An unusual case of dermatomyositis with muscle hypertrophy and neuromyotonia

Texas clinicians report the highly atypical case of a 65-year-old patient initially diagnosed with dermatomyositis on the basis of classic disease criteria:

• the initial picture consisted of a muscle deficit that appeared a few weeks after a rash on the face,
• the work-up revealed hyperCKemia at 4,000 IU/l, positive autoantibodies to Mi2, inflammatory infiltrates and perifascicular atrophy on muscle biopsy,
• the patient also showed signs of peripheral nerve hyperactivity, with involuntary muscle contractions predominating in the upper limbs, and hypertrophy visible to the naked eye,
• EMGTracé rendant compte de l’activité électrique produite par la contraction musculaire, enregistré à l’aide d’une aiguille fine implantée dans le muscle. Il permet de savoir si le problème musculaire est dû à une atteinte des muscles ou à une atteinte des nerfs. abnormalities were also consistent with an additional Isaacs syndrome, but without any biological signature, since anti-potassium channel antibodies, LGI-1 antibodies and CASPR2 antibodies were negative.

According to the authors, this association between two rare pathologies is not fortuitous and could be the result of exacerbated autoimmunity.

An Unusual Presentation of Dermatomyositis With Muscle Hypertrophy. Bailey G, Trivedi JR. Cureus. 2023 Juin.