Medically Reviewed by Dr. K on 10 March 2021
Table of contents
Dermatologists use the term hypotrichosis to describe a disease in which there is no hair formation. Unlike alopecia, which describes hair loss where there was previously hair growth, hypotrichosis describes hair loss where there was never any hair growth, to begin with. Hypotrichosis (plural) are illnesses that affect people from the moment they are born and normally last throughout their lives.
The bulk of hypotrichosis is caused by genetic abnormalities or embryonic growth defects. Genetic hypotrichosis comes in a variety of shapes and sizes. Affected patients often have other physical or emotional issues in addition to a loss of hair. Hypotrichosis is a symptom that can occur in a variety of conditions, including Graham-Little syndrome, Ofuji syndrome, cartilage-hair hypoplasia, Jeanselme, and Rime hypotrichosis, Marie Unna hypotrichosis, and metaphyseal chondrodysplasia, to name a few.
Our understanding of whether and how genetic mutations affect hair loss and other symptoms are improving as our understanding of the human genome improves. However, while we may have a good understanding of the genetics and biochemistry of hypotrichosis, handling them is extremely difficult. The majority of hypotrichosis-related diseases have no known cure.
A few types of hypotrichosis are worth noting, either because they are relatively normal or because they provide insight into hair follicles.
Aplasia cutis congenital, also known as congenital aplasia, is a developmental condition in which the skin does not completely grow as an embryo forms for unknown reasons. An infant may have a patch of skin that looks like an open wound or an ulcer when they are born. This flaw is most often seen at the back of the scalp, in the middle of the “whorl pattern" of hair development. The skin will scab over and the infant will be left with a scar if the defect is minor.
This will happen in the womb, and all that is visible after birth is a strip of scalp with no hair follicles. If a baby is born with a big congenital aplasia, an operation to remove the affected region and cover the skin is normally needed.
Since the exposed wound is a possible source of hemorrhage and inflammation, this is always achieved with a sense of urgency. The quicker it heals, the better.
Alopecia triangularis (triangular alopecia) is a syndrome that is similar to congenital aplasia. It affects a triangular patch of skin and hair above the temples and is normally visible from birth. In a few people, the skin struggles to develop hair follicles in this region for unexplained causes. Although babies do not have open ulcers like those that have aplasia cutis congenital, the long-term effect is similar: a bald spot where hair does not grow. The infected area can be surgically removed or hair follicles from anywhere on the scalp can be inserted.
In terms of hair loss patterns, congenital atrichia, also known as papular atrichia, is a rare condition. It was the first human hair loss disorder to be linked to a single gene mutation, according to researchers. Although the disease is often referred to as hypotrichosis, it is not a true hypotrichosis. Congenital atrichia patients will be born with a full head of hair, much like every other infant. However, they lose all of their hair in early infancy and it never grows again.
Normal hair follicles depend on chemical contact between two groups of cells: modified keratinocytes, which make up the outer skin epithelium, and modified fibroblasts, also known as dermal papilla cells. To ensure hair growth and cycling, these two cell groups must communicate with each other through biochemical signals. To keep the mechanism running, the cells must remain in direct touch with one another. Without receiving signals from the other cell population, one cell population cannot produce hair.
The exact cause of congenital atrichia is unknown, although it appears that the two cell types divide when the hair follicles reach their first resting (telogen) state in early childhood.
As hair follicles enter the resting process of the hair cycle, the epithelial cell portion of the hair follicle retracts, as it should. Normally, the dermal papilla cells will accompany the retracting epithelial cells, maintaining close contact, but this is not the case in congenital atrichia.
Instead, the dermal papilla cells are left deep inside the skin, too far away from the epithelial cells to communicate with. A new anagen growth process cannot exist without this contact, and hair will never grow again. Although congenital atrichia is a genetic disorder that runs in families, it is also a gene defect that can occur naturally in certain embryos born to parents who do not have it. Any patients with alopecia Universalis actually have congenital atrichia.
Reference on 2.3.2021:
- Agrawal, N. K. (2013, October). Management of hirsutism. Indian Journal of Endocrinology and Metabolism, 17(Suppl 1), S77–S82
- De Raeve, L., & Keymolen, K. (2011, June). Congenital hypertrichosis lanuginosa in a father and son [Abstract]. Archives of Dermatology, 147(6), 746–747
- Hayashi, R., Yoshida, K., Abe, R., Niizeki, H., & Shimomura, Y. (2017, January). First Japanese case of congenital generalized hypertrichosis with a copy number variation on chromosome 17q24. Journal of Dermatological Science, 85(1), 63–65
- Hypertrichosis. (2016, February)
- Hypertrichosis lanuginosa congenita (2014, October 23)
- Lapidoth, M., Adatto, M., Cohen, S., Ben-Amitai, D., & Halachmi, S. (2014, January). Hypertrichosis in Becker's nevus: Effective low-fluence laser hair removal [Abstract]. Lasers in Medical Science, 29(1), 191–193
- Pavone, P., Praticò, A. D., Falsaperla, R., Ruggieri, M., Zollino, M., Corsello, G., & Neri, G. (2015, August 5). Congenital generalized hypertrichosis: The skin as a clue to complex malformation syndromes. Italian Journal of Pediatrics, 41(1), 55