Pseudoxanthoma elasticum confirmed by genetic analysis but not by skin biopsy: a case report and review of the literature.

In patients with angioid streaks, additional investigations are useful to identify underlying systemic disease, unless age and short peripapillary streaks are indicative of senile streaks as an isolated abnormality. In middle-aged or young adults with angioid streaks and no obvious systemic disease, the possibility of a hemoglobulinopathy or pseudoxanthoma elasticum (PXE) as etiologic entities should be investigated. Hemoglobinopathies can be excluded based on blood screening and the absence of typical ocular fundus changes, such as retinal vessel tortuosity. This allows making a presumed clinical diagnosis of PXE in patients with angioid streaks, based on exclusion of a hemoglobinopathy, and on the presence of extensive angioid streaks, peau d'orange, crystalline bodies and comet tail lesions. For confirmation of PXE, the gold standard was dermatologic examination and skin biopsy, but since the last decade molecular diagnosis is available. In rare cases, PXE can be diagnosed using molecular techniques in patients with apparently normal skin and negative skin biopsies, as demonstrated in this case and another case published in 2011.