Selective Mutism in the Context of Autism and Bilingualism

Juan is a 5-year-old boy who has been followed by a developmental-behavioral pediatrician and pediatric neuropsychologist since being diagnosed with language delay and autism spectrum disorder at age 2 years. He is otherwise healthy and was born at term after a healthy pregnancy. His primary language is Spanish, and he has minimal interactions in English. His first words were at 20 months; they were not functional but rather words related to his interests such as "train." He began using 2 to 3-word phrases shortly after but only to request needs. He began speaking in complete sentences at age 4 years.A neuropsychological evaluation was conducted at age 2 years during which Juan demonstrated repetitive behaviors such as hand-flapping, toe-walking, body rocking, and head banging. He displayed sensory seeking behaviors such as rubbing items on his face and close visual inspection. He did not respond to his name and his use of eye contact was inconsistent. He demonstrated rigidity and difficulty transitioning between activities. He did not engage in social reciprocity, and his facial expressions were limited. Minimal spontaneous language was observed, and expressive language largely consisted of echolalia in both languages. Juan was diagnosed with autism spectrum disorder and applied behavior analysis, speech and language therapy, and occupational therapy were recommended.Developmental-behavioral follow-up over the next 2 years noted improvements in behavior, transitions, and social interactions. He participated in early childhood intervention and early childhood special education with significant advances for speech and language in English and Spanish, demonstrating a large vocabulary. At 4 years, parents noted Juan to have reluctance to speak in English. He stopped speaking in English entirely for 3 weeks, though he continued to speak in Spanish. When he resumed speaking in English, it was only with people he knew well (e.g., parents, teachers, babysitter). In clinic, he did not speak to the English-speaking developmental-behavioral pediatrician but spoke in short sentences to the Spanish-speaking neuropsychologist.A repeat neuropsychological evaluation completed at age 5 years revealed that Juan had stopped speaking in English completely, even among those previously deemed "safe." Results were consistent with average cognitive abilities with a strength in verbal skills. Juan's single-word vocabulary in Spanish was exceptionally high. He did not provide expressive responses in English, but his receptive English vocabulary was high average. He responded to English language with nonverbal gestures or spoken language in Spanish. Parents reported Juan to display increased anxiety accompanied by extreme school refusal, behavioral difficulties, and reluctance to leave the home.Given this information, what are your diagnostic considerations and treatment recommendations?