• Patients with HGPRT deficiency are normal at birth.
• One of the first signs of the disease may be the observation of orange crystals in the diapers, or crystalluria with obstruction of the urinary tract.
• Other uncommon forms of presentation include renal failure or acidosis with repeated vomiting. Psychomotor delay, when present, becomes evident within 3 to 6 months.
• A delay in the acquisition of sitting and head support with hypotonia and athetoid movements may lead to neurological consultation. Self-mutilation, in the form of lip biting or finger chewing, can appear as soon as teeth are present.
• Eventually, as uric acid builds up in tissues, symptoms of spasticity, seizures, nephrolithiasis and self mutilation develop.

• Severe, progressive disability if likely.
• Spasticity
• Dystonia
• Choreoathetosis
• Ophisthotonus
• Nephrolithiasis
• Urinary tract infection
• Gouty arthritis
• Skin and soft tissue infections
• Hip dysplasia and subluxation
• Pneumonia
• Scoliosis
• Fractures
• Atlanto-axial joint subluxation^[1]

The prognosis for individuals with LNS is poor. Death is usually due to renal failure in the first or second decade of life.