Spinal Muscular Atrophy with Respiratory Distress Type 1 (SMARD1)
SMARD1 is a rare form of infantile-onset spinal muscular atrophy, characterized by severe early respiratory failure due to diaphragmatic paralysis and progressive muscle weakness. Unlike SMA5q (classic SMA with mutations in SMN1), it primarily affects the distal and respiratory muscles. SMARD1 has an estimated incidence of 1 in 100,000 live births, with an onset typically between 6 weeks and 6 months of age. It does not respond to therapies aimed at increasing SMN expression (unlike classic SMA).
SMARD1, also known as infantile axonal neuropathy with dysautonomia, is caused by biallelic (autosomal recessive) mutations in the IGHMBP2 gene, which encodes a protein involved in RNA maturation. The dysfunction of this gene leads to the degeneration of motor neurons in the spinal cord and peripheral nerve fibers, with particular vulnerability of the phrenic nerves that innervate the diaphragm.
-
Acute or progressive early-onset respiratory failure
-
Distal muscle weakness (lower limbs more severely affected than upper limbs)
-
Pes cavus (high-arched feet) and tendon retractions/contractures
-
Fasciculations, hypotonia, and absence of reflexes (areflexia)
-
Possible autonomic nervous system involvement (arrhythmias, bladder dysfunction)
-
Genetic analysis for IGHMBP2 gene mutations via direct sequencing or Next-Generation Sequencing (NGS) analysis.
-
Electromyography and nerve conduction studies.
-
Respiratory function assessment (diaphragmatic paralysis).
-
Differential diagnosis with other forms of SMA and hereditary neuropathies.
Available therapies
Currently, there are no approved therapies to modify the disease course; management is exclusively multidisciplinary to improve the quality of life:
-
Early mechanical ventilation (invasive or non-invasive)
-
Respiratory and motor physiotherapy
-
Assisted nutrition
-
Regular follow-up (cardiology, respiratory, and nutrition)
Research in progress
Ecco la traduzione tecnica degli attuali sforzi della ricerca sulla SMARD1:
Current Research & Experimental Directions
-
Preclinical studies on gene therapy aimed at restoring the IGHMBP2 gene.
-
Animal models and organoids to investigate the underlying pathogenesis.
-
RNA-corrective molecule approaches.
-
Personalized medicine projects.
The “Centro Dino Ferrari” is an international reference center for this condition. Researchers at the “Dino Ferrari Centre” have developed a preclinical gene therapy protocol for this disease and are working toward its clinical translation. Reagents and methodologies are available for the complete diagnosis of the IGHMBP2 gene, along with the validation of molecular defects using molecular and biochemical techniques on patient tissues and cells.
Reference laboratory
Contacts and informations
Prof.ssa Stefania Corti
stefania.corti@unimi.it
https://pubmed.ncbi.nlm.nih.gov/35086940/