abundant centrally located nuclei, no increase in connective tissue before age six years, and mild endomysial fibrosis after age six years.
  Oxidative stains reveal multiple small lesions of reduced or absent oxidative activity with poorly defined boundaries.
  Myofibrillar ATpase staining shows remarkable type 1 fiber predominance (>90%). In one individual massive muscle fiber loss was seen in a second biopsy taken at age ten years [Carmignac et al 2007].
• Immunohistochemistry of skeletal muscle shows normal expression of dystrophin, laminin α2 chain (merosin), integrin α7, α - and β-dystroglycan, desmin, emerin, and the sarcoglycans α (adhalin), β, γ, and δ.
• Electron microscopy of skeletal muscle (Figure 2) highlights the “minicore-like” lesions seen on histology and reveals multiple foci of sarcomere disruption and mitochondria depletion.

Figure 1.

Skeletal muscle histology of two children with Salih myopathy taken at age four years (A and D) and 14 years (B and C). A and D. The early biopsy shows (A) increased fiber size variability, abundant centrally located nuclei (CNLs) but no endomyseal fibrosis (more...)

Figure 2.

Longitudinal electron microscopy section of skeletal muscle taken at age ten years reveals focal disruptions of sarcomeric structures (arrows), Z-disk abnormalities including focal loss of dark Z-disk material, and early dissolution of I-band filaments (more...)

Heart muscle biopsies (taken from two individuals) showed increased interstitial fibrosis compatible with dilated cardiomyopathy [Carmignac et al 2007]. Oxidative staining was normal without focal oxidative defects or significant disarray of the cardiomyocyte structure in contrast to the classic observation in hypertrophic cardiomyopathy.

Electrocardiography (ECG) is very helpful in signaling the occurrence of cardiac involvement. Left axis deviation (left anterior fascicular block) can be seen as early as age four years (Figure 3). With the onset of dilated cardiomyopathy (between ages 5 and 16 years), major rhythm disturbances become evident on ECG and Holter monitoring, including polymorphic premature ventricular complexes, bigeminism and trigeminism, couplets, triplets, atrioventricular heart block, atrioventricular nodal reentrant tachycardia, premature atrial complexes, premature ventricular complexes, and ventricular tachycardia.

Figure 3.

Electrocardiogram at age four years showing left axis deviation (left anterior fascicular block)

Echocardiogram reveals, at the onset of cardiomyopathy, reduced function of the left ventricle and dilatation and global hypokinesia without wall hypertrophy. Later, dilatation involves the left atrium and ventricle, subsequently affecting all chambers leading to congestive heart failure.

Radionuclide angiography using MUGA (multi-gated acquisition) scan reveals the deteriorating ventricular function with reduction of the left ventricular ejection fraction (LVEF) followed by reduction of the right ventricle ejection fraction.

Respiratory function tests show a moderate restrictive pattern without clinical symptoms.

Testing Strategy

To confirm/establish the diagnosis in a proband

Clinical findings that should be present to warrant consideration of skeletal muscle biopsy and molecular genetic testing include:

• Delayed motor milestones but normal cognitive development;
• Muscle weakness of limb-girdle distribution, myopathic face, variable degree of ptosis, and relative calf muscle hypertrophy;
• Dilated cardiomyopathy in association with muscle weakness of limb-girdle distribution.

Skeletal muscle biopsy is an integral part of the diagnostic evaluation because of the marked clinical overlap within and between congenital myopathies and congenital muscular dystrophy (CMD). Muscle biopsy sections should be examined for histology, histochemistry, immunohistochemistry, and electron microscopy.

Note: Cardiac muscle biopsy is currently not indicated following the recognition of the disease.

Molecular genetic testing. If clinical findings and skeletal muscle biopsy suggest Salih myopathy, perform molecular genetic testing:

• Perform sequence analysis of select exons (i.e., Mex1-3) first.
• If no pathogenic variants are identified (especially in individuals not of Moroccan or Sudanese origin), is it appropriate to sequence the other Mex exons.
• If only one frameshift variant is found in Mex1-3, deletion/duplication analysis is recommended to detect a possible deletion of Mex1-6 exons.
• If no pathogenic variants are found in Mex1-3, sequence analysis of the entire coding region could be helpful.
• If no pathogenic variants have been identified by sequence analysis, deletion/duplication analysis may useful to detect a pathogenic variant (for example, homozygous deletion of several exons [e.g., Mex3-6]).

Carrier testing for at-risk relatives requires prior identification of the pathogenic allelic variants in the family.

Note: Carriers are heterozygotes for this autosomal recessive disorder and are not at risk of developing the disorder.

Prenatal diagnosis and preimplantation genetic diagnosis (PGD) for at-risk pregnancies require prior identification of the pathogenic variants in the family.

Clinical Description

Salih myopathy is characterized by muscle weakness manifest during the neonatal period or in early infancy, and delayed motor development. Children acquire independent walking between age 20 months and four years. In the first decade of life, global motor performances are stable or tend to improve. During this period skeletal muscle involvement mainly manifests as difficulty in running, climbing stairs, and rising up from the sitting position. Those who survive childhood remain ambulant, with or without support, and maintain normal cognitive function.

Moderate joint and neck contractures and spinal rigidity may start in the first decade but become more obvious in the second decade. Scoliosis develops after age 11 years.

Cardiac dysfunction starts between age five and 16 years, progresses rapidly, and leads to death between ages eight and 20 years. Heart rhythm disturbances are the major cause of sudden death and their frequency and severity suggest primary involvement of the conduction system.

In contrast to individuals with heterozygous pathogenic variants in TTN associated with Udd distal myopathy, the parents of individuals with Salih myopathy are heterozygous carriers of a TTN pathogenic variant and remain asymptomatic with no cardiac or muscle disorder (Figure 4).

Figure 4.

Mid-calf muscle MRI of parents of a proband at age (A) 55 years and (B) 44 years were normal and showed no fatty degeneration of the anterior tibial muscles.

Genotype-Phenotype Correlations

No genotype-phenotype correlations are known.

Nomenclature

Salih myopathy was initially referred to as Salih congenital muscular dystrophy [Salih et al 1998, Subahi 2001]. Subsequently, it was renamed Salih myopathy [Fukuzawa et al 2008, Pernigo et al 2010].

Prevalence

Salih myopathy is thought to be rare. It has been described in consanguineous families of Arab descent originating from Sudan and Morocco. Actual prevalence figures are unknown.

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs of an individual diagnosed with Salih myopathy, the following are recommended:

• Neurologic examination
• Assessment of strength and joint mobility by physical and occupational therapists
• Assessment of cardiac function with particular attention to possible cardiomyopathy and/or arrhythmia, which are often fatal complications
• Comprehensive respiratory evaluation including assessment of respiratory rate and pulmonary function
• Spinal x-rays to evaluate for presence of scoliosis in the second decade
• Clinical genetics consultation

Treatment of Manifestations

Treatment involves prompt management of disease manifestations using a multidisciplinary approach that includes specialists in pediatric neurology, physiotherapy, occupational therapy, orthopedics, cardiology, and pulmonology.

Stretching exercises and physical therapy help prevent contractures and promote mobility. Assistive mechanical devices including orthotics, canes, and walkers can be used as needed.

Attention to education by providing school technical aid is important since cognition is normal. Stimulation and emotional support can improve school performance and the sense of social involvement.

Parents and/or caregivers should be made aware of the symptoms of heart failure, arrhythmia (including presyncope and syncope), and thromboembolic disease, and of the need to urgently seek medical care when any of these symptoms appear.

Training of caregivers in cardiopulmonary resuscitation may be suggested once the symptoms of cardiomyopathy start.

Adequate posture should be maintained when lying prone and sitting. Garchois brace (made of plexidur, a rigid but light and heat-deformable material) is used to reduce the degree of deformity and slow the progression of scoliosis [Wang et al 2010].

Cardiac transplantation should be considered for progressive dilated cardiomyopathy and heart failure refractory to medical therapy.

Prevention of Secondary Complications

Annual influenza vaccine and other respiratory infection-related immunizations are advised.

Lower respiratory tract infections should be treated aggressively when they occur.

Surveillance

Monitor as follows:

• Every six months: cardiac function (by ECG, 24-hour Holter-ECG recording and echocardiography) starting at age five years.
• Yearly: respiratory function, using pulmonary function testing or spirometry.
• As needed: orthopedic complications (foot deformity, joint contractures, and spinal deformity) by clinical examination and x-rays as needed.

Agents/Circumstances to Avoid

Ibuprofen (Brufen^®):

• Give with care in those with evidence of cardiomyopathy. A patient who had reduced LVEF developed edema following its administration [Subahi and Salih, unpublished observation]
• Avoid in those with congestive heart failure.

Evaluation of Relatives at Risk

Early diagnosis of at-risk sibs by clinical examination and/or molecular genetic testing is important in order to monitor motor development and cardiac function so that treatment can be instituted early.

See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.

Pregnancy Management

If a fetus is diagnosed prenatally to have Salih myopathy, special considerations are needed at and following delivery since muscle weakness may manifest during the neonatal period.

Therapies Under Investigation

Search ClinicalTrials.gov for access to information on clinical studies for a wide range of diseases and conditions.

Mode of Inheritance

Salih myopathy is inherited in an autosomal recessive manner.

Risk to Family Members

Parents of a proband

• The parents of an affected child are obligate heterozygotes (i.e., carriers of one mutated allele).
• Heterozygotes (carriers) are asymptomatic. Note: In contrast to individuals with heterozygous pathogenic allelic variants in TTN associated with Udd distal myopathy, the parents of individuals with Salih myopathy are heterozygous carriers of a TTN pathogenic variant and remain asymptomatic with no cardiac or muscle disorder (Figure 4).

Sibs of a proband

• At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
• Once an at-risk sib is known to be unaffected, the risk of his/her being a carrier is 2/3.
• Heterozygotes (carriers) are asymptomatic.

Offspring of a proband

• No individuals with Salih myopathy have reproduced.
• Unless an individual with Salih myopathy has children with an affected individual or a carrier, his/her offspring will be obligate heterozygotes (carriers) for a pathogenic variant in TTN.

Other family members. Each sib of the proband’s parents is at a 50% risk of being a carrier.

Carrier Detection

Carrier testing for at-risk family members is possible if the pathogenic variants in the family have been identified.

Related Genetic Counseling Issues

See Management, Evaluation of Relatives at Risk for information on evaluating at-risk relatives for the purpose of early diagnosis and treatment.

Family planning

• The optimal time for determination of genetic risk, clarification of carrier status, and discussion of the availability of prenatal testing is before pregnancy.
• It is appropriate to offer genetic counseling (including discussion of potential risks to offspring and reproductive options) to young adults who are affected, are carriers, or are at risk of being carriers.

DNA banking is the storage of DNA (typically extracted from white blood cells) for possible future use. Because it is likely that testing methodology and our understanding of genes, allelic variants, and diseases will improve in the future, consideration should be given to banking DNA of affected individuals.

Prenatal Testing and Preimplantation Genetic Diagnosis

Once the pathogenic variants have been identified in an affected family member, prenatal diagnosis for a pregnancy at increased risk and preimplantation genetic diagnosis for Salih myopathy are possible.

Molecular Genetic Pathogenesis

To date, biallelic pathogenic variants reported to cause Salih myopathy are small frameshift deletions in TTN exons Mex1 and Mex3 in consanguineous families of Moroccan and Sudanese origin [Carmignac et al 2007]. Carriers of these frameshift variants (i.e. heterozygotes) are asymptomatic, presumably as a result of nonsense-mediated decay (NMD) of the mutated mRNA. Since homozygotes survive, the NMD cannot be complete. Some titin protein that lacks the last C-terminal domains is produced. Whether the total decrease of titin protein or the loss of C-terminus is more important for the phenotype is not known.

Gene structure. TTN has 363 exons with a coding capacity of 113,414 bp. TTN has a large number of alternative splicing variants, which can result in confusion in exon and nucleotide numbering in the literature [Bang et al 2001, Guo et al 2010]. Transcript variant (N2A) NM_133378.4 is a long transcript with 312 exons that encodes the isoform N2A, the predominant titin isoform in skeletal muscle. For a detailed summary of gene and protein information, see Table A, Gene.

Pathogenic variants. To date, the biallelic variants reported to cause Salih myopathy are small frameshift deletions in TTN exons Mex1 and Mex3 in two consanguineous families of Moroccan and Sudanese origin [Carmignac et al 2007] (Table 2).

Normal gene product. Titin is the biggest single polypeptide in humans, found in numerous isoform size variants. The entire coding region predicts a protein of 38,138 amino acids (4200 kd). Titin is expressed as several different isoforms, caused by alternative splicing, in different skeletal muscles and cardiac muscle [Bang et al 2001, Guo et al 2010].

Titin functions as a template in sarcomere assembly and for maintenance of sarcomere integrity. The titin protein is the third myofilament in the sarcomere along with myosin and actin filaments. Titin spans more than one half the length of a sarcomere in heart and skeletal muscle. Structurally different parts of the protein perform distinct functions (mechanical, developmental, and regulatory) [Carmignac et al 2007]. Titin binds and interacts with a large number of other sarcomeric proteins.

Abnormal gene product. The predicted truncated titins resulting from the frameshift variants in Mex1 and Mex3 are incorporated into ultrastructurally normal sarcomeres in homozygous affected individuals [Carmignac et al 2007]. Therefore, absence of the last five (Mex2-Mex6) exons is compatible with life but causes this severe congenital disorder. Asymptomatic heterozygous carriers of these titin deletions presumably have sufficient full-length titin to result in normal sarcomere function.

Literature Cited

• Bang ML, Centner T, Fornoff F, Geach AJ, Gotthardt M, McNabb M, Witt CC, Labeit D, Gregorio CC, Granzier H, Labeit S. The complete gene sequence of titin, expression of an unusual approximately 700-kDa titin isoform, and its interaction with obscurin identify a novel Z-line to I-band linking system. Circ Res. 2001;89:1065–72. [PubMed: 11717165]
• Boyden SE, Salih MA, Duncan AR, White AJ, Estrella EA, Burgess SL, Seidahmed MZ, Al-Jarallah AS, Alkhalidi HM, Al-Maneea WM, Bennett RR, Alshemmari SH, Kunkel LM, Kang PB. Efficient identification of novel mutations in patients with limb girdle muscular dystrophy. Neurogenetics. 2010;11:449–55. [PMC free article: PMC2944962] [PubMed: 20623375]
• Carmignac V, Salih MAM, Quijano-Roy S, Marchand S, Marchand S, Al Rayess MM, Mukhtar MM, Ja U, Labeit S, Guicheney P, Leturcq F, Gautel M, Fardau M, Campbell KP, Richard I, Estournet B, Ferreiro A. C-terminal titin deletions cause a novel early-onset myopathy with fatal cardiomyopathy. Ann Neurol. 2007;61:340–51. [PubMed: 17444505]
• Ferreiro A, Estournet B, Chateau D, Romero NB, Laroche C, Odent S, Toutain A, Cabello A, Fontan D, dos Santos HG, Haenggeli CA, Bertini E, Urtizberea JA, Guicheney P, Fardeau M. Multi-minicore disease--searching for boundaries: phenotype analysis of 38 cases. Ann Neurol. 2000;48:745–57. [PubMed: 11079538]
• Ferreiro A, Monnier N, Romero NB, Leroy JP, Bonnemann C, Haenggeli CA, Straub V, Voss WD, Nivoche Y, Jungbluth H, Lemainque A, Voit T, Lunardi J, Fardeau M, Guicheney P. A recessive form of central core disease, transiently presenting as multi-minicore disease, is associated with a homozygous mutation in the ryanodine receptor type 1 gene. Ann Neurol. 2002b;51:750–9. [PubMed: 12112081]
• Ferreiro A, Quijano-Roy S, Pichereau C, Moghadaszadeh B, Goemans N, Bonnemann C, Jungbluth H, Straub V, Villanova M, Leroy JP, Romero NB, Martin JJ, Muntoni F, Voit T, Estournet B, Richard P, Fardeau M, Guicheney P. Mutations of the selenoprotein N gene, which is implicated in rigid spine muscular dystrophy, cause the classical phenotype of multiminicore disease: reassessing the nosology of early-onset myopathies. Am J Hum Genet. 2002a;71:739–49. [PMC free article: PMC378532] [PubMed: 12192640]
• Fukuzawa A, Lange S, Holt M, Vichola A, Carmignac V, Ferreiro A, Udd B, Gautel M. Interchains with titin and myomesin target obscuring and obscuring-like 1 to the M-band-implication for hereditary myopathies. J Cell Sci. 2008;121:1841–51. [PubMed: 18477606]
• Guo W, Bharmal SJ, Esbona K, Greaser ML. Titin diversity--alternative splicing gone wild. J Biomed Biotechnol. 2010;2010:753675. [PMC free article: PMC2843904] [PubMed: 20339475]
• Hermans MC, Pinto YM, Merkies IS, de Die-Smulders CE, Crijns HJ, Faber CG. Hereditary muscular dystrophies and the heart. Neuromuscul Disord. 2010;20:479–92. [PubMed: 20627570]
• Jones KJ, Morgan G, Johnston H, Tobias V, Ouvrier RA, Wilkinson I, North KN. The expanding phenotype of laminin alpha2 chain (merosin) abnormalities: case series and review. J Med Genet. 2001;38:649–57. [PMC free article: PMC1734735] [PubMed: 11584042]
• Margeta M, Connolly AM, Winder TL, Pestronk A, Moore SA. Cardiac pathology exceeds skeletal muscle pathology in two cases of limb-girdle muscular dystrophy type 2I. Muscle Nerve. 2009;40:883–9. [PMC free article: PMC2862182] [PubMed: 19705481]
• Nigro V, Aurino S, Piluso G. Limb girdle muscular dystrophies: update on genetic diagnosis and therapeutic approaches. Curr Opin Neurol. 2011;24:429–36. [PubMed: 21825984]
• Pénisson-Besnier I, Hackman P, Suominen T, Sarparanta J, Huovinen S, Richard-Crémieux I, Udd B. Myopathies caused by homozygous titin mutations: LGMD2J and variations of phenotype. J Neurol Neurosurg Psychiatry. 2010;81:1200–2. [PubMed: 20571043]
• Pernigo S, Fukuzawa A, Bertz M, Holt M, Reif M, Steiner RA, Gautel M. Structural insight into M-band assembly and mechanics from the titin-obscurin-like-1 complex. Proc Natl Acad Sci USA. 2010;107:2908–13. [PMC free article: PMC2814874] [PubMed: 20133654]
• Quijano-Roy S, Galan L, Ferreiro A, Cheliout-Héraut F, Gray F, Fardeau M, Barois A, Guicheney P, Romero NB, Estournet B. Severe progressive form of congenital muscular dystrophy with calf pseudohypertrophy, macroglossia and respiratory insufficiency. Neuromuscul Disord. 2002;12:466–75. [PubMed: 12031620]
• Quijano-Roy S, Mbieleu B, Bönnemann CG, Jeannet PY, Colomer J, Clarke NF, Cuisset JM, Roper H, De Meirleir L, D'Amico A, Ben Yaou R, Nascimento A, Barois A, Demay L, Bertini E, Ferreiro A, Sewry CA, Romero NB, Ryan M, Muntoni F, Guicheney P, Richard P, Bonne G, Estournet B. De novo LMNA mutations cause a new form of congenital muscular dystrophy. Ann Neurol. 2008;64:177–86. [PubMed: 18551513]
• Salih MA, Al Rayess M, Cutshall S, Urtizberca JA, Al-Turaiki MH, Ozo CO, Straub V, Akbar M, Abid M, Andeejani A, Campell KP. A novel form of familial congenital muscular dystrophy in two adolescents. Neuropediatrics. 1998;29:289–93. [PubMed: 10029346]
• Salih MAM. Approach to diagnosis and treatment of a child with motor unit disease. In: Elzouki AY, Stapleton FB, Whitley RJ, Oh W, Nazer H, Harfi HA, eds. Textbook of Clinical Pediatrics. 2 ed. New York, NY: Springer-Verlag; 2012a.
• Salih MAM. Hereditary and acquired myopathies. In: Elzouki AY, Stapleton FB, Whitley RJ, Oh W, Nazer H, Harfi HA, eds. Textbook of Clinical Pediatrics, 2 ed. New York, NY: Springer-Verlag; 2012b.
• Salih MAM. Muscular dystrophies and myopathies in Arab populations. In: Teebi AS, ed. Genetic Disorders among Arab Populations. 2 ed. Heidelberg, Germany: Springer-Verlag; 2010:145-79.
• Subahi SA. Distinguishing cardiac features of a novel form of congenital muscular dystrophy (Salih cmd). Pediatr Cardiol. 2001;22:297–301. [PubMed: 11455396]
• Wang CH, Bonnemann CG, Rutkowski A, Sejersen T, Bellini J, Battista V, Florence JM, Schara U, Schuler PM, Wahbi K, Aloysius A, Bash RO, Béroud C, Bertini E, Bushby K, Cohn RD, Connolly AM, Deconinck N, Desguerre I, Eagle M, Estournet-Mathiaud B, Ferreiro A, Fujak A, Goemans N, Iannaccone ST, Jouinot P, Main M, Melacini P, Mueller-Felber W, Muntoni F, Nelson LL, Rahbek J, Quijano-Roy S, Sewry C, Storhaug K, Simonds A, Tseng B, Vajsar J, Vianello A, Zeller R. Consensus statement on standard of care for congenital muscular dystrophies. J Child Neurol. 2010;25:1559–81. [PMC free article: PMC5207780] [PubMed: 21078917]

Acknowledgments

The Authors would like to thank Loida M Sese for secretarial work, and Sayed Taha and Vir Salvador for medical illustration.

Revision History

• 12 January 2012 (me) Review posted live
• 28 October 2011 (mas) Original submission