Nail changes can be a clue in diagnosing some vitamin deficiencies, as in this patient's nail beading. Beads that seem to drip down the nail like wax are associated with vitamin B deficiencies and some endocrine conditions (eg. diabetes mellitus, thyroid disorders and Addison disease). Brown-gray nails may be associated with vitamin B12 deficiency. A central nail ridge may be caused by iron deficiency, folic acid deficiency, or protein deficiency. Koilonychia (spoon nail) is associated with iron deficiency and protein deficiency (especially sulfur-containing amino acids, such as cysteine or methionine).