Introduction. Les patients atteints de neuropathie optique héréditaire de Leber (NOHL) dont la présentation clinique est atypique peuvent être faussement diagnostiqués initialement. Observation. Un frère et une sœur atteints de NOHL présentèrent une perte visuelle aiguë bilatérale dans l’enfance. La sœur fut la première atteinte et l’amélioration de sa vision commença deux mois après le début des symptômes. Sa présentation clinique ainsi qu’une anamnèse familiale négative conduisirent à un diagnostic initial erroné de névrite optique idiopathique de l’enfant. Le diagnostic correct de NOHL ne fut suspecté que quatre ans plus tard, lorsque le frère cadet de la patiente présenta une perte visuelle bilatérale aiguë, similaire à sa sœur. Une analyse de l’ADN mitochondrial confirma le diagnostic de NOHL et montra deux mutations primaires de NOHL, T14484C et G15257A. Il bénéficia aussi d’une amélioration significative de sa vision, qui débuta un mois après le début des symptômes. Conclusion. Les présentations cliniques de NOHL peuvent varier. Une NOHL devrait être suspectée chez chaque patient présentant une neuropathie optique bilatérale aiguë, même en cas d’anamnèse familiale négative.

Introduction. Leber’s hereditary optic neuropathy (LHON) is a maternally inherited disorder affecting the optic nerves in which the typical clinical presentation is subacute, painless, sequential visual loss in young adult males. Patients with LHON who have atypical clinical features may be initially misdiagnosed. Observation. An 8-year-old boy developed an acute severe bilateral optic neuropathy associated with pain and mild optic disc edema. Molecular genetic testing of his mitochondrial DNA revealed two point mutations, T14484C and G15257A. His vision began to improve within one month of onset of visual loss and eventually recovered to 20/15 in both eyes. Four years previously, his oldest sister had acutely lost vision in both eyes at age 12 years. Her young age, female gender, the bilateral visual loss associated with pain, optic disc edema, absent family history of visual loss and negative workup were felt to be most consistent with a clinical diagnosis of idiopathic optic neuritis of childhood. Her visual recovery which began within two months of visual loss further supported the diagnosis. She was retrospectively re-diagnosed with LHON after her younger brother was genetically confirmed. Conclusion. We describe two siblings with LHON whose time course from onset of visual loss to onset of visual recovery was unusually rapid. Because of other atypical features for LHON such as their young age at presentation, bilateral simultaneous visual loss and associated periorbital pain, their clinical profile appeared more typical of a demyelinating disease such as childhood optic neuritis. The first affected sibling (sister) was initially misdiagnosed. This report emphasizes that the clinical spectrum of LHON is variable and thus, LHON should be considered in any patient with an acute bilateral optic neuropathy, even in the absence of a positive family history. Correct diagnosis of this maternally inherited disorder is important for assessment of visual prognosis and appropriate genetic counseling.