Bone quality in LAMA2-related muscular dystrophy and SELENON-related congenital myopathy, a one-year prospective natural history study

Fragility fractures are frequently reported in neuromuscular diseases and negatively influence functional prognosis, quality of life and survival. In LAMA2-related muscular dystrophy (LAMA2-MD) and SELENON(SEPN1)-related congenital myopathy (SELENON-RM) cross-sectional and prospective natural history studies on bone quality and fragility long bone fractures (LBFs) are lacking. We therefore aim to systematically assess bone quality and provide recommendations for clinical care. We performed a one-year prospective natural history study in 21 LAMA2-MD and 10 SELENON-RM patients including a standardized fracture history and bone quality assessment through dual energy Xray absorptiometry scan (DEXA-scan) and/or bone health index (BHI). Ninety percent of the LAMA2-MD and SELENON-RM patients showed low bone quality. Eight (38%) LAMA2-MD and five (50%) SELENON-RM patients had a history of fragility LBFs. During the one-year follow-up period, one LAMA2-MD patient (female, 3 years) experienced a fragility LBF of the right humerus. We found no difference in bone mineral density between baseline and one-year follow-up. Based on general international guidelines for osteoporosis, we advise adequate vitamin D and calcium intake, and standardized clinical follow-up through a DEXA-scan or BHI in all LAMA2-MD and SELENON-RM patients. On indication, patients should be referred to the pediatrics or internal medicine for consideration of additional treatments.

Muscle magnetic resonance imaging in patients with LAMA2-related muscular dystrophy

LAMA2-related muscular dystrophy (LAMA2-MD) is classified into congenital muscular dystrophy type 1A (MDC1A) and autosomal recessive limb-girdle muscular dystrophy-23 (LGMDR23). The purpose of this study was to identify the involvement pattern of thigh muscles of LAMA2-MD patients on magnetic resonance imaging. Fourteen MDC1A and 3 LGMDR23 patients were included, with 21 known and 8 novel LAMA2 disease-causing variants. In LAMA2-MD, the gluteus maximus, anterior (quadriceps femoris) and posterior (adductor magnus and biceps femoris) thigh muscles were extensively and severely affected with fatty infiltration, with relatively sparing of the adductor longus. The pattern of muscle involvement was similar between MDC1A and LGMDR23, but more severe in MDC1A, as well as in LAMA2-MD patients without ambulation. The rather peculiar pattern of the adductor magnus and long head of the biceps femoris first and severely affected in the mid-thigh level was found in LGMDR23. Strong correlation between fatty infiltration and age as well as disease duration was observed for the adductor longus in MDC1A. Edema and atrophy selectively involved in some muscles. The pattern of fatty infiltration on thigh muscle MRI of LAMA2-MD could provide important information for the diagnosis, differential diagnosis and assessment of clinical severity.

Whole Exome Sequencing as a Diagnostic Tool for Unidentified Muscular Dystrophy in a Vietnamese Family

Muscular dystrophies are a group of heterogeneous clinical and genetic disorders. Two siblings presented with characteristics like muscular dystrophy, abnormal white matter, and elevated serum creatine kinase level. The high throughput of whole exome sequencing (WES) makes it an efficient tool for obtaining a precise diagnosis without the need for immunohistochemistry. WES was performed in the two siblings and their parents, followed by prioritization of variants and validation by Sanger sequencing. Very rare variants with moderate to high predicted impact in genes associated with neuromuscular disorders were selected. We identified two pathogenic missense variants, c.778C>T (p.H260Y) and c.2987G>A (p.C996Y), in the LAMA2 gene (NM_000426.3), in the homozygous state in two siblings, and in the heterozygous state in their unaffected parents, which were confirmed by Sanger sequencing. Variant c.2987G>A has not been reported previously. These variants may lead to a change in the structure and function of laminin-α2, a member of the family of laminin-211, which is an extracellular matrix protein that functions to stabilize the basement membrane of muscle fibers during contractions. Overall, WES enabled an accurate diagnosis of both patients with LAMA2-related muscular dystrophy and expanded the spectrum of missense variants in LAMA2.