Stargardt macular degeneration is a disorder belonging to the group of macular dystrophies, genetic disorders of macular degeneration that become clinically apparent during the second and third decade of life. Loss of central vision is the main presentation. The diagnosis requires a detailed physical and ophthalmological examination, an adequate family history, and genetic studies.
The clinical presentation of Stargardt macular degeneration (STGD) stems from the accumulation of lipofuscin in the retina and its progressive atrophy, occurring on the grounds of genetic mutations involving substances responsible for retinoid transport away from the outer segments of rods, one of the two types of cells essential for vision   . Unlike age-related macular degeneration (AMD), when symptoms are seen after 60 years of age, the onset of progressive central visual loss during the second and third decade of life is the distinguishing feature of SMD   . Furthermore, a delay in adaptation to dark (presumably due to atrophy of photoreceptors, in addition to lipofuscin accumulations) is frequently observed . On the basis of patterns of inheritance, STGD can be divided into autosomal recessive (STGD1), which is more common, and autosomal dominant forms (STGD3, or Stargardt-like macular degeneration and STGD4) that can be suspected when a delayed loss of central vision at any point between the second and fifth decades is seen   . Gradual loss of visual acuity often leads to blindness, like in other macular dystrophies, but abnormalities of color vision are minimal or absent in STGD, which may be used as an important distinguishing feature .
Clinical suspicion toward atypical forms of macular degeneration must exist in the presence of a juvenile onset of central vision loss and a delayed adaptation to dark. Firstly, a detailed patient history should determine the exact onset of symptoms. Similar findings in close relatives or siblings may be encountered in all types of STGD, having in mind both autosomal dominant and autosomal recessive patterns of inheritance, thus emphasizing the importance of a detailed family history . After a comprehensive patient interview, a complete ophthalmological exam is necessary. Progressive macular atrophy, with or without the appearance of yellow flecks (composed of lipofuscin) are typically observed on fundoscopy . Moreover, fluorescein angiography is a useful method to distinguish STGD1 from STGD3 by identifying a dark choroid on examination . If valid criteria for STGD exist, genetic studies are necessary to identify specific mutations responsible for the onset of this disorder. Autosomal recessive STGD1 stems from mutations in the photoreceptor cell–specific ATP-binding cassette transporter (ABCR) gene located on chromosome 1p13, whereas genes coding for elongase of very long chain fatty acids-4 (or ELOVL4) located on chromosome 6 are the underlying cause of the autosomal dominant STGD3 and STGD4  . Haplotype analysis is the recommended diagnostic method for detection of mutations in STGD.