Review Question - QID 107002

The 4-year-old boy is experiencing symptoms of Friedrich's ataxia (FA), which is an autosomal recessive inherited disease. Von Gierke's disease, a glycogen storage disease, is similarly inherited in an autosomal recessive manner.

FA is an autosomal recessive disease caused by an expansion of the trinucleotide GAA on chromosome 9. This expansion leads to an impairment of mitochondrial function which results in cerebellar and spinal cord degeneration. The expansion occurs in the gene frataxin on chromosome 9, which is essential for mitochondrial iron regulation. Typical symptoms are staggering gait, frequent falling, and some patients are wheelchair bound within the first decade of life. On physical exam, the following is noted: nystagmus, dysarthria, decreased vibratory and proprioceptive senses, muscle weakness, absent DTRs, pes cavus (Illustration A), hammer toes (Illustration B), and kyphoscoliosis. These patients typically die in adolescence most commonly due to cardiac arrhythmias, a consequence of hypertrophic cardiomyopathy.

Bidchandani and Delatycki further review FA stating that the mean age of onset is between 10-15 years of age, but typically before 25 years of age. Individuals are usually afflicted with other complications such that 66% have cardiomyopathy and 30% have diabetes mellitus. About 25% of individuals will have an "atypical presentation with later onset or retained tendon reflexes.

Bidchandani and Delatycki discuss the management of FA which involves treating each of the symptoms. For mobility, they recommend walking aids and wheelchairs. Pharmacological treatment is needed for spasticity, the cardiac problems, diabetes mellitus, and bladder dysfunction. They recommend that the individual be assessed at least once a year for their overall condition.

Illustration A demonstrates pes cavus which is a high arch. Illustration B demonstrates a hammer toe which involves the proximal interphalangeal joint and causes the toe to be bent in the shape of a hammer. This is a common in FA patients.

Incorrect answers:
Answer 1: Osteogenesis imperfecta is an autosomal dominant disease.
Answer 3: Menke's disease is an X-linked recessive disease.
Answer 4: Fragile X syndrome is an X-linked dominant disease.
Answer 5: Leber hereditary optic neuropathy is maternal mitochondrial inherited disease.