Mental retardation in Duchenne muscular dystrophy: its relation to the maternal carrier state

Global prevalence of intellectual developmental disorder in dystrophinopathies: A systematic review and meta-analysis

AIM

To estimate the global prevalence of intellectual developmental disorder (IDD) and the IDD prevalence-genotype association in Becker muscular dystrophy (BMD) or Duchenne muscular dystrophy (DMD) according to the affected isoforms of the DMD gene: Dp427, Dp140, Dp71.

METHOD

Systematic searches in MEDLINE, Scopus, Web of Science, and the Cochrane Library were conducted from inception of each database to March 2022. Observational studies that determined the prevalence of IDD in the population with BMD or DMD were included. Meta-analyses of IDD prevalence and prevalence ratios of the IDD-genotype association were conducted.

RESULTS

Forty-nine studies were included. The prevalence of IDD in BMD was 8.0% (95% confidence interval 5.0-11.0), and in DMD it was 22.0% (18.0-27.0). Meta-analyses of IDD-genotype association showed a deleterious association between IDD and the number of isoforms affected in DMD, with a prevalence ratio = 0.43 (0.28-0.64) and 0.17 (0.09-0.34) for Dp140⁺ /Dp71⁺ versus Dp140^- /Dp71⁺ and Dp140⁺ /Dp71⁺ versus Dp140^- /Dp71^- comparisons respectively. However, in BMD, there was no association for Dp140⁺ /Dp71⁺ versus Dp140^- /Dp71⁺ .

INTERPRETATION

There is a high prevalence of IDD in BMD and DMD. Moreover, the number of isoforms affected is strongly and negatively associated with the prevalence of IDD in DMD.

Synaptic alterations as a neurodevelopmental trait of Duchenne muscular dystrophy

Dystrophinopaties, e.g., Duchenne muscular dystrophy (DMD), Becker muscular dystrophy and X-linked dilated cardiomyopathy are inherited neuromuscular diseases, characterized by progressive muscular degeneration, which however associate with a significant impact on general system physiology. The more severe is the pathology and its diversified manifestations, the heavier are its effects on organs, systems, and tissues other than muscles (skeletal, cardiac and smooth muscles). All dystrophinopaties are characterized by mutations in a single gene located on the X chromosome encoding dystrophin (Dp427) and its shorter isoforms, but DMD is the most devasting: muscular degenerations manifests within the first 4 years of life, progressively affecting motility and other muscular functions, and leads to a fatal outcome between the 20s and 40s. To date, after years of studies on both DMD patients and animal models of the disease, it has been clearly demonstrated that a significant percentage of DMD patients are also afflicted by cognitive, neurological, and autonomic disorders, of varying degree of severity. The anatomical correlates underlying neural functional damages are established during embryonic development and the early stages of postnatal life, when brain circuits, sensory and motor connections are still maturing. The impact of the absence of Dp427 on the development, differentiation, and consolidation of specific cerebral circuits (hippocampus, cerebellum, prefrontal cortex, amygdala) is significant, and amplified by the frequent lack of one or more of its lower molecular mass isoforms. The most relevant aspect, which characterizes DMD-associated neurological disorders, is based on morpho-functional alterations of selective synaptic connections within the affected brain areas. This pathological feature correlates neurological conditions of DMD to other severe neurological disorders, such as schizophrenia, epilepsy and autistic spectrum disorders, among others. This review discusses the organization and the role of the dystrophin-dystroglycan complex in muscles and neurons, focusing on the neurological aspect of DMD and on the most relevant morphological and functional synaptic alterations, in both central and autonomic nervous systems, described in the pathology and its animal models.

Brain morphology in Duchenne muscular dystrophy: a Golgi study

Intellectual impairment associated with Duchenne muscular dystrophy is well recognized, although no consistent anatomic central nervous system lesions have been reported. The autopsy findings of 13 patients, ages 13-18 years, were reviewed. Intelligence quotients, ascertained in 5 patients, ranged from 46-79. Gross and microscopic examinations of brain and spinal cord revealed no consistent pattern of abnormalities. Neuropathology included neuronal loss and gliosis in spinal gray matter and tegmental brainstem, extensive Purkinje cell loss, mononuclear perivascular cuffing with cortical and subcortical gliosis, and cerebral heterotopia. Quantitative analysis of rapid Golgi impregnations of the visual cortex revealed significantly reduced dendritic length and branching of apical and basal dendrites from pyramidal neurons in 1 patient and less striking attenuation of dendritic arborization in 2 others. The literature suggests that the intellectual deficit in Duchenne muscular dystrophy is nonprogressive and unrelated to age or severity of muscle disease, although performance intelligence quotient may deteriorate with progressive muscle weakness. Golgi analysis suggested that abnormal dendritic development and arborization may underlie intellectual impairment. Although the pathogenesis of the cellular defect is not fully known, the coexistence of central nervous system and muscle pathology raises the possibility of a common molecular mechanism.

Reactions of families to children with Duchenne muscular dystrophy

Twenty-five families were interviewed to examine their adjustments to having a child with Duchenne muscular dystrophy (DMD). Chronic emotional stress experienced by families of DMD children was found to be a significant problem in the overall management of the illness. Based on information obtained from the assessment of families' adaptation to their child's illness, recommendations are made concerning parent education, school placement, facilitation of marital harmony, informing the child about his illness, and sensitivity to the responses of other family members.