Distal phalangeal erythema in an infant with biallelic PDSS1 mutations: Expanding the phenotype of primary Coenzyme Q10 deficiency.

We report a detailed clinical examination in a patient with primary coenzyme Q10 deficiency caused by biallelic mutations in the PDSS1 gene who presented clinical features of mitochondrial encephalopathy associated with pulmonary hypertension, livedo reticularis and particularly, chronic distal phalangeal erythema. Laboratory testing showed elevated plasma lactate and 3-methyl-glutaconic and tricarboxylic aciduria. Supplementation with high dose of coenzyme Q10 was not effective to control disease progression and the patient died at the age of 3 years old because of a progressive multisystem disorder. Cutaneous involvement in mitochondrial disease is heterogenous, including proliferative, inflammatory, and dystrophic changes among others. The coexistence in our case of phalangeal erythema, livedo reticularis, and pulmonary hypertension suggests microvascular dysfunction as a possible underlying mechanism. This is the first reported patient with PDSS1 mutations presenting with 3-methyl-glutaconic aciduria and distal phalangeal erythema, expanding the phenotype of primary coenzyme Q10 deficiency.