Donohue syndrome

Donohue syndrome (also known as leprechaunism) is an extremely rare and severe genetic disorder. Leprechaunism derives its name from the hallmark elvish features (small stature, bulging eyes, thick lips, and upturned nostrils) exhibited by the affected individuals. The disease is caused by a mutation in the INSR gene, which contains the genetic information for the formation of insulin receptors. As a result, affected individuals have either a decreased number of insulin receptors, or insulin receptor with greatly impaired functionality. The lack and impairment of insulin receptor functionality leads to an inability to regulate blood glucose levels through severe insulin resistance. This will ultimately lead to affected development of tissues and organs throughout the body. In addition to the physical abnormalities, leprechaunism is also characterized by endocrine system abnormalities that can lead to conditions such as hyperglycemia (high blood glucose levels), hypoglycemia (low blood glucose levels), hyperinsulemia (high blood insulin levels), and the enlargement of certain sex organs such as the penis in males, and the clitoris in females. Facial features indicative of Donohue syndrome include protuberant and low-set ears, flaring nostrils, unusually large mouth, thick lips, and widely spaced eyes. Physical features include stunted growth (including during gestation), lack of subcutaneous adipose tissue, muscle atrophy, hirsutism (excessive body hair growth), and dysplasia (nail malformation). Additionally, a condition known as acanthosis nigricans is present in affected individuals. In acanthosis nigricans, patches of skin darken and thicken to gain a velvet-like appearance. Gender specific features also include enlarged clitoris and breasts, as well as ovarian cysts in affected females, and enlarged penis in affected males. In the Journal of Pediatric Medicine, Donohue and Uchida described affected sisters whose growth appeared to have ended in the seventh month of gestation, both born alive but dying before four months of age.