Abstract
BACKGROUND: Methylmalonic acidemia (MMA) is characterized by non-specific symptoms such as vomiting, and feeding difficulties, along with delayed mental and physical development. However, no case of MMA combined with pulmonary fungal infection has been reported yet. CASE SUMMARY: We report the case of a neonate who presented pulmonary fungal infection along with the non-specific features of MMA. Exome sequencing revealed a c.331C>T variant in exon 3 of MMACHC from the father, and a c.658-c.660delAAG variant in exon 4 from the mother, which confirmed the diagnosis of cblC type MMA combined with hyperhomocysteinemia. CONCLUSION: Invasive fungal infection might occur in some infants with MMA. Therefore, early diagnosis is recommended for unexplained pulmonary infection.