MedGen

A disease involving the motor neuron. [from MONDO]

The presence of skeletal muscular atrophy (which is also known as amyotrophy). [from HPO]

Proximal spinal muscular atrophy, i.e., muscular weakness and atrophy related to loss of the motor neurons of the spinal cord and brainstem. [from HPO]

Idiopathic short stature is usually defined as a height below the third percentile for chronological age or minus 2 standard deviations (SD) of national height standards in the absence of specific causative disorders (Rao et al., 1997). For a discussion of genetic heterogeneity of quantitative trait loci for stature, see STQTL1 (606255). [from OMIM]

Spinal muscular atrophy (SMA) is characterized by muscle weakness and atrophy resulting from progressive degeneration and irreversible loss of the anterior horn cells in the spinal cord (i.e., lower motor neurons) and the brain stem nuclei. The onset of weakness ranges from before birth to adulthood. The weakness is symmetric, proximal > distal, and progressive. Before the genetic basis of SMA was understood, it was classified into clinical subtypes based on maximum motor function achieved; however, it is now apparent that the phenotype of SMN1-associated SMA spans a continuum without clear delineation of subtypes. With supportive care only, poor weight gain with growth failure, restrictive lung disease, scoliosis, and joint contractures are common complications; however, newly available targeted treatment options are changing the natural history of this disease. [from GeneReviews]