FAHN, or Fatty Acid Hydroxylase-associated Neurodegeneration, is an autosomal recessive disorder caused by a mutation in the FA2H gene.
At present, only a few families have been identified with this rare form of NBIA.
Onset usually occurs in childhood featuring leg dystonia, weakness and falling. Affected individuals also experience optic atrophy, profound cerebellar atrophy and white matter changes in the brain, in addition to high brain iron.
Clinical Diagnosis of FAHN
T2-weighted MRI views of the brain with findings showing hypointensity of the globus pallidus and possibly variable unilateral or bilateral symmetric white matter hyperintensity.
Bone marrow biopsy, although not necessary for diagnosis, may demonstrate accumulation of granular histiocytes.
The diagnosis of FAHN may be suspected in individuals with the onset of features in the first or second-decade such as, spasticity, ataxia, dystonia, optic atrophy, eye movement abnormalities early in the disease course and progressive intellectual impairment and seizures later in the disease course.
Spastic paraplegia or quadriplegia and pyramidal tract signs, dysarthria (difficulty pronouncing words), and dysphagia (difficulty swallowing) are other features.
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Treatment is aimed primarily at the dystonia, which can be debilitating. Therapies used with varying success include the oral medications baclofen, anticholinergics, tizanidine, and dantrolene; focal injection of botulinum toxin; intrathecal baclofen; and deep brain stimulation.
Attention should be given to swallowing to prevent aspiration and diet with regular measurement of height and weight in children to assure adequate nutrition with gastrostomy tube placement as needed.
Assessment of ambulation and speech and communication needs, and ophthalmologic examination also recommended.
Please see the link on this page for more detailed clinical information on FAHN at Gene Reviews, which was used as a source for some of the above information. Gene Reviews is primarily for the use of genetics professionals so the terminology and information may be difficult to understand for the general public.
Gene Reviews Authors: Michael C Kruer, MD, Allison Gregory, MS CGC, and Susan J Hayflick, MD.
Please visit the NBIA Disorders Association website, which was used as a primary source for the above information.
To establish the extent of disease in an individual diagnosed with FAHN, the following evaluations may be useful:
Neurologic examination for dystonia, ataxia, and spasticity, including formal evaluation of ambulation, speech, and feeding
Ophthalmologic assessment for evidence of optic atrophy or eye movement abnormalities
Screening developmental assessment, with referral for more formal testing if delay is indicated
Assessment for physical therapy, occupational therapy, and/or speech therapy and appropriate assistive devices