Trichonodosis

Abstract

Trichonodosis is characterized by knotted hair on the distal portion of the hair shaft. This may be spontaneous or secondary to mechanical factors like vigorous scratching or combing the hair. We report a case of spontaneous trichonodosis with abnormal scalp and body hair.

INTRODUCTION

Trichonodosis is characterized by knotted hair on the distal portion of the hair shaft. This may be spontaneous or secondary to mechanical factors like vigorous scratching or combing the hair. Trichonodosis may be associated with abnormal scalp and body hair growth. The knots should be distinguished from the ova of head louse. Although the incidence of trichonodosis is common, it is reported less frequently.

CASE REPORT

A 19-year-old female patient presented with short, rough, and unruly hair on the scalp since childhood. There was history of breakage of hair beyond a particular length throughout the scalp. Patient gave a history of knots getting caught in fine-toothed comb whenever the scalp was combed with breakage of few hairs. There was no family history of similar complaints. There was no history of excessive cosmetic use or parlor activities for hair care. On examination, the scalp hairs were dry, curly, and short in length up to the nape of neck, transverse split ends (trichoschisis) were seen in majority of hairs [Figure 1]. Few hairs showed small nodules on the distal portion [Figure 2]. Hairs were sparse in temporal region [Figure 3]. Eyebrow, axillary and pubic hairs were sparse [Figure 4]. Microscopic examination of the hair shaft revealed knotted portions of hair; no other shaft abnormalities were noted except for trichoschisis at the distal portion of the shaft [Figure 5]. General and physical examination was within the normal limits. Considering the clinical findings and light microscopy a diagnosis of trichonodosis was made.

Figure 1.

Short curly hair on the scalp

Figure 2.

Small nodules on the distal portion of hair shaft

Figure 3.

Sparse hair in the temporal region

Figure 4.

Sparse eyebrow hair

Figure 5.

Trichonodosis and trichoschisis in light microscopy

DISCUSSION

Trichonodosis (knotted hair) was first described by McCarthy.[1] There are two types, one rare variety of unknown etiology involves abnormally growing scalp and body hair with spontaneous trichonodosis which is predisposed to splintering and fracturing.[2] The second commoner type, encountered in patients with normal scalp and body hair, is considered secondary to mechanical forces such as combing and brushing. The hairs in this type are dry and curly, but no abnormality in structure or growth pattern occurs.[2]

The knots are usually located on the outer third of the hair shaft. Rarely, more than one knot is found on a single hair and most were a simple half hitch knot.[2] Trichonodosis is usually associated with trichoschisis. When the hair of subjects with trichonodosis was combed or brushed, knots were observed to catch in fine toothed combs and to a lesser extent, in brushes. In those with extensive trichonodosis, one or two hairs would break off with each stroke. Breakage usually occurred at the knot, but proximal breakage and several uprooted telogen hairs were also seen. Microscopically, the fractured hairs tended to be flattened on cross section.[2]

Trichonodosis is a characteristic of long, kinky scalp hair. Kinky hair tends to be flat in cross section, whereas curly or straight hair is oval to round. These flat or ribbon-shaped hairs do not lie flat on a level surface but remain spiral.[2] When gently pulled and released, the hairs recoil into spirals. This recoiling may lead to an entanglement which, by chance, forms a knot that results in trichonodosis.[2] The natural kinky hair of Negroes consistently develops trichonodosis.

Mechanical factors such as scratching, combing, washing or friction may produce tangling and knotting of hairs. Repeated encounter with these factors results in tightening of the knots.[3] The pubic and thigh regions are most frequently involved since curliness of the hairs in those areas predisposes them to knotting. If the knots are pulled excessively tight, transverse splintering of the hair shaft and simulation of trichorrhexis nodosa may result. Not all the hairs are involved in trichonodosis. These knots resemble the ova of body, head and pubic lice and light microscopic examination is necessary for differentiation. The nodules in trichonodosis are located distally, whereas the ova are located in the proximal shaft. The location of nodules is of diagnostic value.

Acquired type of trichonodosis due to mechanical factors is a common occurrence but reported less in literature.[4,5] Spontaneous type of trichonodosis associated with abnormal scalp and body hair is a rare occurrence. This type starts at an early age and hair breaks away after a particular length due to the fracture of hair shaft at the knot. This condition persists indefinitely and is resistant to any form of treatment. Treatment for the acquired type is proper hair care practices. Trichonodosis must be considered when patients with kinky hair complain of hair loss or breakage, and the cause is not apparent.