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Título

Anti-aquaporin 4 antibody-related myopathy

RESUMO

Case report: 47-years-old Woman, presented bilateral optic neuritis in the third decade of life associated with longitudinal extensive transverse mielitis. Anti-aquaporin 4 antibody was requested and came back positive. Due to clinical picture and positive anti-aquaporin 4 the diagnosis of neuromyelitis optica spectrum disorder (NMSD) was made. Chronically complained of xerostomia and xeroftalmia and had positive anti-Ro antibody. One year ago, noticed pain in lower limb muscles, being worse in the proximal muscles and associated with important fatigue, aggravating the gait that was already compromised by the demyelinating outbreaks. Creatinephosphokinase and aldose were highly elevated. Lower limbs MRI depicted liposubstitution on the T1 sequencing and edema on STIR sequencing, in the anterior compartment of the thigh bilaterally and in the medial gastrocnemius on the right, an image pattern suggestive of myopathy. Discussion: Aquaporin 4 is the most prevalente aquaporin channel in the central nervous system (CNS). Its function is to provid rapid transport of water, maintaining balance and cellular homeostasis. The detection of anti-aquaporin 4 antibody is an importante hallmark in the diagnosis of NMOSD, a well-characterized disease of the CNS. However, aquaprin 4 is also expressed outside the CNS, as in the striated skeletal muscles, and can cause hyperCknemia, myositis with muscle lesions evidenced in muscle byopsy and MRI. We present a case of a patient with NMOSD, with worseneing fatigue and significant myalgia in the lower limbs, elevation of creatinephosphokinase and alsolase, with myopathic image pattern on MRI of the lower limbs. The condition described is an extra-CNS manifestation of anti-aquaporin 4 positive NMOSD and should be screened for in cases of myalgia, worsening of fatigue and gait without evidence of a new demyelinating outbreak. Final comments: The association of anti-aquaporin 4 antibody with NMOSD is well stablished. Currently recognized, but less explored in clinical practice, is its association with myopathy. HyperCKnemia associated with anti-aquaporin 4 antibody should be considered a sign of muscular manifestation of NMOSD. Through this case report we hope to increase knowledge and interest about muscle involvement in anti-aquaporin 4 positive NMOSD.

Palavras Chave

Neuromyelitis optica spectrum disorder, anti-aquaporin 4, myopathy