RESUMEN
Background: Hyperargininemia is a rare inherited metabolic disorder of the urea cycle with an autosomal recessive transmission. It occurs due to a deficiency of the enzyme arginase I and causes progressive neurological damage. Very few cases are diagnosed in adulthood, with the majority being diagnosed before the age of 4. Currently, this condition is diagnosed by a mass spectrometry technique in neonatal screening, which has been implemented in Portugal since 2007; births before that were not screened for this entity. Case description: We present a case of a 23-year-old woman referred to the internal medicine and neurology departments with a history of two hospital admissions for rhabdomyolysis at the age of 18, consanguineous parents, learning difficulties and multiple falls since the age of 8. In addition, the patient also had behavioural changes so she had psychological counselling at school, but lacked family support. Neurological examination showed mild proximal paraparesis, and spastic and paraparetic gait. The aetiological study revealed a pathological variant in homozygosity ARG1 and increased blood levels of arginine. Therefore, the diagnosis of hyperargininemia was confirmed. Conclusions: Compared to other urea cycle disorders, hyperargininemia is the rarest one. It is important to recognise the characteristic clinical features and diagnose it early because a favourable outcome can be achieved with appropriate treatment. This case shows a delayed diagnosis of hyperargininemia and highlights the importance of the internist's role in diagnosing rare diseases. LEARNING POINTS: Hyperargininemia is a rare hereditary metabolic disease of the urea cycle and the rarest of the disorders affecting this cycle.The diagnosis is almost always made within the first four years of life and very few are diagnosed in adulthood.Early diagnosis is essential to reduce the progression of neurological damage, through appropriate treatment.
RESUMEN
Pompe disease is a rare metabolic disorder with available enzymatic replacement therapy. Contrasting with the classic infantile form, the others subtypes have a heterogeneous presentation that makes an early and accurate diagnosis difficult. We conducted a prospective, multicenter, observational study to identify undiagnosed patients. During a one-year period, patients followed in Portuguese neuromuscular outpatient clinics with proximal muscle weakness affecting upper and/or lower limbs, hyperCKemia in two or more determinations or hypotonia and hyperCKemia, were screened for acid α-glucosidase deficiency by dried blood spots. Lysosomal acid-alpha-1,4-glucosidase activity was determined by tandem mass spectrometry and positive results were confirmed by molecular study. From the 99 patients screened, Pompe disease was confirmed in 4, with age of onset ranging from 2.5 to 48 years, all with limb girdle muscle weakness, corresponding to a frequency of 4% in our cohort and 4.9% of limb girdle muscle weakness. Screening for Pompe disease in high risk populations, using dried blood spots, was already performed in some European populations. Apart from two negative Scandinavian studies, positive cases were confirmed in 2.8-7.9% of patients presenting with limb girdle muscle weakness and in 0-2.5% with isolated hyperCKemia.
