- rod/cone dystrophy - a progressive eye condition, which can lead to blindness
- obesity, childhood-onset with fat distributed particularly around the trunk (middle of body)
- polydactyly (extra fingers and/or toes)
- hypogenitalism (underdeveloped genitals)
- mild-to-severe learning difficulties (see entry Learning Disability)
- renal abnormalities and impaired renal function
- Endocrine disturbances that involve pituitary, thyroid, adrenal glands, the ovaries and testes (may lead to subfertility).
Secondary features may include:
- speech problems
- developmental delay (see entry Global Developmental Delay)
- behavioural abnormalities
- eye abnormalities, including strabismus (cross-eyed), cataracts, and astigmatism (abnormally shaped eyeball)
- brachydactyly (short fingers and/or thumbs)
- syndactyly (digits joined together)
- diabetes mellitus
- dental and roof of mouth abnormalities
- cardiovascular anomalies (high blood pressure, abnormal heart valves)
- hepatic (liver) problems
- olfactory dysfunction (lack of ability to smell)
- Situs inversus (misplacement of internal organs - eg mirror-image).
In children with BBS, night-blindness usually occurs by seven to eight years of age and total blindness is typical by mid to late adolescence.