We present a boy with choline kinase beta mutations with relatively mild clinical manifestations, including proximal weakness, learning difficulties and elevated creatine kinase. Investigations included muscle magnetic resonance imaging (MRI) with T1 axial sequences through thigh and calves, and needle muscle biopsy of the left vastus lateralis muscle.
MRI showed involvement mainly of the quadriceps femoris, sartorius, and adductor magnus, with selective sparing of the gracilis, hamstrings, and adductor longus and brevis. Muscle biopsy revealed chronic dystrophic features. Oxidative stains demonstrated enlarged mitochondria accentuated peripherally or present diffusely in a few fibres giving a coarsely stippled appearance. A homozygous C.722A>G (p.Asn241Ser) mutation was detected in exon 6 of the CHKB gene.
This selective pattern of skeletal muscle involvement might be helpful for identifying other patients with this condition, even in the absence of diagnostic muscle pathology.