While instances of total recovery are observed, the condition is often persistent and lesions can reappear even after treatment. Factors that might affect the clinical course of the condition include: the HPV genotype, the age at onset, the elapsed time between the diagnosis and first treatment in addition to previous medical procedures. Other factors, albeit controversial, such as smoking or the presence of gastroesophageal reflux disease might also play a role in the progression of the disease.The papillomas can travel past the larynx and infect extralaryngeal sites. In more aggressive cases, infection of the lungs can occur with progressive airway obstruction. Although rare (less than 1% of people with laryngeal papillomatosis), transformation from a benign form to a malignant form is also observed. Death can result from these complications (morbidity rate is around 1–2%). Epidemiology
Laryngeal papillomatosis is a rare disease with a bimodal distribution based on age of incidence. The incidence, or number of new cases, of laryngeal papillomatosis cases is at approximately 4.3 cases per 100 000 children and 1.8 cases per 100 000 adults annually. The incidence of laryngeal papillomatosis in children peaks before the age of 5, though the term juvenile papillomatosis refers to all cases occurring before the age of 20. The incidence of adult laryngeal papillomatosis, which has an onset after the age of 20, peaks between the ages of 20 and 40. While there are no gender differences in the incidence of laryngeal papillomatosis in children, adult laryngeal papillomatosis occurs more frequently in males than in females.
Because the tandem repeats have identical sequence to one another, base pairing between two DNA strands can take place at multiple points along the sequence. This may lead to the formation of loop out structures during DNA replication or DNA repair synthesis. This may lead to repeated copying of the repeated sequence, expanding the number of repeats. Additional mechanisms involving hybrid RNA:DNA intermediates have been proposed. Diagnosis
See also
C9orf72
RAN translation

References
External links
Trinucleotide+Repeat+Expansion at the US National Library of Medicine Medical Subject Headings (MeSH)
GeneReviews/NCBI/NIH/UW entry on DRPLA
National Institute of Neurological Disorders and Stroke
Genetics Home Reference