Objective: To explore the clinical manifestations

biochemical characteristics

treatment and prognosis of secondary methylmalonic acidemia (S-MMA) induced by vitamin B12 deficiency. Methods: Clinical manifestations

laboratory examinations

therapeutic effects

maternal pregnancy and biochemical characteristics of 11 children diagnosed with secondary S-MMA induced by vitamin B12 deficiency (S-MMA group) admitted into Henan Children’s Hospital from Jun. 2016 to Jun. 2022 were reviewed. Matching by age and gender at a 1 ∶ 3 ratio

contemporaneous cases diagnosed with cblC-type MMA (C-MMA group) and 10 cases of vitamin B12 deficiency without MMA (non-MMA group) were enrolled. SPSS 20. 0 was used to compare the clinical data of three groups. Results: The main clinical manifestations in three groups of children were anemia

vomiting and developmental delay. Magnetic resonance imaging (MRI) of children in both S-MMA and C-MMA groups showed delayed myelination. In the S-MMA group

the serum vitamin B12 levels increased after treatment compared with before treatment

while mean corpuscular volume (MCV)

homocysteine

acrylic carnitine (C3)

C3/ acetylcarnitine (C3/ C2) ratio

and urinary methylmalonic acid levels decreased

with statistically significant differences (P < 0. 05). The prognosis for S-MMA children was generally good

with very few (9%) showing mild intellectual impairment and motor delay due to delayed diagnosis and treatment. A comparison between S-MMA group and C-MMA group regarding serum vitamin B12 levels

MCV

total homocysteine

C3

C3/ C2 levels

and urinary methylmalonic acid levels before treatment showed statistically significant differences (P<0. 05). Conclusion: Vitamin B12 deficiency during pregnancy can cause S-MMA in infants

and special biochemical indicators can facilitate the early identification of S-MMA.