Clinical and genetic characteristics of type I sialidosis patients in mainland China

Abstract

ObjectiveType I sialidosis (ST‐1) is a rare autosomal recessive inherited disorder. To date, there has been no study on ST‐1 patients in mainland China.MethodsWe reported in detail the cases of five Chinese ST‐1 patients from two centers, and summarized all worldwide cases. Then, we compared the differences between Chinese and foreign patients.ResultsA total of 77 genetically confirmed ST‐1 patients were identified: 12 from mainland China, 23 from Taiwan, 10 from other Asian regions, and 32 from European and American regions. The mean age of onset was 16.0 ± 6.7 years; the most common symptoms were myoclonus seizures (96.0%), followed by ataxia (94.3%), and blurred vision (67.2%). Compared to other groups, the onset age of patients from mainland China was much younger (10.8 ± 2.7 years). The incidence of visual impairment was lower in patients from other Asian regions than in patients from mainland China and Taiwan (28.6% vs. 81.8%–100%). Cherry‐red spots were less frequent in the Taiwanese patients than in patients from other regions (27.3% vs. 55.2%–90.0%). Furthermore, 48 different mutation types were identified. Chinese mainland and Taiwanese patients were more likely to carry the c.544A > G mutation (75% and 100%, respectively) than the patients from other regions (only 0%–10.0%). Approximately 50% of Chinese mainland patients carried the c.239C > T mutation, a much higher proportion than that found in the other populations. In addition, although the brain MRI of most patients was normal, 18F‐FDG‐PET analysis could reveal cerebellar and occipital lobe hypometabolism.InterpretationST‐1 patients in different regions are likely to have different mutation types; environmental factors may influence clinical manifestations. Larger studies enrolling more patients are required.

Sialidosis type 1 without cherry-red spots: a case report and literature review

“… 12 In patients diagnosed in Taiwan and mainland China, the most common types of mutations arec.544A>G. In contrast, the chance of cherry-red spots appearing in type I sialidosis reported in mainland China is notably higher than in Taiwan. 9 In this report, our first patient from the Hainan Free Trade Port caused by a mutation in this gene c.544A>G, and the patient did not show cherry-red spots in the fundus. Given the geographical proximity to Taiwan, we hypothesise that the presence of cherry-red spots may be related to the environment.…”

“…Only three cases were detected with cherry-red spots after over 10 years of follow-up 12. In patients diagnosed in Taiwan and mainland China, the most common types of mutations arec.544A>G. In contrast, the chance of cherry-red spots appearing in type I sialidosis reported in mainland China is notably higher than in Taiwan 9. In this report, our first patient from the Hainan Free Trade Port caused by a mutation in this gene c.544A>G, and the patient did not show cherry-red spots in the fundus.…”

“…However, these cherry-red spots may not be detected in clinical examinations for many years and may disappear in the late stages of the disease. Studies by Kivlin et al suggest that these spots may appear early and disappear later,8 while Qun Wang et al summarise that these spots could disappear as the disease progresses or appear 20 years after onset 9. Given the presence of cherry-red spots in the fundus, type I sialidosis is also known as cherry-red spot myoclonus syndrome 3.…”

“…Typically, researchers diagnose sialic acid disease by detecting neuraminidase activity in cultured fibroblasts or leucocytes. The enzyme activity is unstable and generally serves as a screening tool, but genetic testing is also key to a definitive diagnosis 9. Type 1 sialidosis is a progressively worsening disease without any particularly effective cure.…”

“…Studies by Kivlin et al suggest that these spots may appear early and disappear later, 8 while Qun Wang et al summarise that these spots could disappear as the disease progresses or appear 20 years after onset. 9 Given the presence of cherry-red spots in the fundus, type I sialidosis is also known as cherry-red spot myoclonus syndrome. 3 However, Bou Ghannam AS et al reported a case where no cherry-red spots were observed in the fundus.…”