Case Presentation: A 10-month-old infant who had
fever,
vomiting, and
diarrhea for 2 days was referred to our hospital for the following abnormalities in blood tests: white blood cell count, 48,200/μL;
hemoglobin, 9.0 g/dL; and platelet count, 135,000/μL. Bone marrow examination showed a nucleated cell count of 396,000/mm3 and blast cell count of 5.0%, as well as decreased mature granulocyte count and slightly
myeloperoxidase stain-negative blasts but no monoclonal cell proliferation on May-Giemsa staining. Colony assay showed the proliferation of spontaneous colony and high sensitivity to
granulocyte-macrophage colony-stimulating factor. Genetic analysis of peripheral blood mononuclear cells showed that the patient was positive for
neuroblastoma RAS (NRAS) mutation. The patient was ultimately diagnosed with JMML. Approximately 170 days after his first
hematopoietic stem cell transplantation (HSCT), the patient's JMML relapsed. Shortly after the recurrence,
nausea,
vomiting,
hyperventilation, and decreased vitality were observed, followed by a decrease in the level of consciousness. The patient's
ammonia level was 472 μmol/L. A test for seven different genetic mutations for the UCD showed the presence of c. 119G>A (
amino acid change p. Arg40His). As such, late-onset OTCD was added to his diagnosis. Administration of
sodium phenylacetate,
l-arginine hydrochloride, and
carnitine was continued following the diagnosis of OTCD, after which
hyperammonemia was not observed. Regarding JMML relapse, HSCT was performed on day 405 after the first
transplantation.
Conclusion:
Hyperammonemia should be considered a differential diagnosis when unexplained and non-specific symptoms occur during the treatment of
hematologic malignancies. Patients should be tested for UCD as a cause of
hyperammonemia, and treatment for
hyperammonemia should be continued until the cause is identified. The patient shows normal developmental progress, has an intact neurological status, and has not experienced another
hyperammonemia attack. His JMML has remained in remission for over 3 years.