Currently, many molecular-targeted agents are used for treatment of various hematological malignancies. Especially, all-trans retinoic acid for acute promyelocytic leukemia, and tyrosine kinase inhibitors for chronic myeloid leukemia (CML) play important roles as curative therapeutic agents, leading to a shift in treatment paradigm. Although the role of molecular-targeted agents in "acute myeloid leukemia (AML) " other than acute promyelocytic leukemia is currently limited, FLT3 inhibitors show efficacy in its relapsed/refractory cases, and venetoclax is used in unfit patients, in combination with azacitidine. The combined use of tyrosine kinase inhibitors and conventional cytotoxic anticancer agents improves treatment outcomes in patients with Philadelphia chromosome-positive acute lymphoblastic leukemia. Also, a novel anti-CD22 antibody is currently available for treatment of patients with acute lymphoblastic leukemia. Treatment strategy of multiple myeloma has been extensively improved by the development of molecular-targeted agents, including immunomodulatory drugs (IMiDs), proteasome inhibitors, and anti-CD38 antibody. In B-cell lymphoma treatment, "rituximab", an anti-CD20 antibody agent, plays significant role as a single agent or in combination with cytotoxic anticancer agents. "Bruton's tyrosine kinase inhibitors" are also currently available for this role. Continuous progress in molecular targeted therapy is requisite for further improvement in clinical outcome of hematological malignancies.

We present a case of a 2-year-old girl with severe Guillain-Barré syndrome (GBS), which is difficult to diagnose early. At day X, she had a fever of 39.0°C, which persisted for 3 days. As soon as the fever resolved, a rash appeared on her trunk and face. She was diagnosed with exanthem subitum. At day X+6, she could not stand and sit alone gradually. At day X+8, she was admitted to our hospital. Physical examination showed nuchal rigidity, extraocular muscle paralysis, lower limb muscle weakness, and tendon reflex weakness. Examination of cerebrospinal fluid revealed an increase in cell number, and nerve root enhancement of the cauda equina was detected on magnetic resonance imaging (MRI) myelography. There was no delay in conduction velocity in the lower limb peripheral nerve conduction examination, but F waves disappeared to 0%. We administered steroid pulse therapy and immunoglobulin therapy (1 g/kg) after considering acute flaccid paralysis. However, at day X+10, she suffered from respiratory failure due to aspiration pneumonia. Pediatric intensive care unit (PICU) management had been administered for 10 days. After an improvement in the respiratory condition, albuminocytologic dissociation was detected in the reexamination of cerebrospinal fluid, and a marked conduction block was detected in the nerve conduction reexamination of the upper and lower limbs. She was diagnosed with GBS, and immunoglobulin therapy (400 mg/kg/day, 3 consecutive days) was added. Rehabilitation was also introduced, and the paralysis of the lower limbs showed gradual improvement. She was able to stand and walk and was discharged at day X+47. Diagnosis of GBS may be delayed due to a lack of significant findings in cerebrospinal fluid and peripheral nerve conduction velocity examinations in the early stage of the disease. However, F wave and MRI myelography may be useful examinations for early diagnosis. In cases of rapidly progressing muscle weakness and respiratory failure, it is important to administer medical treatment with suspicion of GBS.

GNAO1-related disorder is a rare neurodevelopmental disorder associated with epilepsy, developmental delay, and involuntary movements. We encountered a patient with this condition through a research project of the Initiative on Rare and Undiagnosed Diseases (IRUD). The patient was 11 months old at the initial visit and exhibited developmental delay and hypotonia. He had been routinely examined but showed no abnormalities on brain magnetic resonance imaging (MRI), cerebrospinal fluid examination and neurophysiological tests. Truncal hypotonia gradually became evident, but he developed at a moderate pace and walked short distances. At the age of 4 years and 11 months, he received an electroencephalogram and spinal MRI, but no significant results were obtained. At this point, he could walk about 5 meters without support, eat without dysphagia, and understand easy instructions. At the age of 5 years and 4 months, he entered the IRUD with written informed consent from his parents. Chromosomal microarray testing showed no abnormalities, but whole exome sequencing revealed a known variant (NM_020988.3 (GNAO1):c.626G>A [p.Arg209His]) with de novo symptoms. GNAO1 is a causative gene of intractable epilepsy; however, epilepsy is not the most significant factor in some cases. Rather, developmental delay, hypotonia, and involuntary movements are the main clinical features. As there was no contrary evidence, we diagnosed this patient as having a GNAO1-related disorder. Therefore, we confirmed the usefulness of whole exome sequencing in undiagnosed pediatric cases.