Dolichocephaly, Arachnodactyly, Diplopia, and Distal Myopathy - Novel Phenotype of MICU1 Variant c.553C>T

Pathogenic variants in mitochondrial calcium uptake 1 (MICU1) manifest phenotypically heterogeneously but most frequently in the brain and skeletal muscle. Dolichocephaly, arachnodactyly, diplopia, and distal myopathy have not been reported in carriers of a pathogenic MICU1 variant. The patient is a 23-year-old female with consanguineous parents (first cousins) who was a carrier of the homozygous MICU1 variant c.553C>T, phenotypically presenting with developmental delay, intellectual disability, ataxia, dysmorphia (dolichocephaly, arachnodactyly, clinodactyly, hypertelorism, wide nasal bridge), myopathy (ptosis, double vision, strabismus, distal limb weakness, diffuse wasting, hypotonia), hyperextensible joints and hyperkyphosis. Features not previously described were dolichocephaly, arachnodactyly, broad nasal bridge, double vision, and distal myopathy. She was treated with physical therapy, speech therapy, and occupational therapy and received escitalopram and mirtazapine for concomitant depression, anxiety disorder, and insomnia. The presented case shows that the phenotypic heterogeneity of pathogenic MICU1 variants is even greater than previously assumed. Treatment of MICU1-related phenotypes is symptomatic, but these patients benefit from physical therapy, behavioral therapy, speech therapy, and antidepressant treatment.