General Ophthalmology Quiz 9

Yichieh Shiuey, MD | Massachusetts Eye and Ear Infirmary, Harvard Medical School

March 16, 1998
Figure 1
This is the face of a very fair skinned boy who had decreased vision in both eyes since birth. On slit lamp examination, he had iris transillumination.
Questions and Answers
1. What is the diagnosis?
Answer: Oculocutaneous albinism where the skin, hair, and eyes are all affected. In ocular albinism the predominant feature is ocular hypopigmenation.

2. What is the most likely cause of the decreased vision?
Answer: Foveal hypoplasia is almost always associated with albinism and is the cause of decreased vision.

3. What ocular examination findings may this child have?
Answer: Pendular nystagmus, iris transillumination defects, lightly pigmented fundus, foveal hypoplasia. Although, not present in this child strabismus is also common.

4. What enzyme deficiency may be responsible for these clinical features?
Answer: Tyrosinase deficiency may produce albinism because the enzyme is necessary for melanin synthesis FROM phenylalanine and tyrosine. These types of albinism are termed tyrosinase-negative. Types of albinism where tyrosinase is intact are referred to as tyrosinase-positive albinism.

5. What potentially life threatening conditions may be associated with this child's oculocutaneous findings?
Answer: Chediak-Higashi syndrome is an immune deficiency syndrome that is associated with albinism that may result in life-threatening infection. Hermansky-Pudlak syndrome is a condition associated with albinism that results in bleeding abnormalities.