Objective Non-idiopathic CPP is caused by acquired or congenital hypothalamic lesions visible on MRI or is associated with various complex genetic and/or syndromic disorders. This study investigated the different types and prevalence of non-isolated CPP phenotypes. Design and Methods This observational cohort study included all patients identified as having non-idiopathic CPP in the database of a single academic pediatric care center over a period of 11.5 years. Patients were classified on the basis of MRI findings for the CNS as having either hypothalamic lesions or complex syndromic phenotypes without structural lesions of the hypothalamus. Results In total, 63 consecutive children (42 girls and 21 boys) with non-isolated CPP were identified. Diverse diseases were detected, and the hypothalamic lesions visible on MRI (n = 28, 45% of cases) included hamartomas (n = 17; either isolated or with an associated syndromic phenotype), optic gliomas (n = 8; with or without neurofibromatosis type 1), malformations (n = 3) with interhypothalamic adhesions (n = 2; isolated or associated with syndromic CNS midline abnormalities, such as optic nerve hypoplasia, ectopic posterior pituitary) or arachnoid cysts (n = 1). The patients with non-structural hypothalamic lesions (n = 35, 55% of cases) had narcolepsy (n = 9), RASopathies (n = 4), encephalopathy or autism spectrum disorders with or without chromosomal abnormalities (n = 15) and other complex syndromic disorders (n = 7). Conclusion Our findings suggest that a large proportion (55%) of patients with non-isolated probable non-idiopathic CPP may have complex disorders without structural hypothalamic lesions on MRI. Future studies should explore the pathophysiological relevance of the mechanisms underlying CPP in these disorders.
