Adult onset limb-girdle muscular dystrophy — A recessive titinopathy masquerading as myositis

• Rarely, inflammation can be present in genetic myopathies.
• A patient who was firstly diagnosed with polymyositis did not respond to therapy.
• Exome sequencing disclosed compound heterozygous mutations in the titin gene.
• In western blotting, a severe reduction of titin was observed.
• This recessive adult onset case of titinopathy expands the LGMD2J phenotype.

Rarely, inflammation can be present in genetic myopathies, such as dysferlinopathies, facioscapulohumeral muscular dystrophy and GNE-myopathy (hereditary inclusion body myopathy). This may lead to erroneous initial diagnosis and unnecessary therapy which bear serious side effects. We report on an unusual case of mutations in the TTN gene presenting with inflammatory infiltrates in the muscle biopsy. Only after intensive immune-modulating therapies failed, a genetic myopathy was considered. Exome sequencing and search for mutated muscle protein-encoding genes disclosed compound heterozygous mutations in TTN: K26320T and A6135G. The parents carry one each of the mutations. Titinopathy could be considered also in patients presenting with inflammatory infiltrates resistant to therapy.