Most individuals present with developmental delay or growth failure.
Neurological features
- Developmental delay – gross motor skills more commonly affected
- Intellectual disability – mild to severe
- Leigh syndrome-like lesions
- White matter abnormalities
Growth parameters
- Short stature
- Acquired microcephaly
Facial dysmorphism (subtle and variable)
- Long face with a narrow jaw
- Deep set eyes
- Broad nasal tip
- Thin upper lip
- Dental crowding
- High palate
Musculoskeletal abnormalities
- Hypotonia
- Hyporeflexia/areflexia
- Hyperreflexia
- Weakness
- High arches
- Gait abnormalities
- Sensorimotor peripheral neuropathy
Visual and hearing abnormalities
- Hearing loss, progressive, in some cases severe requiring cochlear implants or hearing aids
- Pigmentary retinopathy
Endocrine abnormalities
- Precocious or delayed puberty
- Hypothyroidism
- Growth hormone deficiency
Other less frequently reported features
- Autistic behavior
- Constipation
- Contractures and reduced range of motion
- Feeding difficulties
- Hammertoes
- Movement abnormalities
- Pectus abnormalities
- Scoliosis
- Seizures
- Spasticity
- Strabismus