49,XYYYY syndrome
Findings
No curated finding names 49,XYYYY syndrome yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
49,XYYYY is a rare Y chromosome number anomaly with a variable phenotype mainly characterized by moderate to severe intellectual disability, speech delay, hypotonia, and mild dysmorphic features, including facial asymmetry, hypertelorism, bilateral low set 'lop' ears, and micrognatia. Skeletal abnormalities (such as skull deformities, radioulnar synostosis, elbow flexion, clinodactyly, brachydactyly) and behavourial problems have also been associated with this condition. Genitalia are normal at birth, although hypogonadism and azoospermia has been reported in adults.
Definition from the Mondo Disease Ontology (MONDO:0020470), read 2026-09-29. CC BY 4.0.
Features
43 features
What the disease is reported to present with, and how often among people who have it — never how often a feature means the disease. HPO, annotations 2026-09-02.
- Abnormal cerebral white matter morphologyHPOHP:0002500
- Very frequent (80% to 99% of cases)
- Abnormal elbow epiphysis morphologyHPOHP:0003946
- Very frequent (80% to 99% of cases)
- Abnormal facial shapeHPOHP:0001999
- Very frequent (80% to 99% of cases)
- Abnormality of the genitourinary systemHPOHP:0000119
- Very frequent (80% to 99% of cases)
- Abnormality of the testis sizeHPOHP:0045058
- Very frequent (80% to 99% of cases)
- Atypical behaviorHPOHP:0000708
- Very frequent (80% to 99% of cases)
Show the remaining 31
- Delayed skeletal maturationHPOHP:0002750
- Very frequent (80% to 99% of cases)
- Delayed speech and language developmentHPOHP:0000750
- Very frequent (80% to 99% of cases)
- Eunuchoid habitusHPOHP:0003782
- Very frequent (80% to 99% of cases)
- External genital hypoplasiaHPOHP:0003241
- Very frequent (80% to 99% of cases)
- Finger clinodactylyHPOHP:0040019
- Very frequent (80% to 99% of cases)
- Global developmental delayHPOHP:0001263