Schinzel syndrome, also known as ulnar-mammary syndrome, is a rare inherited disorder characterized by abnormalities of the bones of the hands and forearms in association with underdevelopment (hypoplasia) and dysfunction of certain sweat (apocrine) glands and/or the breasts (mammary glands). Abnormalities affecting the hands and/or forearms range from underdevelopment of the bone in the tip of the fifth finger (hypoplastic terminal phalanx) to underdevelopment or complete absence of the bone on the outer aspect of the forearm (ulna).
In addition, certain sweat glands such as those located under the arms may be underdeveloped or absent, resulting in diminished ability or inability to sweat (perspire). In some cases, the breasts (mammary glands) may also be underdeveloped or absent; as a result, affected females exhibit a diminished ability or an inability to produce milk (lactate).
The range and severity of physical abnormalities associated with Schinzel syndrome varies greatly among affected individuals; some cases may be very mild, while others may be more severe.