Types
DIFFUSE ALOPECIA
Congenital diffuse alopecia
- Trichorrhexis nodosa: A hair shaft deformity characterized by the development of weak points in the shaft due to physical/chemical trauma in genetically predisposed individuals
- Pili torti: The hair shaft is flattened and has multiple twists which lead to fragile hair that breaks easily
- Monilethrix(beaded hair): Autosomal dominant disorder with beaded hair shafts which break easily, close to the scalp, a few months after birth
- Genetic syndromes: Menkes disease, Netherton's syndrome etc.
Acquired diffuse alopecia
- Androgenetic alopecia : It is a progressive, nonscarring alopecia that affects the regions of the scalp with the most androgen-sensitive hair follicles, resulting in a characteristic pattern of balding (bitemporal scalp in men and vertex and frontal scalp in women).
- Terminal hair is converted into vellus hair. In men recession of the frontal hairline near the temples and thinning over the vertex occurs. In women, the scalp hair is generally diffuse but more so in the vertex area
- Differential diagnosis of androgenetic alopecia includes Diffuse alopecia areata , Telogen effluvium
PATCHY NON SCARRING ALOPECIA
Congenital circumscribed alopecia
- Temporal triangular alopecia: A well-defined oval/triangular patch of alopecia in the temporal part of the scalp. Usually seen before 5 years of age. It mimics alopecia areata and is differentiated from it by the presence of vellus hair and the absence of exclamation point hair
Acquired circumscribed alopecia
- Alopecia areata :is an unpredictable usually patchy, non-scarring hair loss condition. It affects men and women equally and any hair bearing surface may be affected
- The characteristic initial lesion is commonly a round or oval, totally bald, smooth patch involving the scalp on any hair bearing area on the body
- A frequent feature in alopecia areata patch is Exclamation mark hairs that are broken short hairs tapering proximally. The pull test may be positive at the margins of the patch indicating very active disease
- Alopecia araeata can occur as diffuse loss of hair form scalp but spares the grey hair
Various patterns of distribution
- Ophiasis: hair loss localized to the back and sides of the scalp( so called from its resemblance to snake)
- Sisiapho: sparing of the sides and back of the scalp
- Extensive alopecia areata: hair loss affecting > 50% of the scalp
- Alopecia universalis : All hair-bearing sites are affected, Total hair loss from whole body (mimics telogen effluvium)
- Alopecia totalis: Complete baldness
- Nail involvement (up to 40% of cases): nail pitting, onycholysis, Beau lines, etc.
- Other autoimmune disorders may be present (e.g., vitiligo, autoimmune disorders of the thryoid, etc.)
- Differential diagnosis includes Tinea capitis, Trichotillomania( Compulsive pulling out of one's own hair with ill-defined patchy hair loss and hairs of different lengths) and Secondary syphilis