The term refers to a set of one or more pale transverse bands extending all the way across the nail, parallel to the lunula.

[1] As in Terry's and half-and-half nails, the pattern is thought to be formed by bands of localized edema exerting pressure on the surrounding capillaries.

[3][5] The appearance of Muehrcke's lines is associated specifically with marked hypoalbuminemia (serum albumin ≤ 2.2 g/dL) indicating decreased protein synthesis, which may occur during periods of metabolic stress (e.g. systemic infection, trauma, AIDS, chemotherapy), or in hypoalbuminemic states such as the nephrotic syndrome or dietary protein deficiency.

[3][6][7][8][9] The lines remain visible as long as protein intake is inadequate or synthesis is impaired, and they should disappear upon return to normal function.

In a study published in BMJ, he examined patients with known chronic hypoalbuminemia and healthy volunteers, finding that the appearance of multiple transverse white lines was a highly specific marker for low serum albumin (no subject with the sign had SA over 2.2 g/dL), was associated with severity of the underlying condition, and disappeared upon successful treatment (corticosteroids in nephrotic syndrome) or direct infusion of HSA.