[Meralgia paresthetica. A rare differential diagnosis of circumscribed alopecia]

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.

Neurogram and recordings of sensory evoked potentials revealed decreased amplitudes on the affected side, establishing the diagnosis of meralgia paresthetica.

The painful neuropathy was successfully treated in both patients with carbamazepine (patient 1: 1.600 mg daily; patient 2: 900 mg daily).

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.