White Piedra: An Uncommon Superficial Fungal Infection of Hair

Abstract

White piedra is a superficial fungal infection of hair caused by Trichosporon species. It presents clinically as white nodules encasing the hair shafts and may lead to increased fragility. It can usually be differentiated easily from clinically similar conditions based on clinical and microbiologic features. We report a case of white piedra of scalp hair in a 32-year-old female caused by T. ovoides, diagnosed using clinical, trichoscopic, microbiologic and molecular methods. In this case, trichoscopy acted as an interface between clinical and microbiologic examination, obviating the need for hair shaft microscopy. The genus Trichosporon contains 6 species of clinical significance viz., T. asahii, T. asteroides, T. cutaneum, T. inkin, T. mucoides, and T. ovoides, which cannot be differentiated based on their morphologic characteristics. A genotypic identification using molecular methods helped determine the causative species. It was treated successfully with oral itraconazole and topical ketoconazole.

Established Facts

• White piedra is a superficial fungal infection of hairs caused by Trichosporon species.

• Traditionally, clinical and microbiologic examination forms the basis of diagnosis.

Novel Insights

• Trichoscopy can act as an interface between clinical and microscopic examination, obviating the need of microscopy, by helping in differentiating from common differential diagnoses.

• Genotypic identification using molecular methods helps identify the causative species of Trichosporon.

• Systemic azole therapy can be an effective option in patients who do not wish to shave hair.

Introduction/Literature Review

The Spanish word “piedra” means stone and justifies its usage to denote conditions characterized by presence of hard nodules along the hair shaft, namely white and black piedra. These two are distinguishable clinically, based on the colour and consistency of nodules, their anatomic localization, and fragility of hair.

White piedra (tinea nodosa / trichosporonosis nodosa / trichomycosis nodularis) is an asymptomatic, superficial fungal infection caused by Trichosporonspecies [1]. Nodules in white piedra, as the name indicates, are white or beige in colour and relatively softer than those of black piedra, which are black and stone hard. Hair fragility is increased in black piedra, but is not a common feature of white piedra. In addition, white piedra more commonly involves the hair of face, axillae and pubic region, rarely involving scalp in contrast to black piedra [2]. Herein, we report a case of white piedra of scalp in a young female caused by Trichosporon ovoides, confirmed by molecular analysis.

Case Report

A 32-year-old woman presented for evaluation of nodular thickening of scalp hair which became more apparent after hair wetting. It was associated with increased hair breakage for the past 2–3 months. The patient also gave history of repeatedly tying wet hairs after washing. No other body parts were involved and none of the family members were affected.

Examination revealed a normal-looking scalp with abundant, long hair, without any evidence of sparseness. Individual hair shafts showed barely visible but well-palpable, white to beige nodules, distributed at irregular intervals, and not easily movable along the hair shaft (Fig. 1). Hair pull test was negative and Wood's lamp examination did not show any fluorescence. Ex-vivo trichoscopy (AM73915MZT Dino-lite Edge 3.0 digital microscope) revealed white amorphous material locally encasing the hair (Fig. 2).

Fig. 1.

White to beige nodules, distributed at irregular intervals along the hair shaft.

Fig. 2.

White amorphous material locally encasing the hair on ex-vivo trichoscopic examination (polarised view ×150).

The clipped hair was also used to prepare 10% potassium hydroxide (KOH) mount which at 400× magnification revealed clusters of arthrospores, cemented in the extracellular matrix, firmly adherent to the hair shaft, with focal presence of brown pigment (Fig. 3). Culture on Sabouraud's Dextrose Agar (SDA) without cycloheximide grew white cerebriform colonies with characteristic “butter cream frosting” (Fig. 4), while no growth was seen on SDA with cycloheximide. Standard tease mounts from the growth using Lactophenol Cotton Blue (LCB) on microscopic examination at 400× magnification showed multiple branching hyphae with blastoconidia (Fig. 5).

Fig. 3.

Clusters of arthrospores cemented in an extracellular matrix, firmly adherent to the hair shaft with focal presence of brown pigment visualized on microscopic examination of 10% KOH mount at ×400 magnification. KOH, potassium hydroxide.

Fig. 4.

White cerebriform colonies with characteristic “butter cream frosting” on culture in SDA without cycloheximide. SDA, Sabouraud's Dextrose Agar.

Fig. 5.

Multiple branching hyphae with blastoconidia visualized on standard tease mounts from the growth using Lactophenol Cotton Blue on microscopic examination at ×400 magnification.

The culture inoculated on SDA was subjected to genotypic identification. DNA extracted from culture using commercially available DNA extraction kit (HiYield Genomic DNA Kit; Real Biotech Corporation, Taiwan) was further subjected to PCR and DNA sequencing using pan-fungal primers, ITS1 (5′TCCGTAGGTGAACCTGCGG-3′) and ITS4 (3′-TCCTCCGCTTATTGATATGC-5′). The sequence analysis was performed and compared with the sequences deposited in GenBank by using the BLAST program (https://www.ncbi.nlm.nih.gov/blast/Blast.cgi). The isolate was identified as Trichosporon ovoides, showing >99% homology with known isolate of Trichosporon (GenBank: KY105753.1).

On the basis of history, clinical examination, microscopic analysis, and molecular identification, a diagnosis of white piedra was made. The patient did not agree to cutting hair or shaving them, hence was prescribed oral itraconazole 200 mg daily with topical ketoconazole 2% for 4 weeks. There was significant reduction in the number and size of nodules at 1 month and absence after 2 months of therapy. There was on recurrence over the following 6 months.

Discussion

White piedra is caused by yeast-like fungi belonging to the genus Trichosporon, which has now been documented to be a part of human microbiome. Initially, the organism was named T. beigelii after Beigel who described it in 1865. Subsequently, it was realised that T. beigelii is not a single species but rather a species complex and hence was subdivided into 6 species, including Trichosporon ovoides, Trichosporon inkin, Trichosporon asahii, Trichosporon mucoides, Trichosporon asteroides, and Trichosporon cutaneum. White piedra of scalp is most commonly caused by T. ovoides & T. cutaneum, while that of pubic hairs is caused by T. inkin. Phenotypic switching from yeast to hyphae, metabolic plasticity from carbon to nitrogen sources, biofilm formation, immune evasion, secretion of lytic enzymes and the cell wall composition contribute to the pathogenicity of Trichosporon spp [3]. While white piedra is the most common superficial infection caused by Trichosporon, the fungus can also infect skin and nails, causing tinea-like skin lesions and onychomycosis, respectively. It can present as disseminated cutaneous trichosporonosis characterized by widespread papules or purpuric nodules in immunocompromised patients [4]. Recently, a case of invasive cutaneous trichosporonosis caused by T. asahii in a patient with toxic epidermal necrolysis has been reported [5]. In addition to the skin, it can infect lungs and central nervous system causing hypersensitivity pneumonitis and meningitis, respectively [5].

The differential diagnosis of white piedra includes black piedra, trichobacteriosis, nits (pediculosis capitis) and hair casts. The differentiation from black piedra has been discussed above. Trichobacteriosis axillaris, capitis, or pubis can be distinguished based on history of hyperhidrosis, bromhidrosis, stained clothes and detection of fluorescence on Wood's lamp [6]. Microscopic examination of concretions from cases of trichobacteriosis reveal cocci and diphtheroids. Nits are easily differentiated from nodules of white piedra as they are always attached at an angle to the hair shaft, do not encase the hair shaft, and are closer to the scalp than nodules of white piedra. Simultaneous visualization of head louse makes the diagnosis easier, in addition to history of itching reported by the patient [2]. Hair casts can be easily pulled along the hair shaft as compared to nodules of white piedra which are immobile. Microscopic examination can easily differentiate the two.

Tying of wet hairs could have predisposed our patient to develop white piedra as high humidity, curly and long hairs are known predisposing factors. Initial adherence of arthroconidia, blastoconidia, or mycelia to the hair shaft initiates nodule formation, which further mature by deposition of cement-like extracellular substance. Biochemical analysis of white piedra nodules has shown them to be composed of carbon, oxygen, sodium, and magnesium. The nodules of black piedra have sulphur in addition, which could be responsible for their hardness [7].

Shaving the infected hair is curative and most effective treatment but is unacceptable due to social, cultural, or religious factors, especially in women. Antifungals have variable efficacy in eliminating hair shaft concretions without shaving. Topical antifungals like ketoconazole, ciclopirox olamine shampoo, selenium sulphide, precipitated sulphur in petrolatum, zinc pyrithione, and amphotericin B lotion have been used with successful outcomes. Amongst oral antifungals, azoles (itraconazole) eliminate scalp carriage and infection, hence are considered as first line treatment due to the evidence of presence of intrafollicular organisms [1]. This uncommon case of white piedra of scalp hair caused by Trichosporon ovoides, confirmed by molecular methods is reported to sensitize the clinicians towards this possibility.

Statement of Ethics

The study was conducted ethically in accordance with the World Medical Association Declaration of Helsinki. The subject has given her written informed consent to publish the case (including publication of images). Institutional Ethical Review Board approval was not required for this study in accordance with national guidelines.

Conflict of Interest Statement

The authors have no conflicts of interest to declare. None of the authors report any form of support and financial involvement. There are no nonfinancial relationships (personal, political, or professional) that may potentially influence the writing of the manuscript. Dr. Chander Grover is a member of the Editorial Board of “Skin Appendage Disorders.”

Funding Sources

The authors did not receive any funding.

Author Contributions

	Contributor
	1	2	3	4
Concepts	✓	✓	✓
Design	✓	✓	✓
Definition of intellectual content	✓	✓	✓
Literature search	✓	✓		✓
Clinical studies	✓	✓		✓
Experimental studies	N/A	N/A		✓
Data acquisition	✓	✓	✓	✓
Data analysis	✓	✓		✓
Statistical analysis	N/A	N/A
Manuscript preparation	✓	✓	✓	✓
Manuscript editing	✓	✓	✓
Manuscript review	✓	✓	✓
Guarantor		✓