Editing Myasthenia gravis (section)

=== Differential diagnoses ===
The muscle weakness that worsens with activity (abnormal [[muscle fatigue]]) in myasthenia gravis<ref name=":0">{{Cite journal |last=Gilhus |first=Nils Erik |date=2021-03-01 |title=Physical training and exercise in myasthenia gravis |url=https://www.sciencedirect.com/science/article/pii/S0960896620306982 |journal=Neuromuscular Disorders |volume=31 |issue=3 |pages=169–173 |doi=10.1016/j.nmd.2020.12.004 |issn=0960-8966 |pmid=33461846 |s2cid=229372884 |hdl-access=free |hdl=11250/2767222}}</ref> is a symptom shared by other neuromuscular diseases. Most of the [[Metabolic myopathy|metabolic myopathies]], such as McArdle disease (GSD-V), have abnormal muscle fatigue rather than fixed muscle weakness.<ref>{{Cite journal |last1=Darras |first1=B. T. |last2=Friedman |first2=N. R. |date=February 2000 |title=Metabolic myopathies: a clinical approach; part I |url=https://pubmed.ncbi.nlm.nih.gov/10738913/ |url-status=live |journal=Pediatric Neurology |volume=22 |issue=2 |pages=87–97 |doi=10.1016/s0887-8994(99)00133-2 |issn=0887-8994 |pmid=10738913 |archive-url=https://web.archive.org/web/20230524221141/https://pubmed.ncbi.nlm.nih.gov/10738913/ |archive-date=24 May 2023 |access-date=24 November 2023}}</ref><ref>{{Cite journal |last=Tobon |first=Alejandro |date=December 2013 |title=Metabolic myopathies |journal=Continuum (Minneapolis, Minn.) |volume=19 |issue=6 Muscle Disease |pages=1571–1597 |doi=10.1212/01.CON.0000440660.41675.06 |issn=1538-6899 |pmc=10563931 |pmid=24305448}}</ref> Also, like myasthenia gravis,<ref name=":0" /> exercise intolerance in [[McArdle disease]] improves with regular physical activity (performed safely using activity adaptations such as getting into [[Second wind#Pathology|second wind]], the "30 for 80 rule," and "six second rule").<ref>{{Cite book |last=Wakelin |first=A. |url=https://www.iamgsd.org/_files/ugd/c951b2_91a5802caa2144d5aedbb0489c1cf543.pdf |title=Living with McArdle Disease |publisher=IamGSD |year=2017 |access-date=24 November 2023 |archive-url=https://web.archive.org/web/20230305215516/https://www.iamgsd.org/_files/ugd/c951b2_91a5802caa2144d5aedbb0489c1cf543.pdf |archive-date=5 March 2023 |url-status=live}}</ref><ref>{{Cite journal |last1=Reason |first1=S. L. |last2=Voermans |first2=N. |last3=Lucia |first3=A. |last4=Vissing |first4=J. |last5=Quinlivan |first5=R. |last6=Bhai |first6=S. |last7=Wakelin |first7=A. |date=July 2023 |title=Development of Continuum of Care for McArdle disease: A practical tool for clinicians and patients |journal=Neuromuscular Disorders |volume=33 |issue=7 |pages=575–579 |doi=10.1016/j.nmd.2023.05.006 |issn=1873-2364 |pmid=37354872 |s2cid=259141690 |doi-access=free}}</ref> A small minority of patients with McArdle disease also have the comorbidity of ptosis (drooping upper eyelid).<ref>{{Cite journal |last1=Scalco |first1=Renata S. |last2=Lucia |first2=Alejandro |last3=Santalla |first3=Alfredo |last4=Martinuzzi |first4=Andrea |last5=Vavla |first5=Marinela |last6=Reni |first6=Gianluigi |last7=Toscano |first7=Antonio |last8=Musumeci |first8=Olimpia |last9=Voermans |first9=Nicol C. |last10=Kouwenberg |first10=Carlyn V. |last11=Laforêt |first11=Pascal |last12=San-Millán |first12=Beatriz |last13=Vieitez |first13=Irene |last14=Siciliano |first14=Gabriele |last15=Kühnle |first15=Enrico |date=2020-11-24 |title=Data from the European registry for patients with McArdle disease and other muscle glycogenoses (EUROMAC) |journal=Orphanet Journal of Rare Diseases |volume=15 |issue=1 |pages=330 |doi=10.1186/s13023-020-01562-x |issn=1750-1172 |pmc=7687836 |pmid=33234167 |doi-access=free}}</ref> Late-onset GSD-II ([[Pompe disease]]) and GSD-XV also have muscle weakness or fatigue with comorbidities of ptosis and ophthalmoplegia; as do many of the [[Mitochondrial myopathy|mitochondrial myopathies]].<ref name=":3">{{Cite journal |last1=Urtizberea |first1=Jon Andoni |last2=Severa |first2=Gianmarco |last3=Malfatti |first3=Edoardo |date=May 2023 |title=Metabolic Myopathies in the Era of Next-Generation Sequencing |journal=Genes |volume=14 |issue=5 |pages=954 |doi=10.3390/genes14050954 |issn=2073-4425 |pmc=10217901 |pmid=37239314 |doi-access=free}}</ref>

Other diseases that involve abnormal muscle fatigue (which may be described as exercise-induced muscle weakness, reversible muscle weakness, or muscle weakness that improves with rest) include: endocrine myopathies (such as [[Hoffmann syndrome|Hoffman syndrome]]), Tubular aggregate myopathy (TAM), [[ischemia]] (such as [[intermittent claudication]], [[popliteal artery entrapment syndrome]], and [[chronic venous insufficiency]]), and poor diet or malabsorption diseases that lead to [[vitamin D deficiency]] (osteomalic myopathy). Although limb-girdle muscular dystrophies (LGMDs) involve fixed muscle weakness, LGMDR8 also involves muscle fatigue;<ref>{{Cite web |title=MUSCULAR DYSTROPHY, LIMB-GIRDLE, AUTOSOMAL RECESSIVE 8; LGMDR8 |url=https://www.omim.org/entry/254110 |url-status=live |archive-url=https://web.archive.org/web/20240531123356/https://www.omim.org/entry/254110 |archive-date=31 May 2024 |access-date=2023-11-24 |website=www.omim.org }}</ref> as do some limb-girdle muscular dystrophy-dystroglycanopathies such as MDDGC3 (a.k.a. LGMDR15 and LGMD2O).<ref name=":3" /><ref>{{Cite web |title=MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (LIMB-GIRDLE), TYPE C, 3; MDDGC3 |url=https://www.omim.org/entry/613157 |url-status=live |archive-url=https://web.archive.org/web/20230609063352/https://omim.org/entry/613157 |archive-date=9 June 2023 |access-date=2023-11-24 |website=www.omim.org }}</ref> Myofibrillar myopathy 10,<ref>{{Cite web |title=MYOFIBRILLAR MYOPATHY 10; MFM10 |url=https://www.omim.org/entry/619040 |url-status=live |archive-url=https://web.archive.org/web/20240421111521/https://omim.org/entry/619040 |archive-date=21 April 2024 |access-date=2023-11-24 |website=www.omim.org }}</ref> dimethylglycine dehydrogenase deficiency,<ref>{{Cite web |title=DIMETHYLGLYCINE DEHYDROGENASE DEFICIENCY; DMGDHD |url=https://www.omim.org/entry/605850 |url-status=live |archive-url=https://web.archive.org/web/20221014230504/https://omim.org/entry/605850 |archive-date=14 October 2022 |access-date=2023-11-24 |website=www.omim.org }}</ref> erythrocyte lactate transporter defect,<ref>{{Cite web |title=ERYTHROCYTE LACTATE TRANSPORTER DEFECT |url=https://www.omim.org/entry/245340 |url-status=live |archive-url=https://web.archive.org/web/20240513063740/https://www.omim.org/entry/245340 |archive-date=13 May 2024 |access-date=2023-11-24 |website=www.omim.org }}</ref> and myopathy with myalgia, increased serum creatine kinase, with or without episodic rhabdomyolysis (MMCKR)<ref>{{Cite web |title=MYOPATHY WITH MYALGIA, INCREASED SERUM CREATINE KINASE, AND WITH OR WITHOUT EPISODIC RHABDOMYOLYSIS; MMCKR |url=https://www.omim.org/entry/620138 |url-status=live |archive-url=https://web.archive.org/web/20240603103141/https://www.omim.org/entry/620138 |archive-date=3 June 2024 |access-date=2023-11-24 |website=www.omim.org }}</ref> also include muscle fatigue.

X-linked episodic muscle weakness (EMWX) includes general muscle weakness, ptosis, and fluctuations in strength. In some individuals, fatiguability was demonstrable, the phenotype having features comparable to congenital myasthenic syndromes and [[Channelopathy|channelopathies]].<ref>{{Cite web |title=EPISODIC MUSCLE WEAKNESS, X-LINKED; EMWX |url=https://www.omim.org/entry/300211 |url-status=live |archive-url=https://web.archive.org/web/20240703204110/https://www.omim.org/entry/300211 |archive-date=3 July 2024 |access-date=2023-11-24 |website=www.omim.org }}</ref>

Signs and symptoms of myasthenia presenting from infancy or childhood may be one of the [[congenital myasthenic syndrome]]s, which can be inherited in either an autosomal dominant or recessive manner. There are currently over two dozen types of congenital myasthenic syndromes.<ref>{{Cite web |title=Phenotypic Series - PS601462, PS610542 - Congenital myasthenic syndromes - OMIM |url=https://www.omim.org/phenotypicSeries/PS610542,PS601462 |url-status=live |archive-url=https://web.archive.org/web/20240703204110/https://www.omim.org/phenotypicSeries/PS610542,PS601462 |archive-date=3 July 2024 |access-date=2023-11-24 |website=www.omim.org}}</ref>

Limb–girdle myasthenia gravis is a distinct condition from myasthenia gravis. It is an adult-onset, autoimmune condition affecting the neuromuscular junction. However, it lacks eye abnormalities and is associated with autoimmune conditions such as systemic lupus erythematosus, Hashimoto's thyroiditis, and thymoma.<ref>{{Cite web |title=159400 - MYASTHENIA, LIMB-GIRDLE, AUTOIMMUNE - OMIM |url=https://www.omim.org/entry/159400 |url-status=live |archive-url=https://web.archive.org/web/20230602162212/https://omim.org/entry/159400 |archive-date=2 June 2023 |access-date=2024-02-29 |website=www.omim.org }}</ref>

[[Lambert–Eaton myasthenic syndrome]] (LEMS) is an autoimmune condition that attacks the neuromuscular junction, either as a paraneoplastic syndrome (typically older patients) or associated with a non-cancerous primary autoimmune condition (typically younger patients). It usually involves lower limb weakness and exercise-induced fatiguability, although the upper limbs and eyes may also be involved. Lambert's sign is the unusual improvement of grip strength that follows after squeezing the hand at maximum intensity for 2–3 seconds.<ref>{{Cite journal |last1=Pascuzzi |first1=Robert M. |last2=Bodkin |first2=Cynthia L. |date=2022 |title=Myasthenia Gravis and Lambert-Eaton Myasthenic Syndrome: New Developments in Diagnosis and Treatment |journal=Neuropsychiatric Disease and Treatment |volume=18 |pages=3001–3022 |doi=10.2147/NDT.S296714 |issn=1176-6328 |pmc=9792103 |pmid=36578903 |doi-access=free}}</ref>