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Classification of Hair Loss In Men

Norwood Class A
The Norwood Class A patterns are characterized by a front to back progression of hair loss. Norwood Class As lack the connecting bridge across the top of the scalp and generally have more limited hair loss in the crown, even when advanced.

The Norwood Class A Patterns

The Norwood Class A patterns are less common than the regular pattern (<10%), but are significant because of the fact that, since the hair loss is most dramatic in the front, the patients look very bald even when the hair loss is minimal. Men with Class A hair loss often seek surgical hair restoration early, as the frontal bald area is not generally responsive to medication and the dense donor area contrasts and accentuates the baldness on top. Fortunately, Class A patients are excellent candidates for hair transplantation.

In both Norwood patterns, the sides and back tend to resist androgenetic changes, although the sides may exhibit significant thinning in old age (senile alopecia.)

Diffuse Patterned and Unpatterned Alopecia
There are two other types of genetic hair loss in men not often considered by doctors, “Diffuse Patterned Alopecia” and “Diffuse Unpatterned Alopecia”. These pose a significant challenge both in diagnosis and in patient management. Understanding these conditions is crucial to the evaluation of hair loss in both men and women, particularly those that are young when the diagnoses may be easily missed, as they may indicate that a patient is not a candidate for surgery.

Diffuse Patterned Alopecia (DPA) is an androgenetic alopecia manifested as diffuse thinning in the front, top and crown, with a stable permanent zone. In DPA, the entire top of the scalp gradually miniaturizes (thins) without passing through the typical Norwood stages. Diffuse Unpatterned Alopecia (DUPA) is also androgenetic, but lacks a stable permanent zone and affects men much less often than DPA. DUPA tends to advance faster than DPA and ends up in a horseshoe pattern resembling the Norwood class VII. However, unlike the Norwood VII, the DUPA horseshoe can look almost transparent due to the low density of the back and sides. Differentiating between DPA and DUPA is very important because DPA patients often make good transplant candidates, whereas DUPA patients almost never do, as they eventually have extensive hair loss without a stable zone for harvesting.

Diffuse Patterned Alopecia (DPA)

The progression of male hair loss in Diffuse Patterned Alopecia (DPA) and Diffuse Unpatterned Alopecia (DUPA). In DUPA, the sides thin significantly as well.

Additional Hair Loss Characteristics in Men
One of the patterns that is not well described in the Hamilton-Norwood classification is the hair loss that commences at the crown (back of the head) and enlarges centrifugally while maintaining to a very good degree the frontal hairline. This pattern is that which afflicts the heir to the throne of England, Prince Charles, and yet, were he not surrounded by a legion of cameras, many individuals would be unaware of his condition.