Wooly Hair

WOOLLY HAIR (Charles Rip-Botha)

Woolly hair usually implies a benign condition best described as normal hair with a tight curl, which is sometimes frizzy resembling Negroid hair. As one ages the extent of the curl may reduce.

Woolly hair syndrome is distinguishable from normal curly hair in that the hair shaft demonstrates characteristic exaggerated tight often frizzy coils. The affected hair shafts frequently possess a narrower oval cross section with prominent axial twisting. The hair may be difficult to comb due to the narrow diameter curls (generally not exceeding 0.05cm). Trichorrhexis nodosa may be present resulting in increased severance.

The hair growth pattern suggests that shafts may achieve limited maximum length due to a shorter anagen phase.

There is a clear difference between localised woolly hair known as woolly hair nevus. Woolly hair syndrome is an inherited condition distinguishable as either dominant or recessive. In the autosomal dominant variation there is an inconstant degree of tight curling present throughout the scalp. The autosomal recessive form (present at birth) displays abnormally curly hairshafts of fine texture which may occasionally be lighter in colour.  Autosomal dominant woolly hair is not characteristically affected by pigment variation although there have been reports of hypopigmentation.   Woolly hair syndrome may be evident in siblings with normal parents. It has been suggested that the sudden unexpected appearance of an autosomal dominant trait in a lineage is the result of mutation.

Woolly hair nevus which may be lighter in colour, is a circumscribed variant of the syndrome that appears in childhood or adolescence.  In half of all reported cases this condition is associated with epidermal or melanocytic nevus.

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FURTHER DISCUSSION


Woolly hair is usually tightly coiled over all or part of the scalp, in an individual not of Negroid origin. The clinical syndromes of which woolly hair is a feature have been confused by many authors. It remains possible, however, that woolly hair is a feature of syndromes not yet characterized.

Classification and etiology

Autosomal dominant woolly hair. This has been reported in six generations of Rhineland family, suggesting autosomal dominant inheritance. 2- Autosomal recessive woolly hair. The genetic evidence is inconclusive but the condition has occurred in siblings whose parents were normal. Autosomal recessive inheritance or a germline mutation are probable. 3- Symmetrical circumscribed allotrichia also known as acquired progressive kinking appears to be distinct syndrome. 4- Wolly hair neavus. This is a circumscribed developmental defect, present at birth, and apparently not genetically determined. The basis for the woolly appearance in these variants is not clear. Many different features contribute to the range of hair types seen in different races and these have been quantified. However, no racial appearance corresponds entirely with woolly hair and although we suspect that the cross-sectional morphology and cortical make-up are determinants, at present we do not know.

Autosomal dominant woolly hair.
(a) Pathology in some pedigrees the shaft diameter in affected individuals is reduced. The hair is fragile and may show trichorrhexis nodosa. Pili torti and pili annulati have been reported as associated defects, but in different families.
(b) Clinical features. Excessively curly hair is evident at birth or in early infancy, it has sometimes been described as Negroid in appearance. The degree of variation in severity within a family is inconstant. There is no consistent association with any hair color. The hair shaft may be twisted. Eye defects may be found. In some cases the hair is brittle and breaks readily, probably as a result of increased susceptibility to weathering. The hair in sites other than the scalp is usually normal. Four cases of diffuse woolly hair dystrophy have been described a mother and daughter and two other unrelated individuals. Abnormal hairs were mixed diffusely within normal population of scalp hair, possibly suggesting a chimera or an X-linked dominant inheritance with mosaicism along Blascko’s line, although inheritance is nuclear. Microscopy revealed weathering and alternate light and dark bands using reflected light, secondary to twisting.
Autosomal recessive woolly hair.

Pathology. There is a marked reduction in the diameter of hair shafts which may be poorly pigmented. The hair is brittle and on scanning electron microscopy shows signs of cuticular damage. Clinical features. So few cases have been reported that generalizations are unwarranted. In there cases fine, tightly curled, poorly pigmented hair was present from birth, in two of them the hair never grew more than 2 or 3cm. eyebrows and body hair were sparse.

Symmetrical circumscribed allotrichia: Whisker hair
History and nomenclature. Among cases reported as woolly hair naevus  are some of which Norwood has proposed the term, whisker hair,  but which are identical with the cases reported by Knierer  as symmetrical circumscribed allotrichia.
Clinical features:
 From adolescence onwards the affected hair forms an irregular band extending around the edge of the scalp from above the ears towards the occipital region and becomes coarse and whisker-like. Many people believe that whisker hair is synonymous with acquired progressive kinking.
Woolly hair neavus. Pathology. The hair in the affected region of the scalp is finer than elsewhere. Electron microscopy of the abnormal hair has shown absent cuticle and trichorrhexis nodosa indicative of weathering. Light microscopy in other cases has failed to reveal any abnormality.
Clinical features. The hair in a circumscribed area of the scalp is tightly curled from birth or from early infancy. The size of the affected areas usually increases only proportionately with general growth, but it may extend for 3 or 4 years. The abnormal hair may be slightly more place in colour than that of the rest of the scalp. In over half of the reported cases a pigmented or epidermal naevus has been present but not in the same sit. Woolly hair  has been reported in association with ocular defects in three instance. The first was a persistent papillary membrane in a subject with a Woolly hair naevus. The second showed the same papillary fault with a naevus, but with additional congenital paralysis of the superior oblique muscle, cataracts and focal retinal dysplasia. Most recently, a case of autosomal dominant woolly hair with congenital cataract and Coats, disease has been reported. The association with ocular disease justifies early ophthalmic examination in those presenting with woolly hair. Gurault et al. described eight infants presenting with intractable diarrhea, dysmorphism, immunodeficiency and woolly hair. Only two of the infants were related and the authors favoured neither a genetic nor infective mechanism as the cause. Each presented within the first 6 months and most within 3 weeks of birth. Only three survived.

Dr Sajjad Ahir MD LTTS (Consultant Dermatologist) Pakistan

The President 2014

 

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