FGFR1-related Hartsfield syndrome comprises two core features: holoprosencephaly (HPE) spectrum disorder and ectrodactyly spectrum disorder. HPE spectrum disorder, resulting from failed or incomplete forebrain division early in gestation, includes alobar, semilobar, or lobar HPE. Other observed midline brain malformations include corpus callosum agenesis, absent septum pellucidum, absent olfactory bulbs and tracts, and vermian hypoplasia. Other findings associated with the HPE spectrum such as craniofacial dysmorphism, neurologic issues (developmental delay, spasticity, seizures, hypothalamic dysfunction), feeding problems, and endocrine issues (hypogonadotropic hypogonadism and central insipidus diabetes) are common. Ectrodactyly spectrum disorders are unilateral or bilateral malformations of the hands and/or feet characterized by a median cleft of hand or foot due to absence of the longitudinal central rays (also called split-hand/foot malformation). The number of digits on the right and left can vary. Polydactyly and syndactyly can also be seen.

The features of frontofacionasal dysplasia include blepharophimosis, lower lid lagophthalmos, primary telecanthus, S-shaped palpebral fissures, facial hypoplasia, eyelid coloboma, widow's peak, cranium bifidum occultum, frontal lipoma, nasal hypoplasia, deformed nostrils, bifid nose, and cleft of lip, premaxilla, palate, and uvula (White et al., 1991). Also see frontonasal dysplasia (136760).