Myasthenia gravis, muscular dystrophy, tetany, gout, osteoporosis, arthritis: how do I stop mixing up the cause of each?
Farhan ShaikhDropper Sample
30 Sept 2026 · 1 min read
Disorders at the end of the locomotion chapter are 6 lines in NCERT but they steal marks from me every single test, because the options are all written to sound alike. I've been using my cheap 40-page notebook for this chapter (can't waste pages) and my one-page summary looks like this:
- Myasthenia gravis: something wrong with muscle, weakness, paralysis
- Muscular dystrophy: muscles degenerate, genetic maybe?
- Tetany: spasms, I think due to ... something with calcium
- Arthritis: joint inflammation
- Osteoporosis: bones weak, age, oestrogen
- Gout: uric acid, joints
The trouble is the cause part. In a recent test the question was "autoimmune disorder affecting the neuromuscular junction" and I went for muscular dystrophy. Another one asked "which of these is caused by decreased Ca²⁺ in body fluid" and I had no idea whether it was tetany or osteoporosis.
Can someone give me the one-line cause for each in a way that I won't confuse again? Also, is rheumatoid arthritis different from the NCERT "arthritis" and do I need to know that for NEET? And why is osteoporosis linked to oestrogen, if it's a bone disease?
Thanks in advance, this is the last thing before I move to the next chapter.
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[+][–]Tanvi Deshmukh12thSample· 19d ago
One page, two tables, done!! 🙌
Muscular disorders
Disease Cause / key word Myasthenia gravis autoimmune, affects the neuromuscular junction, fatigue, weakening and paralysis of skeletal muscle Muscular dystrophy genetic, progressive degeneration of skeletal muscle Tetany rapid spasms (wild contractions) due to low Ca²⁺ in body fluid Skeletal disorders
Disease Cause / key word Arthritis inflammation of joints Osteoporosis age-related, decreased bone mass, more fractures; decreased oestrogen is a common cause Gout uric acid crystals accumulate in joints, causing inflammation So your test answers: autoimmune + NMJ = myasthenia gravis, low Ca²⁺ = tetany.
[+][–]Farhan ShaikhDropperSample· 19d agoAuthor
This is perfect, I'm copying both tables into my notebook tonight. Thank you.
[+][–]Riya Singh12thSample· 19d ago
Tetany always confused me too, because calcium helps muscles contract, so I thought tetany = "too much Ca²⁺ = too much contraction". I like having a logical reason so I remembered it like that. I think it's the reverse for osteoporosis, where Ca²⁺ is low in the bones. Is this right?
[+][–]Zoya Khan12thSample· 19d ago
Riya, gentle correction since this is exactly the trap in the options: tetany is from low Ca²⁺ in the body fluid (blood), not high. It sounds backwards, but the logic is that normal levels of Ca²⁺ in the fluid around nerves and muscles keep them from firing too easily, and when the level falls, they become over-excitable and fire spontaneously, giving rapid spasms. And osteoporosis isn't "low calcium in blood", it's decreased bone mass (the bone tissue itself is reduced), so the fracture risk goes up.
[+][–]Farhan ShaikhDropperSample· 19d agoAuthor
Makes sense with the "over-excitable" line, Zoya. Tetany = Tight muscles from low calcium. Locked in 🔒
[+][–]Siddharth RaoDropperSample· 19d ago
The difference between the two muscle ones, in one phrase: myasthenia gravis is a communication problem, muscular dystrophy is a structural problem. In MG the immune system makes antibodies against the receptors for acetylcholine on the muscle side of the neuromuscular junction, so the nerve signal can't properly pass, and the muscle tires out quickly with weakness and paralysis. The muscle itself is OK. In muscular dystrophy the muscle fibres themselves progressively degenerate due to a genetic defect (Duchenne type is X-linked recessive, a gene for the protein dystrophin, so it mostly affects boys).
If the question uses the word "autoimmune", it's MG. If it says "genetic" or "progressive degeneration", it's MD.
[+][–]Lakshmi TripathiDropperSample· 19d ago
For osteoporosis and oestrogen: oestrogen helps maintain bone mass (it slows the breakdown of bone), so when its level falls, as it does in women after menopause, bone loss speeds up. That's why NCERT says decreased oestrogen is a common cause. In the arthritis family, there are several types: osteoarthritis (cartilage wear and tear), rheumatoid arthritis (an autoimmune disease of joints), gout (uric acid crystals). For NEET the NCERT one-liner "inflammation of joints" is enough, but rheumatoid being autoimmune is useful to know for the one question that asks it.
[+][–]Rahul DubeyDropperSample· 19d ago
Cross-chapter link that I use for gout. Uric acid comes from the breakdown of purines (the nitrogen bases A and G in nucleic acids). In birds and reptiles uric acid is the normal waste, in humans it's a minor product, and when too much is in the blood it crystallises in joints. If you did the excretion chapter you already know uric acid is the least soluble of the nitrogenous wastes, so of course it crystallises. 😄 That's why a "uric acid in joints" = gout, and don't confuse it with renal calculi (stones in the kidney, usually oxalates).
