This dictionary word of the day got me a bit anxious as it is something that is sparingly used medicine. The meaning i see if the dictionary is its use as an adjective to define something as gloomily dark; shadowy; dimly lighted or simply somber.
In health conditions something that is gloomy, dark or dusky shows up for pellagra, a discolouration of skin that is usually a condition due to the deficiency of vitamin B3 ( medically described as niacin) or its precursor, tryptophan ( something that precedes or from which a more mature or active substance is formed).
Excessive use of tryptophan, found in Cheese, Chicken, Eggs, Fish, Milk, Nuts, Peanut butter, Peanuts, Pumpkin seeds, Sesame seeds, Soy, Tofu and Turkey.
This deficiency could occur due to diet or due to malabsorption or even alchoholism. Severe conditions are caused rarely by carcinoid tumours, a tumour of the gastrointestinal tract that involves functioning of chromaffin cells.
Treatment is nutritional substitution with vitamin B3.