Patients With Extreme Early Onset Juvenile Huntington Disease Can Have Delaysin Diagnosis: A Case Report and Literature Review

摘要

Huntington disease (HD) is caused by a pathologic cytosine-adenine-guanine (CAG)trinucleotide repeat expansion in the HTT gene. Typical adult-onsetdisease occurs with a minimum of 40 repeats. With more than 60 CAG repeats, patients canhave juvenile-onset disease (jHD), with symptom onset by the age of 20 years. We report acase of a boy with extreme early onset, paternally inherited jHD, with symptom onsetbetween 18 and 24 months. He was found to have 250 to 350 CAG repeats, one of the largestrepeat expansions published to date. At initial presentation, he had an ataxic gait,truncal titubation, and speech delay. Magnetic resonance imaging showed cerebellaratrophy. Over time, he continued to regress and became nonverbal, wheelchair-bound,gastrostomy-tube dependent, and increasingly rigid. His young age at presentation and theethical concerns regarding HD testing in minors delayed his diagnosis.