PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
Synonyms: spinal muscular atrophy type 1, SMA type 1, infantile spinal muscular atrophy
Werdnig-Hoffmann disease is a rare form of spinal muscular atrophy (SMA) presenting in infants. It is an autosomal recessive condition characterised by the degeneration of anterior horn cells, leading to profound symmetrical weakness and wasting of voluntary muscle . It is the second most common lethal autosomal recessive disease of white populations after cystic fibrosis.
Werdnig-Hoffmann describes a subset of SMA and is distinguished by:
- The age at presentation (before 6 months).
- Severity (death from respiratory failure, typically by the age of 2).
Patients with other forms of SMA - SMA type 2, or Dubowitz syndrome, and SMA type 3, or Wohlfart-Kugelberg-Welander disease - have later onset of symptoms and a slower progression of muscle weakness and respiratory symptoms.
- Werdnig-Hoffmann disease is the most common cause of genetically determined neonatal death.
- It has an incidence in the order of 1:25,000 live births in the UK.
- It has a carrier frequency of 1 in 60-80 in the UK.
- It is more common in boys despite the autosomal recessive inheritance. This appears to be accounted for by cases of sporadic mutation.
The survival motor neuron 1 (SMN1) gene is missing in 93% of all SMA patients and in 50% of cases there will also be absence of both homologues of the neighbouring gene - neuronal apoptosis inhibitory protein (NAIP).
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- Reduced fetal movements during the last trimester in 30%.
- Floppy baby (60%).
- Prolonged cyanosis.
- Severe weakness.
- Respiratory difficulties.
- Difficulty in sucking and/or swallowing.
- Tongue fasciculations.
- Poor head control.
- Facial weakness.
- Absent reflexes.
- Congenital joint contractures.
- Lack of normal motor movements.
- Amyotrophic lateral sclerosis.
- Congenital myotonic dystrophy.
- Congenital myopathies.
- Congenital and neonatal myasthenia gravis.
- Metabolic disorders.
- Arthrogryposis multiplex congenita.
These may include:
- Serum creatine kinase levels - they are usually normal but may be raised.
- Genetic studies.
- Electromyogram (EMG) - may be difficult to interpret in young infants - may see evidence of denervation and reinnervation with normal conduction velocities.
- Muscle biopsy.
No specific therapy is yet available for the treatment of Werdnig-Hoffmann disease. Treatment is not disease-modifying. Affected children should be under the care of a multidisciplinary team with expertise in the management of type 1 SMA.
- Support for the family throughout the lifetime of the child and beyond. Contact with other affected families can be helpful. Children's hospices can offer friendship and respite for affected families.
- The child may benefit from physiotherapy and respiratory support for the relief of symptoms. How aggressive respiratory management should be is controversial: opinion and practice vary from offering no respiratory support to the use of tracheostomy and long-term invasive ventilation. Others occupy a middle position, suggesting measures such as the use of non-invasive ventilation. The ethical dilemma in deciding what is in the child, the family and society's best interest is great. Families need to be involved in these decisions and helped to understand the long-term implications of ventilation.
- Only motor function is affected in these children. Sensation and intellect are normal, so encouraging physical contact and interaction is important, for the well-being of the child and parents.
Werdnig-Hoffmann disease is an orphan disease. However, molecular genetics offer potential targets for drug therapy and the hope of gene therapy. A clinical trial network is being established.
- Progressive kyphoscoliosis.
- Failure to thrive.
- Dysphagia and feeding difficulties.
- Joint contractures.
- High frequency of pathological fractures and hypercalcaemia.
- Respiratory failure.
The outlook for children with Werdnig-Hoffmann disease is very poor:
- Median survival is seven months and 95% of children with the disease have died by the age of 18 months.
- Prognosticating for individual children is difficult however - several studies have cited individual cases where children have had onset of symptoms before the age of 6 months and not developed respiratory failure for years. The genetic basis of this phenotypic variability is not understood.
- Non-invasive respiratory support and prompt treatment of respiratory complications also appear to prolong survival but not to alter the disease course.
Further reading & references
- Spinal Muscular Atrophy Support UK
- Wang CH, Finkel RS, Bertini ES, et al; Consensus statement for standard of care in spinal muscular atrophy. J Child Neurol. 2007 Aug;22(8):1027-49.
- Spinal Muscular Atrophy, Type 1, SMA1; Online Mendelian Inheritance in Man (OMIM)
- Hardart MK, Truog RD; Spinal muscular atrophy--type I. Arch Dis Child. 2003 Oct;88(10):848-50.
- Tsao B & Stojic AS; Spinal muscular atrophy. emedicine, January 2009
- Bush A, Fraser J, Jardine E, et al; Respiratory management of the infant with type 1 spinal muscular atrophy. Arch Dis Child. 2005 Jul;90(7):709-11.
- Iannaccone ST; Modern management of spinal muscular atrophy. J Child Neurol. 2007 Aug;22(8):974-8.
- Bach JR; The use of mechanical ventilation is appropriate in children with genetically proven spinal muscular atrophy type 1: the motion for. Paediatr Respir Rev. 2008 Mar;9(1):45-50; quiz 50; discussion 55-6. Epub 2008 Feb 1.
- Ryan MM; The use of invasive ventilation is appropriate in children with genetically proven spinal muscular atrophy type 1: the motion against. Paediatr Respir Rev. 2008 Mar;9(1):51-4; discussion 55-6. Epub 2008 Feb 1.
- Oskoui M, Kaufmann P; Spinal muscular atrophy. Neurotherapeutics. 2008 Oct;5(4):499-506.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Chloe Borton
Dr Gurvinder Rull
Dr John Cox