Is deltoid muscle biopsy useful in isolated camptocormia? A prospective study

Background and purpose: Camptocormia is a marked anterior curvature of the thoracolumbar spine that may be caused by parkinsonism, amyotrophic lateral sclerosis (ALS), myasthenia gravis (MG) and muscle disease. The interest of a systematic muscle biopsy has not been evaluated until now. In our study, the aim was to prospectively evaluate the proportion of patients with isolated camptocormia without ALS, MG and parkinsonism who have an underlying myopathy. Methods: Twenty consecutive patients (75% female, mean age 70 years) with isolated camptocormia were enrolled in a single centre in this 5-year prospective study. ALS, MG and parkinsonism had been excluded in all cases. A left deltoid muscle biopsy was performed in all patients and processed with standard techniques for histology and immunohistochemistry. Additional biochemical and genetic studies were performed when pathological analysis was consistent with myopathy. Results: A myopathy was identified in seven patients (35%). Three patients presented with mitochondrial myopathy, including two patients harbouring a heterozygous POLG gene pathogenic variant and one patient with a heterozygous RRM2B gene pathogenic variant. Two patients presented with an inflammatory myopathy, including one with anti-PM/Scl antibodies. One patient presented with facioscapulohumeral muscular dystrophy and one patient with an MYH7 gene-related myofibrillar myopathy. No obvious myopathy was found in the 13 remaining cases. Discussion: In this prospective study, an underlying myopathy was found in 35% of patients with isolated camptocormia. These results suggest that a muscle biopsy should be systematically performed in patients with isolated camptocormia when ALS, MG and parkinsonism have been excluded.