Diagnosis and genetics of alacrima.

Alacrima, the lack of tears, is a rare clinical finding that has been reported as a feature of multiple genetic disorders and can serve as a diagnostic clue to some rare conditions. Causes of alacrima range from absence/hyposecretion of tears to agenesis or improper development of lacrimal gland ducts and associated structures. There are 13 known heritable disorders featuring varying degrees and causes of alacrima. Some manifest only the congenital absence of tears, while others affect multiple organ systems and may involve severe developmental delay, intellectual disability, and potentially life-threatening autonomic dysregulation. To aid in the diagnosis for patients manifesting alacrima, we review the major causes and the various genetic disorders associated with alacrima and provide a differential template for diagnosis.