What Are The Causes Of Lesch-Nyhan Syndrome?

Lesch-Nyhan Syndrome: What You Need to Know

Lesch-Nyhan Syndrome (LNS) is a rare genetic disease, especially in males, caused by an enzyme deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT). This leads to an increased uric acid body burden. Due to this, patients with LNS have a mix of neurological deficits, behaviour disturbances, and metabolic abnormalities. Most significant among the behaviour disturbances are self-injury, such as lip biting and head banging, and involuntary movement, such as chorea, dystonia, and ballismus.

To learn more about it, keep on reading!

What is Lesch-Nyhan syndrome?

Lesch-Nyhan Syndrome is an X-linked recessive genetic disorder that primarily affects males. It is defined by overproduction of uric acid—a purine metabolite end product—a condition that leads to its accumulation in blood and tissues. The excess uric acid produced will crystallise and deposit intramuscularly, leading to gout-like arthritis and kidney or bladder stones.

Apart from the metabolic challenges, LNS influences the nervous system and behaviour predominantly. LNS individuals will generally display involuntary and repetitive muscle movements such as

• Muscle stiffness or stiffness (dystonia)
• Sudden jerky, involuntary movement (chorea)
• Flailing movements of arms and legs (ballismus)

Motor impairments typically prevent affected individuals from walking, sitting independently, or doing simple tasks. The majority require the assistance of a wheelchair. One of the most distinguishing features of LNS is compulsive self-harm, particularly once the child’s teeth come in.

What are the symptoms of Lesch-Nyhan syndrome?

The condition manifests early in life, typically before 12 months of age. Symptoms mainly affect motor ability, cognition, and behaviour. Although in some infants, the symptoms may be evident earlier with the presence of orange-coloured uric acid crystals within the nappies, in other instances, the symptoms tend to become apparent around the age of 4 months.

Behavioural Symptoms

Self-mutilation that is uncontrollable is one of the characteristics of LNS and comprises:

• Biting lips, cheeks, or fingers
• Head or limb banging or hitting
• Eye poking
• Sometimes, children also present with aggressive behaviours against others, such as:
• Hitting, pinching, or grabbing others
• Spitting or verbal outbursts

Motor and Movement Difficulties

Children with LNS typically present with features of motor dysfunction, which can include:

• Repeated limb movement (ballismus)
• Muscle stiffness
• Poor coordination of tasks like crawling or feeding
• Speech difficulty (dysarthria)
• Difficulty with swallowing (dysphagia)
• Overactive reflexes (hyperreflexia)
• Involuntary facial movements or twisting actions (choreoathetosis)
• Muscle spasms causing back arching (opisthotonos)

Physical Health Complications

Owing to the elevated concentration of uric acid, patients may develop:

• Kidney stones or bladder stones
• Chronic kidney disease or kidney failure
• Gout attacks
• Megaloblastic anaemia, which is generally associated with vitamin B12 deficiency
• Frequent episodes of vomiting

Cognitive and Learning Challenges

Children with Lesch-Nyhan Syndrome may also face intellectual and developmental challenges like:

• Learning issues
• Shorter attention span
• Poor memory
• Difficulty in problem-solving or planning complex tasks

What Causes Lesch-Nyhan Syndrome?

Lesch-Nyhan syndrome occurs due to a mutation of a single gene, the HPRT1 gene, that encodes for a vital enzyme called HPRT. The enzyme is of essential importance to the body's metabolic process, as it catalyses chemical reactions.

In patients with this condition, the body can't adequately break down purines—natural chemicals in most food and cells. When the purines aren't broken down, they're diverted to uric acid, which is a waste product that needs to be flushed out of the body via the urine.

But in Lesch-Nyhan syndrome, there is an overaccumulation of uric acid in the body (hyperuricemia), creating small crystals or stones called urates. These can accumulate in fingers, toes, joints, and skin and typically result in inflammation and discomfort called gout.

Further, urate crystals are precipitated in the kidneys or bladder and lead to obstructive urinary tract disease as well as intense pain. In more serious cases, this can progress to kidney failure if not managed appropriately.

How is Lesch-Nyhan syndrome treated?

Management of Lesch-Nyhan syndrome is tailored according to each child’s symptoms and the extent of their condition.

Newborns and young infants with this condition may require specialised care, such as feeding therapy and close monitoring of their health. Treatment can involve:

• Medications like allopurinol reduce uric acid levels, but behavioral symptoms require physical restraints (e.g., mittens) and behavioral therapy.
• Nutritional and swallowing therapy, particularly in infants with eating issues.
• Mobility assistance such as wheelchairs to facilitate movement.
• Therapies, including physical and occupational therapy, to aid motor development.
• Protective devices, like mouthguards or splints, to reduce harm from self-injurious behaviours such as biting.
• Surgical treatments, like shockwave therapy or laser lithotripsy, to shatter kidney or bladder stones.

Diagnosis of Lesch-Nyhan syndrome can overwhelm the emotions of the families, given its rarity and the absence of a specific cure. However, with early intervention and regular medical treatment, the quality of life of the patient can be significantly improved. It is advisable to discuss the appropriate treatment options with your health practitioner that can benefit your child's growth and development.

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