# Symptoms and phases of spinal muscular atrophy
Spinal muscular atrophy (SMA) progresses in phases that depend heavily on the type of disease. The severity and speed at which symptoms develop differ considerably from person to person. This page describes how symptoms typically manifest and how that affects life.
Type 1 SMA (most severe form, also known as Werdnig-Hoffmann)
**When it starts**
Symptoms usually appear in the first months of life, often before the sixth month. Parents notice that their baby is weaker than expected, moves less, or has difficulty with certain activities.
**Symptoms in this phase: **
- Severe muscle weakness especially in the legs and lower back, but also in the arms
- Difficulty rolling over, sitting, or lifting the head
- Weak sucking reflex and feeding difficulties
- Reduced movement of arms and legs (often described as "floppy" or "limp")
- Tremor (shaking) in the hands, especially when the baby tries to grasp something
- Breathing problems, because the respiratory muscles also become weaker
- Coughing with difficulty swallowing saliva or food properly
**What this means in daily life:**
Babies with type 1 SMA require intensive care. Parents must feed carefully, as the risk of aspiration is high. Many children need help with breathing, sometimes through ventilation. The development of motor skills — such as sitting or walking independently — does not reach normal milestones.
**Survival and course:**
Without treatment, most children with type 1 SMA die before the second year of life, often from respiratory problems. With modern supportive care and new medicines (such as nusinersen or risdiplam), however, the course has changed considerably. Recent data show that many children who are treated early live longer and achieve better motor function — but individual outcomes depend heavily on the timing and intensity of treatment, and how well the body responds to it.
Type 2 SMA (intermediate form)
**When it starts**
Symptoms usually appear between six months and two years of age. The child reaches certain milestones (such as rolling or sitting), but skips others or reaches them much later than usual.
**Symptoms in this phase: **
- Progressive muscle weakness especially in the legs, then also in the arms
- Difficulty sitting upright; many children need help to remain in a sitting position
- Inability to walk independently; some children never learn this
- Loss of movement: a child who could stand may not be able to later
- Difficulty with fine motor skills (reaching, grasping, holding)
- Scoliosis (sideways curvature of the spine), which can worsen over the years
- Contractures: muscles and tendons shrink, causing certain joints to become stiffer
- In some: breathing problems that worsen with infections
- Liver enlargement (hepatomegaly) can occur, especially in earlier stages
**What this means in daily life:**
Children with type 2 SMA often need special aids: orthoses (braces) for legs, walker, wheelchair. School and social participation are possible, but require adjustments. Care and support from parents or caregivers is substantial. Many children need help with personal care and mobility.
**Course and life expectancy:**
Life expectancy for type 2 is highly variable. Some children reach adulthood, others experience more serious complications earlier. Supportive care (ventilation if needed, physiotherapy) and early treatment with medicines have considerably improved the course in recent years. Recent research (2026) shows that treatment with risdiplam can produce motor improvements, but the effects vary greatly from person to person.
Type 3 SMA (milder form)
**When it starts**
Symptoms appear after two years of age, often only later in childhood or even not until puberty. The course is much slower than in type 1 and 2.
**Symptoms in this phase: **
- Progressive muscle weakness in legs and hips, sometimes also in arms
- Difficulty climbing, climbing stairs or walking on uneven ground
- Fatigue faster than in healthy peers of the same age
- Falls, which become more frequent as weakness increases
- Scoliosis, which can be slowly progressive
- Later loss of walking ability (this does not occur in all patients with type 3)
- Limited energy supply: long walks become difficult
**What this means in daily life:**
Many children and young people with type 3 can attend school for a long time, play sports and do normal activities, albeit with limitations. As they get older, they may need to use mobility aids (walking stick, orthosis, eventually possibly wheelchair), but this happens gradually. Work and social participation are very possible for many.
**Course and life expectancy:**
Life expectancy in type 3 is usually normal or close to normal. The progression of muscle weakness is highly individual: some retain their ability to walk throughout their lives, others lose it gradually. Recent research suggests that early detection and treatment with risdiplam can slow progression, although the effects are less dramatic than in type 1 and 2.
Type 4 SMA (adult form)
**When it starts**
Symptoms appear from adulthood onwards, usually after the age of 18, sometimes much later (thirty, forty years or older).
**Symptoms in this phase: **
- Gradual muscle weakness in legs, especially in hips and upper legs
- Increasing fatigue during normal activities
- Progressive loss of muscle strength
- Stability is problematic; falls are more frequent
- Contractures of feet and hands may occur
- Scoliosis may develop
- In general, breathing remains normal much longer than in earlier types
**What this means in daily life:**
The impact varies greatly from person to person and at the time of onset. Someone who develops symptoms at the age of thirty can remain relatively independent for decades. Later, problems with mobility arise, work may require adjustments, and social activities may become limited. Progression is usually slow.
**Course and life expectancy:**
Life expectancy is usually not severely affected, although there are exceptions. The course can be very slowly progressive, sometimes over decades. Treatment with risdiplam is also being investigated for adults, but data are still limited.
---
Changes that can occur across all stages
Regardless of type, certain problems can occur:
**Skeletal problems:**
Scoliosis (sideways curvature of the spine) is very common and can worsen, especially during growth periods. Osteoporosis (weakening of bone tissue) can develop due to restricted movement. This can lead to fractures from relatively minor trauma.
**Nutritional problems:**
Weakness of swallowing and chewing muscles can occur, especially in more severe types. This leads to risk of choking, malnutrition, or need for feeding tube.
**Sleep and breathing problems:**
Breathing muscles become weaker, which especially causes problems at night. Sleep can be disturbed, causing fatigue and concentration problems. In more severe forms, regular ventilation is needed.
**Infections:**
Because coughing is difficult (muscles around the lungs are weak), the risk of pneumonia is greater, especially with colds or flu.
---
When to contact your doctor
Make sure you have regular contact with your treatment team (neurology, physiotherapy, possibly pulmonologist). Report newly occurring complaints, accelerated weakness, difficulties with eating or drinking, or changes in breathing. In case of sudden shortness of breath, severe pain, fever with cough or other emergency symptoms: contact emergency services immediately.
---
_This information never replaces a doctor's judgment. Always discuss your situation with your own healthcare provider._