Interestingly, patient 5 showed tremor and ataxia with weakness and numbness mainly involving the distal limbs, which were consistent with the characteristics of anti‐NF155 or CNTN1 antibody positive cases, but the serum antibody test was negative, indicating the patient may have other unknown antibodies, which led to similar clinical manifestations with other antibody‐positive patients. Here, CNTN1 is linked to cerebellar ataxia.