Beyond pain: early Hypotonia and growth failure in congenital insensitivity to pain with Anhidrosis

Abstract

Congenital insensitivity to pain with anhidrosis is a rare genetic disorder caused by mutations in the neurotrophic receptor tyrosine kinase 1 gene, characterized by absent pain perception and inability to sweat. Early recognition is essential to prevent severe complications. We report a seven-month-old boy presenting with poor growth, hypotonia, and delayed motor development. Initial metabolic and neuromuscular evaluations, including nerve conduction studies and brain imaging, were normal. His growth remained at the minus three standard deviation centile. By twelve months, additional features emerged, including self-injurious behavior, lack of response to injury, and reduced sweating. A positive family history prompted genetic testing, which confirmed a pathogenic variant in the neurotrophic receptor tyrosine kinase 1 gene. This case highlights that early nonspecific features may precede classical manifestations, emphasizing the importance of clinical vigilance, family history, and early genetic testing to enable timely multidisciplinary management.