has part has part characteristic of inheres in has modifier Abnormality of the philtrum Smooth philtrum Decreased depth of philtrum Indistinct philtrum There is a spectrum of this finding from total absence of the philtral ridges to a some prominence of the ridges. The central groove varies from absent to shallow. Normal values for the frequency of smooth philtrum are available. Grading of the smoothness of the philtrum, used in the assessment of Fetal Alcohol Syndrome, has been developed. This finding is greatly influenced by the facial expression, and care should be taken to evaluate the philtrum when the face is in a neutral position. A smooth philtrum can be associated with a Long philtrum. However, the two findings should be coded separately. Shallow philtrum HP:0000319 Simple philtrum Flat skin surface, with no ridge formation in the central region of the upper lip between the nasal base and upper vermilion border. HP:0000299 Philtrum, smooth Flat philtrum HP:0000323 UMLS:C1142533 HP:0004663 flat abnormal philtrum