Stretch marks are a type of scar which commonly develops when a woman goes through pregnancy, causing the skin to stretch in a short time. This abrupt change will cause the collagen and elastin supporting our skin to rupture, causing the stretch marks.[1]
Excluding the 2 causes that you have mentioned, the other causes of stretch marks include:
- Sudden growth spurt or physiological stretch marks. This usually occurs in adolescents.
- Excessive application of topical steroids causing the skin to thin out.
- Excess corticosteroids in the body either due to intake of oral steroids / repeated steroid injections or an adrenal tumor producing it.
References:
Stretch marks: Why they appear and how to get rid of them | American Academy of Dermatology. Aad.org. https://www.aad.org/public/skin-hair-nails/skin-care/stretch-marks. Published 2019. Accessed September 10, 2019.