This contribution presents 14 dermatology-related eponyms that honor the patients who helped define the clinical entities and disorders that bear their names or initials. These clinical entities and disorders include: (1) anti-La antibodies, (2) anti-Ro antibodies, (3) anti-Sm antibodies, (4) B-K mole syndrome, (5) Hela cells, (6) Carrion disease, (7) Christmas disease, (8) Cowden syndrome, (9) Hageman disease, (10) Hartnup disease, (11) Mortimer malady, (12) rickettsiosis, (13) Schamroth sign, and (14) Trousseau syndrome.

The interaction between angiotensin-converting enzyme 2 (ACE2) and the sodium-dependent Broad neutral Amino acid Transporter 1 (B0AT1), encoded by the SLC6A19 gene, is increasingly recognized as pivotal in both physiological and pathological contexts. B0AT1 facilitates neutral amino acid transport and nutrient absorption, while ACE2 regulates vascular homeostasis and inflammation through the renin-angiotensin system. Mutations in SLC6A19 are implicated in Hartnup disease, a metabolic disorder characterized by defective amino acid transport. However, the cellular mechanisms underlying Hartnup disease-causing mutations' impact on B0AT1 and ACE2 function remain unclear. This study evaluated the subcellular localization and trafficking of 18 Hartnup disease-causing B0AT1 variants using experimental approaches including biochemical assays and In Silico analysis. The impact of these variants on ACE2 trafficking and plasma membrane targeting was also assessed to elucidate their interplay. Nine B0AT1 variants (R57C, G93R, R95P, R178Q, L242P, G284R, S303L, D517G, P579L) were found to be retained in the endoplasmic reticulum, impairing their trafficking to the plasma membrane. These variants were distributed across multiple B0AT1 structural domains. Importantly, several of these ER-retained variants, particularly R178Q and S303L, significantly disrupted ACE2 intracellular trafficking and its localization to the plasma membrane, indicating a direct effect on ACE2 subcellular targeting. The findings reveal that Hartnup disease-causing mutations can lead to ER retention of B0AT1, which in turn has a variable effect on ACE2 trafficking. This disruption likely contributes to Hartnup disease pathogenesis by impairing amino acid transport and may influence ACE2-mediated physiological functions beyond the renin-angiotensin system. Understanding these molecular mechanisms enhances insight into ACE2-B0AT1 interactions and could inform future therapeutic strategies and biomarker development for related disorders. Further research is needed to explore these pathways and their implications in disease.

This contribution presents 14 dermatology-related eponyms that honor the patients who helped to define the clinical entities and disorders that bear their names or initials. These clinical entities and disorders include: (1) anti-La antibodies, (2) anti-Ro antibodies, (3) anti-Sm antibodies, (4) B-K mole syndrome, (5) HeLa cells, (6) Carrion disease, (7) Christmas disease, (8) Cowden syndrome, (9) Hageman disease, (10) Hartnup disease, (11) Mortimer malady, (12) rickettsiosis, (13) Schamroth sign, and (14) Trousseau syndrome.

In adults, inborn metabolic diseases are often missed in routine diagnostic settings due to a low level of suspicion. A patient in their twenties was admitted for an apparent acute exacerbation of anxiety disorder. Medical treatment was unsuccessful, and presumed catatonic psychosis was treated by electroconvulsive treatment. The patient was referred to neurology with reduced level of consciousness, mutism with no targeted movements, obvious anxiety and tetraspasticity, eczema, and reduced body weight. EEG was normal; repeat brain MRI showed progressive atrophy and leukoencephalopathy. Autoimmune encephalitis was assumed and treated with plasma exchange, high-dose glucocorticoids, and intravenous immunoglobulin. Repeated CSF analyses remained normal. Metabolic workup showed hyperaminociduria, low neutral amino acids, and undetectable tryptophane. Whole-exome sequencing and segregation analysis revealed compound heterozygous, pathogenic and a novel, likely pathogenic variant in the SLC6A19 gene: c.718C>T, p.(Arg240*) and c.170G>A, p.(Arg57His). Diagnosing Hartnup disease, high-protein diet, and niacin supplementation led to rapid considerable improvement. At 4 months, plasma amino acids were normal; communication and behavior were age-adequate; and spasticity had almost resolved, but polyneuropathy was unchanged. Metabolic workup and whole-exome sequencing are recommended in rapidly progressive neuropsychiatric disease, especially with additional neurologic signs and when standard treatment fails.