Phenotypic and genotypic features of a pair of Chinese identical twins with congenital insensitivity to pain and anhidrosis: A case report

RATIONALE: Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autosomal recessive genetic disorder characterized by insensitivity to noxious stimulus and the absence of sweating. Fractures and joint destruction are common complications, but detailed studies on mineral and skeletal homeostasis are not available. Mental retardation is often reported, but detailed observations during childhood are lacking. PATIENT CONCERNS: A pair of 46-month-old Chinese identical twin brothers was presented at our hospital. The brothers had the typical manifestations of insensitivity to noxious stimulus, inability to sweat, and recurrent episodes of unexplained fever. Fortunately, they did not present common complications such as self-mutilation, trauma, bruise, and repeated bone fractures. DIAGNOSES: Two novel compound heterozygous variants of NTRK1 (c.632T > A and c.1253_1254delTC) were identified. INTERVENTIONS: The patients were subjected to routine and specialist clinical examinations. Daily care and symptomatic treatment were given. OUTCOME: X-ray films of proband 2 showed a fracture in the first metatarsal. Decreased bone mineral density (BMD) and mild-to-moderate retardation of the Gesell developmental schedules (GDS), especially language and adaptability, were observed. Evaluation results for BMD and GDS in proband 2 were worse than those in his brother. LESSONS: The current findings expand our knowledge about the spectrum of phenotypic and genotypic features of CIPA, which will help facilitate future genotype–phenotype association studies. Daily care by parents promotes favorable outcomes in patients.