Abstract:

Objective

To investigate the clinical diagnostic features of a case of Kennedy disease（KD） with serum antibody-negative myasthenia gravis （SNMG）.

Methods

The clinical data of a patient with KD combined with SNMG admitted to the Department of Neurology，Xuzhou Municipal Hospital Affiliated to Xuzhou Medical University on June 25，2024 was retrospectively analyzed.The clinical diagnostic characteristics of KD with SNMG were summarized，and the literature was reviewed.

Results

The patient was male，52 years old，and had intermittent limb weakness for 2 years.The symptoms were chronic，progressive and fluctuating，gradually progressing from the proximal end to the distal end，with mild symptoms in the morning and severe symptoms in the evening，accompanied by muscle spasm at the onset of the disease，and tremor was obvious when the upper limbs were raised horizontally.Physical examination showed mild development of the male breast，perioral muscle atrophy，tongue muscle fibrillation，double palmar thenar muscle atrophy，double upper limb deltoid muscle atrophy，double lower limb slender，bilateral limb muscle strength grade 4，postural tremor when both upper limbs were raised horizontally.Serum creatine kinase increased.Electromyography indicated chronic neurogenic injury，with damage to the anterior horn cells of the spinal cord，involving the muscles of the upper and lower limbs，the rectus abdominis and the trapezius.Neostigmine test was positive.The number of CAG repeats in exon 1 region of androgen receptor gene was abnormally amplified.All 5 myasthenia gravis antibodies were negative.KD combined with SNMG was considered.Treatment with the cholinesterase inhibitor pyridostigmine bromide and coenzyme Q₁₀ resulted in significant remission of the patient′s symptoms.

Conclusion

The early misdiagnosis rate of KD combined with SNMG is very high，and clinicians should pay more attention to muscle fatigue as the first symptom of KD.Gene detection is important for the diagnosis of KD.

Key words: Kennedy disease, Myasthenia gravis, Autoantibodies, Genetic testing