History and clinical findings: Two patients with circumscribed alopecia on the lateral aspect of the thigh underwent a neurological investigation after medical and dermatological examinations had failed to establish the cause. Patient 1 also had neuralgia of the genitofemoral nerve after osteotomy of the iliac crest; patient 2 had insulin-dependent diabetes mellitus. Within the affected part of the skin both patients had sensory dysfunctions over the area of distribution of the cutaneous lateral femoral nerve. Patient 2 additionally had sensory dysfunctions in other areas of innervation.
Investigations: Neurogram and recordings of sensory evoked potentials revealed decreased amplitudes on the affected side, establishing the diagnosis of meralgia paresthetica.
Treatment and course: The painful neuropathy was successfully treated in both patients with carbamazepine (patient 1: 1.600 mg daily; patient 2: 900 mg daily).
Conclusion: Circumscribed alopecia can be caused by peripheral nerve lesions. It should be considered in the differential diagnosis, particularly as the cause can be easily established.