Ulnar-mammary syndrome

Ulnar-mammary syndrome (UMS), also known as Schinzel syndrome or ulnar-mammary syndrome of Pallister, is a rare genetic disorder characterized by a combination of upper limb defects predominantly affecting the ulnar (pinky finger) side of the hand and forearm, along with abnormalities of the breast and apocrine glands. The condition is caused by mutations in the TBX3 gene located on chromosome 12q24.1, which encodes a transcription factor critical for limb and mammary gland development. The limb abnormalities range widely in severity, from absence or hypoplasia of the fifth finger or ulna to more significant reduction defects of the forearm. Mammary and apocrine gland involvement includes hypoplasia or aplasia of the breasts and nipples, as well as diminished or absent axillary hair and apocrine gland secretion. Additional features may include delayed puberty, genital anomalies (particularly in males, such as micropenis or cryptorchidism), obesity, short stature, and dental anomalies. Some affected individuals also have pyloric stenosis or other structural abnormalities. Ulnar-mammary syndrome is present from birth, though some features such as breast underdevelopment and delayed puberty may not become apparent until adolescence. The condition shows significant intrafamilial and interfamilial variability, meaning that even within the same family, affected individuals can have very different combinations and severities of symptoms. There is no cure for UMS; management is supportive and symptom-based. This may include orthopedic interventions or surgery for limb anomalies, hormone therapy for delayed puberty or hypogonadism, and surgical correction of breast hypoplasia if desired. Genetic counseling is recommended for affected families given the autosomal dominant inheritance pattern.

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