Background: Crisponi/cold-induced sweating syndrome (CS/CISS) is a rare autosomal recessive disorder characterized by severe neonatal manifestations including paroxysmal muscle contractions, tendency for hyperthermia, and feeding and swallowing difficulties with high neonatal mortality. Pathogenic variants in the Cytokine Receptor-Like Factor 1 (CRLF1) gene have been associated with CS/CISS. These variants result in a loss of function of the encoded protein, which disrupts the formation of a functional heterodimer with Cardiotrophin-Like Cytokine Factor 1 (CLCF1). This complex is essential for the development of autonomic and sensory nervous systems, as well as for bone remodeling. We report two patients affected by CS harboring pathogenic variants in the CRLF1 gene. Methods—case reports: The first patient was diagnosed postnatally, presenting with non-epileptic paroxysmal events characterized by opisthotonus and orofacial contractions. He survived beyond infancy, later developing scoliosis and persistent episodes of hyperthermia. In the second patient, a prenatal ultrasound at 20 weeks of gestation revealed bilateral camptodactyly, also referred to as the ‘horn’s sign’, raising early suspicion of CS. The diagnosis was subsequently confirmed both clinically and genetically. After birth, the infant developed severe dysphagia, apnea, and paroxysmal events not associated with epileptiform activity on EEG. Sanger sequencing identified a homozygous c.708_709delinsT frameshift variant in the CRLF1 gene. The patient died at 30 days of age due to respiratory failure. Results and conclusions: With this manuscript, we aim to further delineate the phenotypic spectrum of this rare condition and propose the ‘horn’s sign’ as a targeted prenatal marker for early diagnosis in populations with known founder mutations or familial risk factors.