ESPE Abstracts

Objective: To report the clinical and gene mutation characteristics of a patient with lysine urinary protein intolerance (LPI) characterized by lupus nephritis, lupus encephalitis and extreme short stature, so as to improve understanding of the clinical characteristics of LPI caused by SLC7A7 gene mutation.

Methods: The clinical manifestation, laboratory examination and gene test results of a child with LPI diagnosed and treated in our hospital were analyzed retrospectively, and the relevant literature was reviewed.

Results: A 7-year-old boy with growth retardation, rash, systemic edema and mental abnormalities came to our hospital. He had anorexia of high protein food since childhood, and had growth and mental retardation since 3 year-old. At the age of 6, he was diagnosed as nephrotic syndrome due to multiple rashes, proteinuria, edema of eyelids and limbs. After administration of prednisone, the rash and edema subsided. However, mental symptoms such as indifference, delirium and gibberish began to appear. On physical examination, he weighed 13.7 kg (- 3.3 SD) and 99.8 cm tall (- 5.4 SD). He appeared with round face, slightly wide eye distance, dark skin all over the body, and obvious pigmentation at the extremities and joints. Laboratory examination showed that Hb 104g/l, anti SSA antibody (+), anti nuclear antibody (+), complement C3 and C4 decreased. Blood LDH and blood ammonia increased, serum alanine, citrulline and glutamine increased, uracil, urinary whey acid and urinary 4-hydroxyphenyllactic acid increased. But the child had multiple system involvement and extremely short stature that could not be explained by SLE, Whole exon sequencing showed that it was a double heterozygous mutation of SLC7A7 gene (c.551A>C and c.719C>T). The mutation came from his mother and father respectively, and was diagnosed as LPI complicated with SLE.

Conclusion: The clinical manifestations of LPI are not characteristic. Lupus nephritis and lupus encephalitis are very rare. When there is protein intolerance, growth retardation and multiple system damage, we should be alert to the possibility of LPI. Blood and urine amino acid analysis, blood ammonia and renal tubular function can help the diagnosis. SLC7A7 gene sequencing is the basis for the diagnosis.