Spinal musular atrophies are a group of genetic disorders distinguished by progressive degeneration of anterior horn cells in the spinal cord. Proximal weakness of the extremities that may require use of assistive devices and minimal respiratory difficulties appearing between 18 months and 30 years of age are hallmarks of spinal muscular atrophy type 3, also known as Kugelberg-Welander disease.
Spinal muscular atrophies (SMAs) are neurodegenerative disorders caused by mutations in the survival motor neuron 1 (SMN1) gene. Progressive destruction of neurons located in the anterior horn of the spinal cord develops as a result of homozygous deletion of specific segments (exon 7) on SMN1 through autosomal recessive patterns of inheritance . SMAs are estimated to occur in 1 every 10,000 births and type 3 (known as Kugelberg-Welander disease) comprises about 30% of all cases  . The onset of symptoms ranges between 18 months - 30 years of age, and further classification divides type 3 into type 3a (onset between 18 months and 3 years) and 3b (onset between 3-30 years) . Progressive weakness of proximal limbs, more commonly involving the legs than arms, is a typical finding that may be severe enough to require use of a wheelchair or walking aids . Respiratory muscle weakness, which predisposes the majority of patients suffering from type 1 or type 2 to nocturnal hypoventilation, recurrent infections and respiratory failure, as well as swallowing difficulties and scoliosis, are usually absent in type 3 individual, and life expectancy is rarely shortened by complications of the disease   . Additional signs of SMA type 3 are joint pain and preserved cognitive skills . Initial diagnostic workup should comprise serum creatine kinase (CK) levels, electromyography (EMG) and nerve conduction studies, while confirmation can be obtained by using molecular and genetic tests that will detect homozygous deletion of SMN1  . Treatment focuses on symptomatic measures, mainly to provide support when walking or experiencing symptoms of weakness, while more severe measures (insertion of feeding tubes or assisted ventilation) are rarely necessary, and are reserved for more severe forms of SMA (types 1 and 2)   .