A Pediatric Case of Neurodevelopmental Delay with a Familial H4C11 Variant: Clinical Course and Diagnostic Challenges

Background: Tessadori-Bicknell-van Haaften syndrome (OMIM #619759) is a rare autosomal dominant neurodevelopmental disorder associated with heterozygous variants in genes encoding histone H4 proteins. The condition is characterized by global developmental delay, craniofacial dysmorphism, hypotrophy, intellectual disability, and ophthalmologic anomalies. More than 30 individuals with variants in histone H4 genes have been reported to date, reflecting the genetic heterogeneity of this emerging disorder. According to OMIM, the association between the H4C11 gene and Tessadori-Bicknell-van Haaften syndrome 2 is currently considered provisional. Methods: We report the case of a 5-year-old female presenting with expressive language delay, social interaction difficulties, and craniofacial features including microcephaly, exophthalmos, and periorbital fullness ("puffy eyes"). Family history revealed two sisters with borderline intellectual functioning who have not undergone genetic testing. The patient's father carried the same heterozygous H4C11 variant (c.97C > T), while maternal testing was negative. Results: Neuropsychological evaluation revealed borderline intellectual functioning (IQ 73 at first assessment, 85 at follow-up) with persistent expressive language impairment. Ophthalmologic examination confirmed congenital exophthalmos and hypermetropic astigmatism. Laboratory investigations showed low ferritin and mildly elevated TSH levels, which may have contributed to the observed growth delay. At follow-up, the patient showed an increase in IQ score (73 to 85); however, test-retest variability cannot be excluded. Conclusions: This case highlights the importance of careful clinical assessment and cautious interpretation of genetic findings in children with neurodevelopmental delay. Familial segregation of a variant of uncertain significance (VUS), in the absence of functional evidence, should be interpreted conservatively and integrated with detailed phenotypic evaluation to guide clinical management and follow-up.