Familial writer's cramp: a clinical clue for inherited coenzyme Q10 deficiency

Abstract

The spectrum of coenzyme Q₁₀ (CoQ₁₀) deficiency syndromes comprises a variety of disorders, including a form of autosomal recessive cerebellar ataxia (ARCA2) caused by mutations in the AarF domain-containing kinase 3 gene (ADCK3). Due to the potential response to CoQ₁₀ supplementation, a timely diagnosis is crucial. Herein, we describe two siblings with a novel homozygous ADCK3 variant and an unusual presentation consisting of isolated writer's cramp with adult-onset. Cerebellar ataxia developed later in the disease course and remained stable during the follow-up. This report highlights that ARCA2 should be considered in the differential diagnosis of familial writer's cramp.

Keywords: Ataxia; Coenzyme Q10; Dystonia; Magnetic resonance spectroscopy; Mitochondrial disease; Ubiquinone.

Fig. 1

Sagittal and axial MRI imaging demonstrating cerebellar atrophy in the index patient (a and b) and patient III-3 (c and d). Writing samples depicting writer’s cramp associated dysgraphia (full sentence and first L-letter series written with dominant hand, second L-letter series drawn with non-dominant hand) in the index patient (e) and patient III-3 (f)

Fig. 2

(a) Pedigree of the family with index patient indicated by an arrow. Roman numbers: generations; Arabic numbers: individuals within each generation; circles: women; squares: men; diagonal line: deceased subjects; black: individuals with ARCA2; asterisk: malignancy. (b) Conservation of the described variant among other species