In which condition do patients typically present with muscle rigidity and cognitive decline in a 5-year-old girl?

In evaluating a case where a 5-year-old girl presents with muscle rigidity and cognitive decline, it is particularly pertinent to consider the implications of neurological involvement associated with mitochondrial disorders, one of which is Leber Hereditary Optic Neuropathy (LHON).

However, LHON primarily affects vision and may not be directly associated with muscle rigidity or significant cognitive decline, especially at such a young age. Therefore, it would be essential to look beyond LHON when interpreting these symptoms.

Wilson's disease is a much more fitting diagnosis in this scenario. It is known to cause neurological manifestations, including muscle rigidity, dystonia, and cognitive changes due to copper accumulation in the body. Children presenting with this condition may exhibit both hepatic and neurological symptoms, including behavioral changes, learning difficulties, and movement disorders.

Glycogen storage diseases typically present with different clinical features, primarily involving muscle weakness and hypoglycemia, and are less likely to present primarily with cognitive decline and rigidity.

Mitophagy disorders can result in a variety of neurological symptoms due to mitochondrial dysfunction, but they are often associated with specific syndromes and may not be as clearly defined in their presentation as Wilson's disease.

In summary, the symptoms of muscle rigidity and cognitive decline most closely