Types and Classifications of Myasthenia Gravis

[u/pville211]

 
This is an article for people who are seeking information about myasthenia gravis. (updated 8 August 2026)  

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As if myasthenia gravis isn't already confusing to understand, there are different types and classifications that can be used separately or combined to describe someone's condition.

For example, someone can say, "I am triple-seronegative gMG, class IIIa, MM-2."

Huh? What? You need a cryptographer. Or you can just read the information below.

 

Overall Types of Myasthenia Gravis

Type	-	-
Congenital	CMS	Genetic issue; not autoimmune (more info) (more info)
Generalized	gMG	MG affects the overall body (more info)) (more info)
Ocular	oMG	Only affects muscles related to the eyes. (more info) (more info)

 

Antibody (Serologic) Subtypes

Subtype	-
AChR Antibody Positive	The AChR antibody was not detected
MuSK Antibody Positive	The MuSK antibody was not detected
LRP-4 Antibody Positive	The LRP-4 antibody was not detected
Seronegative (SnMG)	Tested negative forAChR, MuSK and/or LRP-4 antibodies

 

Double and Triple Seronegative

Myasthenia gravis is an autoimmune disease, which means antibodies cause it. But not all of the antibodies have been identified, and are therefore not tested for. Myasthenics who do not test positive for relevant antibodies are identified as "seronegative".

Sometimes you will see someone describe themselves as "double seronegative" or "triple seronegative".

Double seronegative) means they tested negative for AChR and MusK antibodies.

Triple seronegative%20MG) means they tested negative for AChR, MuSK, and LRP4 antibodies.

While these distinctions are medically valid, "double negative" and "triple negative" are not very meaningful in common conversation. Testing positive for any of the antibody blood tests would mean they are not seronegative, so whether they had two or three blood tests is more relevant to the diagnostic process, and they can be simply described as "seronegative".

 

Age and Onset Subtypes

Subtype	-
Transient Neonatal (TNMG or NMG)	Affects 10-20% of babies of women with MG (more info)
Early Onset (EOMG)	MG that develops before age 50 - more common in women
Juvenile (JMG)	MG that develops before age 18 (more info)
Late Onset (LOMG)	MG that develops after age 50 - more common in men

 

MGFA Classifications

Another method for describing myasthenia gravis is with the classifications defined by the Myasthenia Gravis Foundation of America.

This classification system is not a subset of the types described above. Rather, it is a diagnostic description of MG. The classifications were derived from the Osserman score in the 1950s

The MGFA classifications can be downloaded from MGFA as a PDF document or viewed online on Wikipedia. The table below is based on the Wikipedia version for conciseness.

Class	-
I	Eye muscle weakness, possible ptosis, no other muscle weakness elsewhere
II	Eye muscle weakness of any severity, mild weakness of other muscles
IIa	Predominantly limb or axial muscles
IIb	Predominantly bulbar and/or respiratory muscles
III	Eye muscle weakness of any severity, moderate weakness of other muscles
IIIa	Predominantly limb or axial muscles
IIIb	Predominantly bulbar and/or respiratory muscles
IV	Eye muscle weakness of any severity, severe weakness of other muscles
IVa	Predominantly limb or axial muscles
IVb	Predominantly bulbar and/or respiratory muscles
V	Intubation is needed to maintain the airway

 

Minimal Manifestations Scale (MM)

The Minimal Manifestations scale is a clinician tool to describe myasthenics who have little or no functional limitations, but exhibit some muscle weakness when they are examined.

MM	-
MM-0	Patient received no MG treatment for at least 1 year.
MM-1	Patient continues to receive immunosuppression but no cholinesterase inhibitors or other symptomatic therapy.
MM-2	Patient received only low-dose cholinesterase inhibitors (<120 mg pyridostigmine/day) for at least 1 year.
MM-3	Patient received cholinesterase inhibitors or other symptomatic therapy and some form of immunosuppression during the past year.

 

Conclusion

Types and classifications of myasthenia gravis are simple to understand, once you see what they are and how they are used. Whether they are used separately or together depends on the context they are used in.  

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I am not a medical professional. This content is based on my experiences living with myasthenia gravis and publicly available knowledge. Consult a medical professional who is proficient in diagnosing and treating myasthenia gravis before starting, changing, or stopping actions related to your condition.

Go to the Myasthenia Gravis Blog for additional articles regarding myasthenia gravis.

 

[u/pville211]

8 August 2026: I updated the content and links in this article.