Coexisting trichorrhexis nodosa and pili annulati: a case report of hair shaft abnormalities in a Syrian family.

Introduction: Pili annulati (PA) and trichorrhexis nodosa (TN) are rare genetic hair disorders. PA presents with sparkly, spotted hair due to air-filled cavities in the cortex, mainly affecting the scalp. TN causes brittle, breakable hair shafts, often due to physical or chemical damage. Case Presentation: A 23-year-old Syrian woman presented with glistening, brittle hair and whitish nodules since puberty, reminiscent of TN. Trichoscopy confirmed TN alongside PA, displaying characteristic dark-light bands. Interestingly, TN breakage occurred within the PA bands. Her aunt displayed similar TN patterns. Microscopy revealed ring-like structures and a 'thrust paint brush' appearance, indicative of TN, within PA-affected regions. Management included avoidance of hair treatments and prescription of vitamins and minoxidil to enhance hair strength and density. Discussion: PA is usually congenital and autosomal dominant, often without causing hair fragility. However, some cases report fragility, particularly in light bands. While PA is typically benign, its combination with TN underscores the complexity of hair shaft disorders. Only five such cases exist. Proposed causes for PA and TN include genetic factors and hair shaft abnormalities. PA's fragility may stem from band stiffness differences and lower cysteine content. Treatment is typically unnecessary, but avoiding excessive heat styling is advised. Conclusion: This case highlights the rare co-occurrence of PA and TN, emphasizing the need for further research into their relationship and potential systemic associations. Understanding the underlying mechanisms is crucial for informing treatment and counseling patients effectively, especially considering the rarity of this association.