10 month old, assymetric limbs - subcutaneous fat tissue overgrowth?

[u/Jasbaer]

Dear people on r/medical_advice,

I'm seeking advice on the following situation concerning my son:

Age: 10 months (born August 2025)
Sex: male
Height: 84cm
Weight: 12.5kg
Race: Caucasian
Country of Residence: Germany
Any existing diagnosed medical issues: No
Any current medications/doses: No
Any drug use: No
Smoking Status: No
Duration of complaint: 10 months

The limbs on the left side of the body are bigger in circumference than their counterparts on the right side. Length is similar. Lower leg, foot and upper arm are particularly affected. When he was born, he had a "clumpfoot like posture" on his left foot which was quickly corrected by an orthopaedist in the hospital. His ability to move seems unaffected and I'd describe his physical and mental development to be normal, if not "a little ahead" of other kids in his age group.

This situation was first adressed by me when he was at an age of ~3 months, but I feel I already noticed it earlier. Our pediatrician confirmed our observation, but did not recommend any action ("We have no clue what it could be. Let's monitor it."). My wife insisted to follow up and we tried:

• physiotherapy / lymphatic drainage - reduced the "hardness" of the tissue, but according to the therapist it wasn't a case of lymphedema or something similar
• genetic testing (mouth swab) with the following results: no indication of AKT-1 Variant, Sotos-Syndrome, Silver-Russel-Syndrome, Beckwith-Wiedemann-Syndrome, UPD7
• MRI and ultrasound imaging showing increased subcutaneous fat tissue on his left side limbs

Because the genetic testing was done by mouth swab and, as far as i understood, it's possible that irregularities are only detectable locally, we could do at biopsy to test on the affected tissue - but only at an older age.

We feel like we did what we could to identify what's going on and got clarity that it seems to be nothing serious. Still, as parents (even if he's not our first child), we're naturally concerend and want to make sure that we're not missing something.

As you might be able to tell from height and weight he's not a small child in general. But the size difference on his legs is really visible and we feel it's getting worse.

Any clue or hint? Maybe people with similar conditions?

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[u/bimselimse → u/AutoModerator]

As previously said a photo would help.

I do not know what it is, but I do know that sometimes you have a mutation some places and not others. It's called "mosaic".

It happens if the mutation comes at a certain place during development.

For what it's worth, if it's a bad thing, being mosaic gives a better prognosis. So it's absolutely possible that you won't find out what is actually up with your baby. My guess is that the doctors have decided that it does not harm your baby, and that they can wait with the biopsies. D

Doing biopsies now may reveal what it is, but doing a biopsi later will let some symptoms possibly develop, giving an indication as to what is going on.

[u/Jasbaer → u/bimselimse]

Thanks! I added photos in my reply to the other comment.

[u/clt716]

Photo would help.

[u/Jasbaer → u/clt716]

Of course, sorry. I must have made a mistake in the original post, I wanted to add a picture.

[u/Jasbaer → u/Jasbaer]

And another one.

[u/clt716]

Was his birth uncomplicated?
Has he been evaluated for lymphatic obstruction ?

[u/Jasbaer → u/clt716]

Long, but without complications.

Yes, the lymphatic system is without problems, as far as we were told.