Björnstad syndrome

Overview

Björnstad syndrome is a rare inherited disorder characterized by the combination of sensorineural hearing loss and pili torti—a condition in which the hair shafts are twisted and brittle, leading to fragile, sparse hair. First described by Swedish physician Roar Theodor Björnstad in 1965, the syndrome typically presents in infancy or early childhood. It is considered a mitochondrial-related disorder due to its connection with defects in a mitochondrial chaperone protein. The condition affects both males and females and varies in severity from person to person.

Causes

Björnstad syndrome is caused by mutations in the BCS1L gene, which provides instructions for making a protein involved in mitochondrial function—specifically the assembly of complex III in the respiratory chain. These mutations disrupt the normal production of cellular energy and affect tissues with high energy demands, such as hair follicles and auditory nerves. The syndrome follows an autosomal recessive inheritance pattern, meaning an affected individual must inherit two copies of the mutated gene—one from each parent.

Symptoms

The two hallmark features of Björnstad syndrome are:

• Sensorineural hearing loss – typically bilateral and present from birth or early infancy. The severity can range from mild to profound and usually does not worsen significantly over time.

• Pili torti – a hair shaft abnormality where the hair appears twisted under a microscope. This leads to brittle, dry, and sparse scalp hair, often evident in infancy. In some cases, eyebrows and eyelashes may also be affected.

Other symptoms are rare, but some individuals may show signs of mitochondrial dysfunction, such as developmental delays or muscle weakness, although these are not consistent features of the syndrome.

Diagnosis

Diagnosis of Björnstad syndrome is based on clinical features and confirmed by genetic testing. Key diagnostic steps include:

• Physical examination – to identify sparse, brittle hair and signs of hearing loss

• Audiometric testing – to evaluate the type and severity of hearing impairment

• Microscopic hair analysis – demonstrating pili torti under polarized light

• Genetic testing – confirming mutations in the BCS1L gene

• Family history assessment – to determine inheritance patterns

Treatment

There is no cure for Björnstad syndrome, so treatment is supportive and symptom-based. Management includes:

• Hearing support:

  • Hearing aids for mild to moderate loss

  • Cochlear implants in cases of severe or profound hearing loss

  • Speech therapy and educational support for language development

• Hair care – gentle handling and moisturizing products may help reduce breakage, although there is no specific treatment for pili torti

• Genetic counseling – for families and carriers of the condition

• Monitoring – for any potential additional mitochondrial symptoms, though rare

Prognosis

The long-term outlook for individuals with Björnstad syndrome is generally favorable. While hearing loss may affect communication and learning, early intervention with auditory support and therapy can help individuals lead normal, productive lives. Hair abnormalities are cosmetic and do not impact health. Life expectancy is typically normal unless additional, rare mitochondrial complications arise. With proper care and support, most individuals can adapt well to the condition.