Dados do Trabalho

Título

Fukutin-related limb-girdle dystrophy presenting as pseudometabolic myopathy.

RESUMO

Case Report
A 35-years-old woman, born from non-consanguineous parents with a Japanese ancestry, presented with an episode of myalgia, dark colored urine, high CK levels after volleyball training at age 15- years-old. During this episode, CK level was 15.450 U/L. She had a spontaneously recovery. She then developed progressive exercise intolerance, mild proximal weakness, and CK levels remained four times upper limit value. Electrodiagnostic studies suggested a myopathic process with normal repetitive stimulation. A muscle biopsy of biceps brachii revealed a mild myopathic pattern with mitochondrial and glycogen accumulation, suggesting a metabolic myopathy.
On a recent visit, physical examination showed MRC 4 in proximal muscles, axial weakness, and winged scapula. Cervical weakness was also noted. She was unable to get up from lying in the examination table. Neuromuscular ultrasound indicated mild hyper echogenicity (Heckmatt 2) in brachialis and vastus intermedius, and moderate hyper echogenicity (Heckmatt 3) in hip adductors and rectus abdominal muscle. Diaphragmatic muscle involvement was also demonstrated. No tongue involvement was seen.
A next generation panel for neuromuscular genes revealed compound heterozygous pathogenic variants in the Fukutin gene (FKTN). DNA segregation confirm the recessive pattern.
Discussion
FKTN biallelic mutations usually present as a congenital myopathy, mainly in Japan and is considered quite rare in other populations. Presentation of limb-girdle manifesting during late childhood is even rarer. Only one case of FKTN related congenital muscular dystrophy was reported in a Japanese patient living in Brazil. In a recent national limb-girdle muscle dystrophy cohort, this gene was not included. As muscle panels are becoming more widespread and accessible, FKTN could be an answer of previous undiagnosed muscle dystrophy in people with a Japanese ancestry.
Conclusions
Brazil has the larger Japanese community outside Japan, therefore FKTN-related myopathies should be considered not only when facing a congenital myopathy or a limb-girdle phenotype, but also when a pseudometabolic myopathy is present. More studies are needed to identify real frequencies of this rare disorder in our country.