Case Report: Optic neuritis as the initial presentation of Orientia tsutsugamushi infection detected by metagenomic next-generation sequencing.

Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi infection, and typically manifested as fever, eschar, lymphadenopathy, rash, and other flu-like signs. Ocular involvement was not uncommon, and mostly occurred at post-fever or recovery stage in scrub typhus cases. We hereby report a case of scrub typhus presenting as unilateral optic neuritis (ON). A 56-year-old man going wild fishing nearly every day complained of a blurred vision and an inferior visual field defect in the right eye two or three days after an insect-bite like shin induration in his left leg. He was diagnosed as ON, and treated with dexamethasone in the local hospital. Unfortunately, his right eye vision progressively deteriorated during steroid therapy. Three days after steroid therapy ceased, he suffered from a high fever and painful subcutaneous masses in the left groin. Peripheral blood test by metagenomic next-generation sequencing (mNGS) was positive for Orientia tsutsugamushi, but negative for other pathogens. The diagnosis was then revised to scrub typhus and ON. His systemic symptoms rapidly disappeared after oral doxycycline and omadacycline therapy. However, his right eye vision continuously deteriorated to hand motion. Further serum tests for aquaporin 4-IgG antibody and myelin oligodendrocyte glycoprotein-IgG antibody were both negative, but for anticardiolipin IgM and beta-2-glycoprotein-I IgM were both positive. The patient's right eye vision gradually improved after doxycycline combined with steroid pulse therapy. Our case indicates that ON in scrub typhus cases may present as a parainfectious inflammation, and that mNGS is a useful and valuable method for early diagnosis of scrub typhus.

Case Report: Severe Optic Neuritis after Multiple Episodes of Malaria in a Traveler to Africa.

Although local transmission of malaria has been eliminated, the disease is frequently imported to China by Chinese travelers returning from Africa. Optic neuritis (ON) is occasionally reported in malarial cases and usually shows good visual recovery and prognosis. Herein, we report severe visual loss with poor recovery due to bilateral ON in a malarial patient who traveled from Nigeria. While he was still in Nigeria, his visual acuity dropped to no light perception in both eyes after the third episode of malaria, which was confirmed by a positive blood smear for malarial parasites. His general condition gradually improved after a 6-day course of artesunate therapy. However, visual acuity in both eyes remained unchanged after artesunate therapy alone, with gradual improvement subsequently shown after pulse steroid therapy. Our case indicates that early antimalarial drugs combined with pulse steroid therapy may be of great importance for good visual recovery in ON cases after malarial infection.