Medical case narrative
A baby whose B12 was "normal" — and wasn't the whole story
What happened
A child with cobalamin C disorder (cblC) — an inherited condition that blocks the body's use of vitamin B12 — presented with developmental and psychiatric-type features while the standard B12 blood test looked reassuring.
What it looked like
A child not developing or behaving as expected, with a "normal B12" result that could easily have ended the search.
What the labs found
The deeper tests told the truth: homocysteine of 256 and methylmalonic acid (MMA) of 246 — both massively elevated, showing that B12 was not working inside his cells even though the headline B12 number looked normal.
What changed
A diagnosis with a name, a mechanism, and a treatment path — found only because someone ordered the functional markers instead of stopping at the first number.
The test that told the story
Methylmalonic acid (MMA) and homocysteine — the functional B12 markers.
Sources: Published case report.