The Dermoscopic “Chromosome Arms Sign” for Terra Firma-Forme Dermatosis.
Terra firma-forme dermatosis belongs to the group
of “dirty dermatoses” and represents a not well-known and
surely underestimated skin condition. Firstly described by Duncan,
Tschen and Knox in 1987, it accounts for a few case series in the
literature and has a still undefined aetiology.
TFFD might result from delayed keratinocyte maturation, which leads to the retention of keratinocytes/melanin within the epidermis,
but not all authors agree with this idea.
When TFFD or Duncan’s dirty dermatosis is clinically
suspected, clearance of the dermatosis follows rubbing the affected skin with 70% isopropyl alcohol. As suggested by Errichetti et al1 wiping the lesions in the
clinic may be quite embarrassing for the patients, hence the need
of other diagnostic approaches.
A 9-year-old girl presented to our clinic with the presence of a not
well-defined patch of brownish discoloration on the lateral and
frontal part of the neck. The mother stated that the lesions have
been present for the last 10-months.
The pediatrician who sends us the patient had the suspect of nevus epidermicus or akantosis nigricans. Insulinemia test
was performed and showed normal results.
On clinical observation a reticulated and pigmented not
well-defined area was seen.
The dermoscopic findings detected in our TFFD case are
in line with data reported in previous cases,2-8 thus confirming the
reliability of dermoscopy in assisting the diagnosis of this condition by showing this extremely peculiar chromosome arms aspect.
Dermatol Open J. 2021; 6(1): 18-20. doi: 10.17140/DRMTOJ-6-146