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Saggy infant syndrome


The Saggy infant syndrome is one of the diseases in which a decrease in muscle tone is observed in newborns or in early childhood. In most cases, muscle strength decreases against the background of a decrease in muscle tone, but this is not always accompanied by a decrease in muscle strength. Muscle tone is controlled by the central nervous system, peripheral nervous system and muscles, and therefore disorders in the work of these organs and systems can lead to a violation or decrease in muscle tone. 

Causes associated with the central nervous system include chromosomal pathology, for example, Down syndrome and Turner syndrome, inborn error of metabolism, for example, aminoacidemia, as well as acute brain injuries, for example, hypoxic-ischemic brain damage and brain development abnormalities. Among the causes associated with the peripheral nervous system are spinal muscular atrophy, motor neuron disease, for example, polio, and peripheral nerve abnormalities, including Charcot-Marie-Tooth disease and congenital myasthenic syndrome. 


Newborns with low muscle tone have a variety of symptoms. After birth, there may be weak crying, and breastfeeding may be difficult due to the weakness of sucking. A decrease in muscle resistance to gravity can cause overstretching of the joints, which manifests itself in such characteristic symptoms as the “frog” pose in the supine position. When the child is lifted horizontally, his limbs and head hang down, and when the child is pulled up, the head falls back. In young children with low muscle tone, delays in the development of motor skills are also often observed. For example, delays in the ability to raise a head and turn it, which are early indicators of motor development. 


First of all, it is important to determine the cause of the decrease in muscle tone, whether it is caused by disorders of the central nervous system or the muscles and peripheral nervous system. The severity of tendon reflexes with concomitant encephalopathy, for example, seizures or changes in the level of consciousness, may indicate that the problem is associated with disorders in the central nervous system. A decrease in muscle mass, a slight muscle tremor, as well as a decrease or complete loss of tendon reflexes may indicate disorders in the functioning of muscles and the peripheral nervous system. In children with low muscle tone, quiet crying, weak breast sucking, rapid breathing and limited chest movement are often observed. To identify the cause, the history of the mother’s pregnancy and the condition of the fetus before and after birth should be analyzed. The anamnesis takes into account the main diseases of the mother, the use of medications during pregnancy, fetal mobility, the level of amniotic fluid, the method of delivery during pelvic presentation and the Apgar score. Diagnostic methods include MRI, chromosomal micromatrix analysis and analysis of metabolic disorders. Genetic research is becoming important, since in most cases the causes of the disease may be genetic in nature. 

Treatment and course of the disease

In a number of cases with the syndrome of a saggy infant its causes can be eliminated. For example, with hypothyroidism, the cause can be eliminated by compensating for thyroid hormone deficiency. In addition, the enzyme deficiency characteristic of Pompe disease can be replenished with injections, and with congenital myasthenia syndrome, the use of acetylcholinesterase inhibitors is an effective treatment method. However, methods for eliminating many other causes of the saggy infant syndrome have not been specifically developed, so conservative treatment is carried out depending on clinical manifestations. 

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