Glutaric acidemia type 1: Treatment and outcome of 168 patients over three decades

Glutaric acidemia type 1 (GA1) is a disorder of cerebral organic acid metabolism resulting from biallelic mutations of GCDH. Without treatment, GA1 causes striatal degeneration in >80% of affected children before two years of age. We analyzed clinical, biochemical, and developmental outcomes for 168 genotypically diverse GA1 patients managed at a single center over 31 years, here separated into three treatment cohorts: children in Cohort I (n = 60; DOB 2006-2019) were identified by newborn screening (NBS) and treated prospectively using a standardized protocol that included a lysine-free, arginine-enriched metabolic formula, enteral l-carnitine (100 mg/kg•day), and emergency intravenous (IV) infusions of dextrose, saline, and l-carnitine during illnesses; children in Cohort II (n = 57; DOB 1989-2018) were identified by NBS and treated with natural protein restriction (1.0-1.3 g/kg•day) and emergency IV infusions; children in Cohort III (n = 51; DOB 1973-2016) did not receive NBS or special diet. The incidence of striatal degeneration in Cohorts I, II, and III was 7%, 47%, and 90%, respectively (p < .0001). No neurologic injuries occurred after 19 months of age. Among uninjured children followed prospectively from birth (Cohort I), measures of growth, nutritional sufficiency, motor development, and cognitive function were normal. Adherence to metabolic formula and l-carnitine supplementation in Cohort I declined to 12% and 32%, respectively, by age 7 years. Cessation of strict dietary therapy altered plasma amino acid and carnitine concentrations but resulted in no serious adverse outcomes. In conclusion, neonatal diagnosis of GA1 coupled to management with lysine-free, arginine-enriched metabolic formula and emergency IV infusions during the first two years of life is safe and effective, preventing more than 90% of striatal injuries while supporting normal growth and psychomotor development. The need for dietary interventions and emergency IV therapies beyond early childhood is uncertain.

Homozygosity for a mutation affecting the catalytic domain of tyrosyl-tRNA synthetase (YARS) causes multisystem disease

Aminoacyl-tRNA synthetases (ARSs) are critical for protein translation. Pathogenic variants of ARSs have been previously associated with peripheral neuropathy and multisystem disease in heterozygotes and homozygotes, respectively. We report seven related children homozygous for a novel mutation in tyrosyl-tRNA synthetase (YARS, c.499C > A, p.Pro167Thr) identified by whole exome sequencing. This variant lies within a highly conserved interface required for protein homodimerization, an essential step in YARS catalytic function. Affected children expressed a more severe phenotype than previously reported, including poor growth, developmental delay, brain dysmyelination, sensorineural hearing loss, nystagmus, progressive cholestatic liver disease, pancreatic insufficiency, hypoglycemia, anemia, intermittent proteinuria, recurrent bloodstream infections and chronic pulmonary disease. Related adults heterozygous for YARS p.Pro167Thr showed no evidence of peripheral neuropathy on electromyography, in contrast to previous reports for other YARS variants. Analysis of YARS p.Pro167Thr in yeast complementation assays revealed a loss-of-function, hypomorphic allele that significantly impaired growth. Recombinant YARS p.Pro167Thr demonstrated normal subcellular localization, but greatly diminished ability to homodimerize in human embryonic kidney cells. This work adds to a rapidly growing body of research emphasizing the importance of ARSs in multisystem disease and significantly expands the allelic and clinical heterogeneity of YARS-associated human disease. A deeper understanding of the role of YARS in human disease may inspire innovative therapies and improve care of affected patients.

Minimizing cicatricial pemphigoid orodynia with minocycline

Cicatricial pemphigoid is a rare autoimmune blistering disease of the elderly. It predominantly affects the mucosae, causing pain and scarring. the target antigen is within the lamina lucida of the basement membrane zone. Potential complications of systemic steroid and other immunosuppressive therapy have prompted trials of other means of treatment. We describe a series of seven patients treated with minocycline, six of whom derived sustained alleviation of orodynia. Four patients developed hyperpigmentation, and two complained of gastrointestinal discomfort which necessitated cessation of minocycline. Complete steroid withdrawal was achieved in two cases. Neither the disease progression nor the response to treatment was influenced by the immunoglobulin isotype or titre. The role of minocycline as a useful adjunct to therapy is discussed.

Treatment of cicatricial pemphigoid with tetracycline and nicotinamide

Cicatricial pemphigoid is a rare autoimmune blistering disease involving predominantly mucosal areas in elderly patients. It runs a chronic relapsing course. Immunosuppressive treatments are frequently complicated by adverse effects and require careful monitoring. A 69-year-old woman is reported who responded well to a simple regimen of combined tetracycline and nicotinamide after 15 years of inadequate disease control and numerous adverse effects from immunosuppressive agents.

Natural history of keratosis pilaris

A questionnaire was sent to 83 patients in the south Buckinghamshire area, in whom a primary diagnosis of keratosis pilaris (KP) had been made within the preceding 20 years. Of the 50 questionnaires returned, one was invalid, and 49 were evaluated. The age range of patients surveyed was 18 months-25 years; 61% were female and 39% male. Age of onset of KP was within the first decade in 51%, second decade in 35%, third decade in 12%, and fourth decade in 2%. Body sites affected were the arms (92%), legs (59%), face (41%), buttocks (30%) and eyebrows (8%). Other family members were affected by KP in 39%; 55% had no family history of KP, and 6% did not know. There was a personal history of atopy in 37%, 16% had associated dry skin, and 47% had neither. A seasonal variation in the severity of KP was noted in 80% of patients; 49% of these improved in the summer and 47% worsened in the winter. Overall, KP had improved with age in 35% of patients, remained unchanged in 43%, and worsened in 22%. The mean age of improvement was 16 years.