PHARC - a rare syndrome

What is PHARC syndrome?

PHARC is a very rare syndrome caused by a mutation in the ABHD12 gene. PHARC involves combined visual and hearing impairment/deafblindness, polyneuropathy and cellular ataxia.

The severity of hearing loss, vision loss, polyneuropathy and ataxia varies from person to person. There are individual differences in when in life the conditions occur and how quickly the condition progresses and deteriorates.

The name PHARC is an abbreviation of the English terms for the conditions involved in the syndrome: Polyneuropathy, Hearing loss, Ataxia, Retinitis pigmentosa and Cataract.

Eikholt's course offerings and services apply to everyone with combined visual and hearing impairment/deafblindness, which includes everyone with PHARC who has impaired vision and hearing.

Heredity in PHARC

PHARC is inherited in an autosomal recessive manner and is caused by a mutation in the ABHD12 gene. This means that the person must inherit a mutated gene from each parent to get PHARC. Most people with PHARC have parents who are healthy carriers and do not have PHARC themselves.

Occurrence

PHARC is a very rare syndrome. In the research literature in 2024, only 58 cases of PHARC were described worldwide. One possible reason why this number is low is because not everyone who has PHARC has necessarily participated in research. In Norway, it is estimated that 1 in 36,000 people have PHARC. Because PHARC is hereditary, the syndrome occurs more often in some families, and in some parts of the country. An equal number of women and men have PHARC.

Polyneuropathy

Demyelinating polyneuropathy is one of the main features of PHARC. Nerves in the hands, feet, arms and legs gradually deteriorate, leading to numbness, tingling, pain and muscle weakness. There is great variation in when polyneuropathy occurs for people with PHARC. The most common time for polyneuropathy to occur is in the early 20s, but there is great variation, from early childhood to the 50s. For some, polyneuropathy is the first sign of the syndrome, while others have had vision and hearing loss for many years before polyneuropathy is recognised. The rate at which the nerves deteriorate varies from person to person.

Hearing loss

People with PHARC typically have moderate to severe sensorineural hearing loss in both ears. Some are deaf. The hearing loss can be congenital, occurring in childhood or adolescence. There are also reported cases where the hearing loss was discovered in adulthood. The rate at which hearing deteriorates varies.

If your hearing loss warrants it, hearing aids work well for people with PHARC. Research also shows that people with PHARC benefit from cochlear implant (CI) if the hearing loss indicates this.

Cerebellar ataxia

Cerebellar ataxia is a disease of the cerebellum that can lead to unsteadiness when walking, tremors and difficulties with motor skills and precise movements. Some people may also experience difficulty speaking due to ataxia. Cerebellar ataxia is the PHARC symptom that varies the most between people, both in terms of time of onset and severity. The variation ranges from no signs of cerebellar ataxia, to minor balance problems, all the way to severely reduced fine and gross motor skills.

Retinitis Pigmentosa (RP)

The eye disease Retinitis Pigmentosa is a retinal dystrophy that affects the rods in the retina. RP can lead to night blindness and a narrowed field of vision, and most people experience "tunnel vision". Many experience challenges with glare. As vision loss progresses and becomes severe, visual acuity can also be reduced. There is great variation in when vision loss is recognised, but for people with PHARC, RP is usually discovered in their 20s and 30s. The rate at which vision deteriorates varies, but most people retain some vision well into adulthood.

Cataract (cataract)

Cataract is a condition where the lens of the eye becomes cloudy. This leads to cloudy and blurred vision. Cataracts are a relatively common condition, but people with PHARC and the eye disease Retinitis Pigmentosa often develop cataracts earlier in life than is normal. Some people with PHARC have congenital cataracts. Cataracts can usually be operated on.

PHARC is a spectrum

PHARC manifests itself very differently from person to person. While there are some commonalities, there are also many differences. Usually, the first symptoms appear in childhood or adolescence and progress slowly. There is a big difference in the order in which the symptoms appear. For some, polyneuropathy is the first symptom, while others have only a hearing impairment in the beginning. Some develop vision loss late in life, while others develop vision loss in childhood. Not everyone with PHARC has all five conditions. There is also great variation in how quickly the five conditions progress and deteriorate.

Assessment and differential diagnostics

PHARC is a relatively new diagnosis that was described in the research literature for the first time in 2009 by Norwegian researchers at Haukeland University Hospital.

Because there is great variation in the timing and severity of symptoms, it can be difficult to distinguish PHARC from other diseases and syndromes. In the past, PHARC was often misdiagnosed as atypical Usher syndromeCharcot-Marie-Tooth disease or Refsum's disease.

Today, PHARC can be diagnosed on the basis of genetic testing. When people undergo genetic testing for hearing impairment, visual impairment, neuropathy or ataxia, they will be tested for PHARC.

Treatment and organisation

There is no cure for PHARC. However, the different conditions can be remedied in different ways. Hearing aids or cochlear implants can help with hearing loss. Vision loss can be partially managed with different coping strategies, assistive devices and training. Exercise and physiotherapy can help maintain physical function.

Because PHARC is a syndrome that affects so many different parts of the body, many different professionals are involved in assessment, diagnosis, treatment and rehabilitation. There will be a need for interdisciplinary co-operation in treatment, rehabilitation and training.

Eikholt's experience with PHARC

Eikholt has experience of rehabilitation and training for people with PHARC, and regularly provides services to people with this syndrome. This section summarises some of Eikholt's experiences with people with PHARC.

When vision becomes so impaired that visual reading and writing become difficult, Braille is a poor alternative for people with PHARC due to polyneuropathy. We have good experience that writing with dictation and reading aloud, as well as voice control of mobile phones and other devices, works.

Many people rely on their hearing for communication. When vision loss and polyneuropathy have become severe, Eikholt's experience is that it is difficult to use visual or tactile sign language. These people are therefore dependent on good hearing aids or cochlear implants. Auxiliary hearing aids may be needed to understand speech. In cases of severe polyneuropathy and cerebellar ataxia, it can be difficult to operate small aids such as hearing aids. Polyneuropathy does not necessarily affect the ability to perceive pressure and movement on the back or torso, and people with PHARC may benefit from haptic communication.

In orientation and mobility, unsteadiness and reduced balance are a challenge. Information about and training in the use of interpreter/companion and various aids for orientation and mobility can therefore be relevant to communicate and test.

The article is written 24.03.2025

Sources

Patricia A. Hartz. ABHYDROLASE DOMAIN-CONTAINING PROTEIN 12, LYSOPHOSPHOLIPASE; ABHD12. Onim. Retrieved 24.03.25

Hereditary Ataxia, Also known as hereditary ataxia. ORPHA code: 183518 Hereditary ataxia. Frambu. Retrieved 24.03.25

The genetics portal. Helse Bergen, Department of Medical Genetics. Retrieved 24.03.25

Harutyunyan, L., Callaerts, P. & Vermeer, S. (2024). PHARC syndrome: an overview. Orphanet J Rare Dis, 19(1), 416. https://doi.org/10.1186/s13023-024-03418-0. Retrieved 24.03.2025

Other useful resources

Ragnhild Thomsen Thornam. Statped. The hunt for a rare disease. Published on Research.no. Retrieved 24.03.2025

Statped. Read and watch a video about PHARC here: PHARC | www.statped.no. Retrieved 24.03.25

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