Importance of Skin Changes in the Differential Diagnosis of Congenital Muscular Dystrophies

Abstract

Megaconial congenital muscular dystrophy (OMIM 602541) is characterized with early-onset hypotonia, muscle wasting, proximal weakness, cardiomyopathy, mildly elevated serum creatine kinase (CK) levels, and mild-to-moderate intellectual disability. We report two siblings in a consanguineous family admitted for psychomotor delay. Physical examination revealed proximal muscle weakness, contractures in the knee of elder sibling, diffuse mild generalized muscle atrophy, and dry skin with ichthyosis together with multiple nummular eczema in both siblings. Serum CK values were elevated up to 500 U/L. For genetic work-up, we performed whole exome sequencing (WES) after Nimblegen enrichment on the Illumina platform. The WES revealed a novel homozygous missense mutation in the Choline Kinase-Beta (CHKB) gene c.1031G>A (p.R344Q) in exon 9. Ichthyosis-like skin changes with intense pruritus and nummular eczema may lead to clinical diagnosis in cases with megaconial congenital muscular dystrophy.

Figure 1

(a) Dry skin with ichthyosis in the younger sibling at the age of 3 years. (b) Dry skin with nummular eczema in the elder sibling at the age of 8 years. (c) Sanger confirmation of the mutation. Both affected siblings are homozygous and both parents are heterozygous carriers for R344Q mutation. (d) The conservation of the homozygous missense mutation within the vertebrates (http://www.ebi.ac.uk/Tools/msa/clustalw2/).