Brittle Hair and Mental Deficit Syndrome

At a glance

A genetic disorder characterized by abnormal hair and mental deficiency.

Synonym

Sabinas Brittle Hair Syndrome.

Incidence

Less than 20 cases have been described. Affected families have been found initially only in the remote village of Sabinas in northern Mexico, which explains the synonymous name of the disorder. In 2009, two additional cases (twins) were reported from Nuevo Laredo (about 200 km away from Sabinas).

Genetic inheritance

Autosomal recessive inheritance. Affected families most often demonstrate parental consanguinity and the manifestation of the disease in siblings of both sexes support autosomal recessive inheritance.

Pathophysiology

Examination of hair fibers demonstrates a reduction in the cuticular layer and a collapsed cortex. The cystine and sulfur amino acids contents of the hair are reduced, while the copper-to-zinc ratio is increased. No specific histopathologic changes in the central nervous system have been described.

Diagnosis

Made by the clinical appearance (persistent congenital scalp hypotrichosis) and by morphologic and biochemical abnormalities of hair fibers.

Clinical aspects

The disorder is characterized by dry, brittle, fragile scalp hair, sparse eyebrows and eyelashes (which may be excessively curved), a variable degree of developmental delay (IQ between 50 and 60), and normal stature. Affected newborns may be identified by persistent scalp hypotrichosis. In the postpubertal period, individuals have reduced or virtually absent pubic and axillary hair, but otherwise normal postpubertal sexual development and hormone levels. Microscopically, the hair presents with irregular structure and breaks within the hair shaft, loss of cuticle, and marked fraying in areas with previous fracture (trichoschisis). Many patients are said to never require a haircut (due to breakage of the hairs). Polarizing microscopy reveals a diagnostic pattern of alternating light and dark banding, which, due to its appearance, has been called “tiger tail banding” or “zig-zag” pattern. Moderate to severe onychodystrophy with proximal splitting and cracking is present in all patients. Many patients have significant maxillary hypoplasia and crowded teeth. Few patients had ophthalmologic symptoms such as pigmentary retinopathy unilateral congenital tortuosity of the retinal vessels or pale optic discs. The condition is considered to be a nonphotosensitive form of ☞Trichothiodystrophy. Features in common include autosomal recessive inheritance, abnormal hair, and associated mental retardation.

Precautions before anesthesia

Assess the significance of maxillary hypoplasia and dental status with regards to airway management. Evaluate the patient’s neurologic status. Developmental delay may cause agitation and stress in the perioperative period; thus, anxiolytic and sedative premedication and/or presence of a parent (or primary caregiver) for induction of anesthesia may be beneficial. Otherwise, routine preoperative assessment is advised.

Anesthetic considerations

Facial dysmorphism is mild, thus airway management ...