Rare diseases · Sign or symptom
Gynecomastia
Enlarged male breast
HP:0000771
What it means
Abnormal development of large mammary glands in males resulting in breast enlargement.
Rare diseases that can present with this56
Very common80–99%
17- 46,XY difference of sex development-adrenal insufficiency due to CYP11A1 deficiency
- 46,XY partial gonadal dysgenesis
- 49,XXXYY syndrome
- 49,XYYYY syndrome
- Aromatase excess syndrome
- Borjeson-Forssman-Lehmann syndrome
- Cerebellar ataxia-hypogonadism syndrome
- Hypogonadism-mitral valve prolapse-intellectual disability syndrome
- Hypogonadotropic hypogonadism-severe microcephaly-sensorineural hearing loss-dysmorphism syndrome
- Hypoinsulinemic hypoglycemia and body hemihypertrophy
- Inherited isolated adrenal insufficiency due to partial CYP11A1 deficiency
- Kennedy disease
- Male hypergonadotropic hypogonadism-intellectual disability-skeletal anomalies syndrome
- Obesity due to congenital leptin deficiency
- Obesity due to leptin receptor gene deficiency
- Retinitis pigmentosa-intellectual disability-deafness-hypogonadism syndrome
- Wilson-Turner syndrome
Common30–79%
16- 48,XXXY syndrome
- 48,XXYY syndrome
- 49,XXXXY syndrome
- ANE syndrome
- Congenital adrenal hyperplasia due to 17-alpha-hydroxylase deficiency
- Congenital adrenal hyperplasia due to 3-beta-hydroxysteroid dehydrogenase deficiency
- Hyposmia-nasal and ocular hypoplasia-hypogonadotropic hypogonadism syndrome
- Intellectual disability-cataracts-calcified pinnae-myopathy syndrome
- Isochromosomy Yp syndrome
- Isochromosomy Yq syndrome
- Normosmic congenital hypogonadotropic hypogonadism
- Partial androgen insensitivity syndrome
- POEMS syndrome
- Prolactinoma
- TSH-secreting pituitary adenoma
- Xq27.3q28duplication syndrome
Sometimes5–29%
20- 2p15p16.1microdeletion syndrome
- 45,X/46,XY mixed gonadal dysgenesis
- 46,XY difference of sex development due to 17-beta-hydroxysteroid dehydrogenase 3 deficiency
- 46,XY difference of sex development due to isolated 17,20-lyase deficiency
- 6q terminal deletion syndrome
- African trypanosomiasis
- Alström syndrome
- Carney complex
and 12 more in this range
The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Gynaecomastia
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Start free with EleplanThis page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.