Fig. 4

a Direct gene sequencing analysis of PMM2 gene revealed the substitution of T for C at position 395 in exon 5, this mutation existed in the patient and his mother (right); another mutation was the absence of TAAGA at position 458_462 in exon 6, this mutation presented in the patient and his father (left). b Cross-species comparison of phosphomannomutase 2 protein sequence showed that the isoleucine (I) residue at amino acid position 132 was conserved from protists to primates (shown by the box), which suggested that mutation in this amino acid position may affect the normal structure and function of phosphomannomutase 2. c With pedigree analysis, we found that the patient’s father was heterozygous for the I153X mutation with normal phosphomannomutase 2 activities and his mother was heterozygous for the I132T mutation with normal phosphomannomutase 2 activities, while our patient (arrow) was a proband in his family and carried two mutations derived from his parents with decreased levels of phosphomannomutase 2 activities. PMM2 phosphomannomutase 2